dvwa

Regi -explicit

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
 android:background="#FAFAFA"
 android:layout_width="match_parent"
 android:layout_height="match_parent">
 
<LinearLayout
 android:orientation="vertical"
 android:gravity="center_horizontal"
 android:padding="24dp"
 android:layout_width="match_parent"
 android:layout_height="wrap_content">

 <ImageView
 android:id="@+id/imgProfileMain"
 android:layout_width="120dp"
 android:layout_height="120dp"
 android:src="@android:drawable/ic_menu_camera"
 android:contentDescription="Profile Image"
 android:layout_marginBottom="24dp"
 android:background="@drawable/circle_bg"
 android:scaleType="centerCrop" />

 <TextView
 android:id="@+id/tvTitle"
 android:text="User Registration"
 android:textSize="28sp"
 android:textStyle="bold"
 android:textColor="#3F51B5"
 android:layout_marginBottom="24dp"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content" />

 <EditText
 android:id="@+id/etName"
 android:layout_width="match_parent"
 android:layout_height="48dp"
 android:background="@drawable/edittext_bg"
 android:padding="12dp"
 android:hint="Enter your full name"
 android:inputType="textPersonName"
 android:textColor="#212121"
 android:textSize="16sp" />

 <EditText
 android:id="@+id/etEmail"
 android:layout_width="match_parent"
 android:layout_height="48dp"
 android:background="@drawable/edittext_bg"
 android:padding="12dp"
 android:hint="Enter your email address"
 android:inputType="textEmailAddress"
 android:textColor="#212121"
 android:textSize="16sp"
 android:layout_marginTop="16dp" />

 <RadioGroup
 android:id="@+id/rgGender"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:orientation="horizontal"
 android:layout_marginTop="20dp">

 <RadioButton
 android:id="@+id/rbMale"
 android:text="Male"
 android:textColor="#3F51B5"
 android:textSize="16sp"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content" />

 <RadioButton
 android:id="@+id/rbFemale"
 android:text="Female"
 android:textColor="#3F51B5"
 android:textSize="16sp"
 android:layout_marginStart="24dp"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content" />
 </RadioGroup>

 <Spinner
 android:id="@+id/spCountry"
 android:layout_width="match_parent"
 android:layout_height="48dp"
 android:layout_marginTop="20dp"
 android:background="@drawable/edittext_bg"
 android:padding="8dp" />

 <Button
 android:id="@+id/btnDob"
 android:layout_width="match_parent"
 android:layout_height="48dp"
 android:text="Select Date of Birth"
 android:textColor="#FFFFFF"
 android:backgroundTint="#3F51B5"
 android:textSize="16sp"
 android:layout_marginTop="20dp" />

 <TextView
 android:id="@+id/tvDob"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:textColor="#757575"
 android:textSize="16sp"
 android:gravity="center"
 android:layout_marginTop="8dp" />

 <ProgressBar
 android:id="@+id/pbLoading"
 android:layout_width="48dp"
 android:layout_height="48dp"
 android:layout_marginTop="24dp"
 android:visibility="gone"
 android:indeterminateTint="#3F51B5" />

 <Button
 android:id="@+id/btnSubmit"
 android:layout_width="match_parent"
 android:layout_height="48dp"
 android:text="Submit"
 android:textColor="#FFFFFF"
 android:backgroundTint="#00796B"
 android:textSize="16sp"
 android:layout_marginTop="24dp" />

 </LinearLayout>

</ScrollView>

Activity_next.xml:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:gravity="center"
 android:padding="24dp"
 android:background="#FAFAFA"
 android:layout_width="match_parent"
 android:layout_height="match_parent">

 <ImageView
 android:id="@+id/imgProfileNext"
 android:layout_width="120dp"
 android:layout_height="120dp"
 android:src="@android:drawable/ic_menu_camera"
 android:contentDescription="Profile Image"
 android:layout_marginBottom="24dp"
 android:background="@drawable/circle_bg"
 android:scaleType="centerCrop" />

 <TextView
 android:id="@+id/tvResult"
 android:textColor="#222222"
 android:textSize="20sp"
 android:lineSpacingExtra="6dp"
 android:textAlignment="center"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"/>

 <ProgressBar
 android:id="@+id/pbLoadingNext"
 android:layout_width="48dp"
 android:layout_height="48dp"
 android:visibility="gone"
 android:layout_marginTop="20dp"
 android:indeterminateTint="#3F51B5" />
</LinearLayout>

MainAcitivity.java:

package com.example.registration_form;
import androidx.appcompat.app.AppCompatActivity;
import android.app.DatePickerDialog;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.*;
import java.util.Calendar;

public class MainActivity extends AppCompatActivity implements DatePickerDialog.OnDateSetListener {

 private EditText etName, etEmail;
 private RadioGroup rgGender;
 private Spinner spCountry;
 private Button btnDob, btnSubmit;
 private TextView tvDob;
 private ProgressBar pbLoading;
 private String selectedGender = "";
 private String selectedDate = "";

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);

 etName = findViewById(R.id.etName);
 etEmail = findViewById(R.id.etEmail);
 rgGender = findViewById(R.id.rgGender);
 spCountry = findViewById(R.id.spCountry);
 btnDob = findViewById(R.id.btnDob);
 btnSubmit = findViewById(R.id.btnSubmit);
 tvDob = findViewById(R.id.tvDob);
 pbLoading = findViewById(R.id.pbLoading);

 String[] countries = {
 "Select Country",
 "United States",
 "Canada",
 "United Kingdom",
 "Australia",
 "India",
 "Germany",
 "France",
 "Japan"
 };

 ArrayAdapter<String> adapter = new ArrayAdapter<>(this,
 android.R.layout.simple_spinner_item, countries);
 adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
 spCountry.setAdapter(adapter);

 rgGender.setOnCheckedChangeListener((group, checkedId) -> {
 RadioButton rb = findViewById(checkedId);
 if (rb != null) selectedGender = rb.getText().toString();
 });

 btnDob.setOnClickListener(v -> {
 Calendar calendar = Calendar.getInstance();
 DatePickerDialog dpd = new DatePickerDialog(
 MainActivity.this,
 MainActivity.this,
 calendar.get(Calendar.YEAR),
 calendar.get(Calendar.MONTH),
 calendar.get(Calendar.DAY_OF_MONTH));
 dpd.show();
 });

 btnSubmit.setOnClickListener(v -> {
 pbLoading.setVisibility(View.VISIBLE);

 String name = etName.getText().toString().trim();
 String email = etEmail.getText().toString().trim();
 String country = spCountry.getSelectedItem().toString();

 Intent intent = new Intent(MainActivity.this, NextActivity.class);
 intent.putExtra("name", name);
 intent.putExtra("email", email);
 intent.putExtra("gender", selectedGender);
 intent.putExtra("country", country);
 intent.putExtra("dob", selectedDate);

 startActivity(intent);

 pbLoading.setVisibility(View.GONE);
 });
 }

 @Override
 public void onDateSet(DatePicker view, int year, int month, int dayOfMonth) {
 selectedDate = String.format("%d-%02d-%02d", year, month + 1, dayOfMonth);
 tvDob.setText("Selected Date: " + selectedDate);
 }
}

NextActivity.java:
package com.example.registration_form;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.TextView;

public class NextActivity extends AppCompatActivity {
 private TextView tvResult;
 private ProgressBar pbLoadingNext;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_next);

 tvResult = findViewById(R.id.tvResult);
 pbLoadingNext = findViewById(R.id.pbLoadingNext);

 pbLoadingNext.setVisibility(View.VISIBLE);
 tvResult.setVisibility(View.GONE);

 new Handler().postDelayed(() -> {
 String name = getIntent().getStringExtra("name");
 String email = getIntent().getStringExtra("email");
 String gender = getIntent().getStringExtra("gender");
 String country = getIntent().getStringExtra("country");
 String dob = getIntent().getStringExtra("dob");

 String displayText = "User Details\n\n" +
 "Name: " + (name.isEmpty() ? "N/A" : name) + "\n" +
 "Email: " + (email.isEmpty() ? "N/A" : email) + "\n" +
 "Gender: " + (gender.isEmpty() ? "N/A" : gender) + "\n" +
 "Country: " + (country.equals("Select Country") ? "N/A" : country) + "\n" +
 "Date of Birth: " + (dob.isEmpty() ? "N/A" : dob);

 tvResult.setText(displayText);
 pbLoadingNext.setVisibility(View.GONE);
 tvResult.setVisibility(View.VISIBLE);
 }, 1500);
 }
}

Implicit

MainActivity.java
package com.example.myapplication;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {
 private Button browseButton, dialButton, smsButton, shareButton, emailButton, shareDataButton, buttonOpenSecond;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);

 browseButton = findViewById(R.id.browseButton);
 dialButton = findViewById(R.id.dialButton);
 smsButton = findViewById(R.id.smsButton);
 shareButton = findViewById(R.id.shareButton);
 emailButton = findViewById(R.id.emailButton);
 shareDataButton = findViewById(R.id.shareDataButton);
 buttonOpenSecond = findViewById(R.id.buttonOpenSecond);

 browseButton.setOnClickListener(v -> {
 String url = "https://www.google.com";
 Intent browseIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
 startActivity(browseIntent);
 });

 dialButton.setOnClickListener(v -> {
 Intent dialIntent = new Intent(Intent.ACTION_DIAL, Uri.parse("tel:+913979484100"));
 startActivity(dialIntent);
 });

 smsButton.setOnClickListener(v -> {
 Intent smsIntent = new Intent(Intent.ACTION_SENDTO);
 smsIntent.setData(Uri.parse("smsto:" + Uri.encode("+913979484100")));
 smsIntent.putExtra("sms_body", "Lalalalalala");
 startActivity(smsIntent);
 });

 shareButton.setOnClickListener(v -> {
 Intent shareIntent = new Intent(Intent.ACTION_SEND);
 shareIntent.setType("text/plain");
 shareIntent.putExtra(Intent.EXTRA_TEXT, "hjejkhekjh");
 startActivity(Intent.createChooser(shareIntent, "Share via"));
 });

 emailButton.setOnClickListener(v -> {
 Intent emailIntent = new Intent(Intent.ACTION_SENDTO);
 emailIntent.setData(Uri.parse("mailto:hehaho@gmail.com"));
 emailIntent.putExtra(Intent.EXTRA_SUBJECT, "give placement");
 emailIntent.putExtra(Intent.EXTRA_TEXT, "10lpa minimum needed!!!!!!!");
 startActivity(emailIntent);
 });

 shareDataButton.setOnClickListener(v -> {
 Intent intent = new Intent(Intent.ACTION_SEND);
 intent.setType("text/plain");
 intent.putExtra(Intent.EXTRA_TEXT, "This is the text data to share with other apps!");
 startActivity(Intent.createChooser(intent, "Share text via"));
 });

 buttonOpenSecond.setOnClickListener(v -> {
 Intent intent = new Intent(MainActivity.this, SecondActivity.class);
 startActivity(intent);
 });
 }
}

SecondActivity.java:
package com.example.receiverapp;
import androidx.appcompat.app.AppCompatActivity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;

public class SecondActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView txtreceive;
        txtreceive=findViewById(R.id.txtreceive);
        Intent getintent;
        getintent=getIntent();
        String val=getintent.getStringExtra(Intent.EXTRA_TEXT);
        txtreceive.setText(val);
    }
}

AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">
    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.ReceiverApp"
        tools:targetApi="31">
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>

            <intent-filter>
                <action android:name="android.intent.action.SEND"/>
                <category android:name="android.intent.category.DEFAULT"/>
                <data android:mimeType="text/plain"/>
            </intent-filter>
        </activity>
    </application>

</manifest>

File Storage(ext & int)

MainActivity.java:
package com.example.myapplication;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.Environment;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

public class MainActivity extends AppCompatActivity {
 private String storedText;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);

 EditText editText = findViewById(R.id.editText);
 TextView textView = findViewById(R.id.textView);

 Button internalStoreBtn = findViewById(R.id.internalStoreBtn);
 Button internalLoadBtn = findViewById(R.id.internalLoadBtn);
 Button externalStoreBtn = findViewById(R.id.externalStoreBtn);
 Button externalLoadBtn = findViewById(R.id.externalLoadBtn);

 String extStorageState = Environment.getExternalStorageState();

 internalStoreBtn.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 String currentText = editText.getText().toString();
 try (FileOutputStream fos = openFileOutput("messagefile", MODE_PRIVATE);
 OutputStreamWriter writer = new OutputStreamWriter(fos)) {
 writer.write(currentText);
 writer.flush();
 Toast.makeText(getApplicationContext(), "Message saved", Toast.LENGTH_LONG).show();
 editText.setText("");
 } catch (IOException e) {
 e.printStackTrace();
 }
 }
 });

 internalLoadBtn.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 try (FileInputStream fis = openFileInput("messagefile");
 InputStreamReader reader = new InputStreamReader(fis)) {

 char[] buffer = new char[250];
 int charRead;
 StringBuilder stringBuilder = new StringBuilder();

 while ((charRead = reader.read(buffer)) > 0) {
 String data = String.copyValueOf(buffer, 0, charRead);
 stringBuilder.append(data);
 }
 Toast.makeText(getApplicationContext(), "Message read", Toast.LENGTH_LONG).show();
 textView.setText(stringBuilder.toString());
 } catch (FileNotFoundException e) {
 e.printStackTrace();
 } catch (IOException e) {
 e.printStackTrace();
 }
 }
 });

 externalStoreBtn.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 if (Environment.MEDIA_MOUNTED.equals(extStorageState)) {
 File myFile = new File(getExternalFilesDir("mydir"), "sample.txt");
 String currentText = editText.getText().toString();

 try (FileOutputStream fos = new FileOutputStream(myFile);
 OutputStreamWriter writer = new OutputStreamWriter(fos)) {

 writer.write(currentText);
 writer.flush();
 Toast.makeText(getApplicationContext(), "Message saved to external storage", Toast.LENGTH_LONG).show();
 editText.setText("");
 System.out.println(getExternalFilesDir("mydir"));
 } catch (IOException e) {
 e.printStackTrace();
 }
 }
 }
 });

 externalLoadBtn.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 if (Environment.MEDIA_MOUNTED.equals(extStorageState) || Environment.MEDIA_MOUNTED_READ_ONLY.equals(extStorageState)) {
 File myFile = new File(getExternalFilesDir("mydir"), "sample.txt");

 try (FileInputStream fis = new FileInputStream(myFile);
 InputStreamReader isr = new InputStreamReader(fis);
 BufferedReader reader = new BufferedReader(isr)) {

 StringBuilder stringBuilder = new StringBuilder();
 String line;

 while ((line = reader.readLine()) != null) {
 stringBuilder.append(line).append("\n");
 }

 Toast.makeText(getApplicationContext(), "Message read from external storage", Toast.LENGTH_LONG).show();
 textView.setText(stringBuilder.toString());

 } catch (IOException e) {
 e.printStackTrace();
 }
 }
 }
 });

 }
}

Animation

MainAcitivity.java
package com.example.myapplication;
import androidx.appcompat.app.AppCompatActivity;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Color;
import android.graphics.ColorMatrix;
import android.graphics.ColorMatrixColorFilter;
import android.os.Bundle;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity2 extends AppCompatActivity {

 Button btnRotate, btnTranslate, btnScaling,
 btnFadeIn, btnFadeOut, btnBounce, btnGrey,
 btnInvert;
 ImageView imageView;
 boolean isGrey = false;
 boolean isInverted = false;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main2);

 imageView = findViewById(R.id.imageView);
 btnRotate = findViewById(R.id.btnRotate);
 btnTranslate = findViewById(R.id.btnTranslate);
 btnScaling = findViewById(R.id.btnScaling);
 btnFadeIn = findViewById(R.id.btnFadeIn);
 btnFadeOut = findViewById(R.id.btnFadeOut);
 btnBounce = findViewById(R.id.btnBounce);
 btnGrey = findViewById(R.id.btnGrey);
 btnInvert = findViewById(R.id.btnInvert);

 btnRotate.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 Animation rotate = AnimationUtils.loadAnimation(getApplicationContext(),
 R.anim.rotate);
 imageView.startAnimation(rotate);
 }
 });

 btnTranslate.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 Animation translate = AnimationUtils.loadAnimation(getApplicationContext(),
 R.anim.translate);
 imageView.startAnimation(translate);
 }
 });

 btnScaling.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 Animation scale = AnimationUtils.loadAnimation(getApplicationContext(),
 R.anim.scale);
 imageView.startAnimation(scale);
 }
 });

 btnFadeIn.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 Animation fadeIn = AnimationUtils.loadAnimation(getApplicationContext(),
 R.anim.fade_in);
 imageView.startAnimation(fadeIn);
 }
 });

 btnFadeOut.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 Animation fadeOut = AnimationUtils.loadAnimation(getApplicationContext(),
 R.anim.fade_out);
 imageView.startAnimation(fadeOut);
 }
 });

 btnBounce.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 Animation bounce = AnimationUtils.loadAnimation(getApplicationContext(),
 R.anim.bounce);
 imageView.startAnimation(bounce);
 }
 });

 btnGrey.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 Bitmap originalBitmap = BitmapFactory.decodeResource(
 getResources(),R.drawable.killua);

 Bitmap grayscaleBitmap = Bitmap.createBitmap(originalBitmap.getWidth(),
 originalBitmap.getHeight(),
 originalBitmap.getConfig());

 if(isGrey){
 imageView.setImageBitmap(originalBitmap);
 isGrey = false;
 }

 else{
 for(int x = 0; x < originalBitmap.getWidth();x++){
 for(int y = 0; y < originalBitmap.getHeight();y++){
 int pixel = originalBitmap.getPixel(x,y);
 int alpha = Color.alpha(pixel);
 int gray = (Color.red(pixel) + Color.blue(pixel) + Color.blue(pixel)) / 3;
 grayscaleBitmap.setPixel(x,y,Color.argb(alpha,gray,gray,gray));
 }
 }
 imageView.setImageBitmap(grayscaleBitmap);
 isGrey = true;
 }
 }
 });

 btnInvert.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 Bitmap originalBitmap = BitmapFactory.decodeResource(
 getResources(),R.drawable.killua);

 Bitmap grayscaleBitmap = Bitmap.createBitmap(originalBitmap.getWidth(),
 originalBitmap.getHeight(),
 originalBitmap.getConfig());

 if(isGrey){
 imageView.setImageBitmap(originalBitmap);
 isGrey = false;
 }

 else{
 for(int x = 0; x < originalBitmap.getWidth();x++){
 for(int y = 0; y < originalBitmap.getHeight();y++){
 int pixel = originalBitmap.getPixel(x,y);
 int alpha = Color.alpha(pixel);
 int red = 255-Color.red(pixel);
 int blue = 255 - Color.blue(pixel);
 int green = 255 - Color.green(pixel);
 grayscaleBitmap.setPixel(x,y,Color.argb(alpha,red,green,blue));
 }
 }
 imageView.setImageBitmap(grayscaleBitmap);
 isGrey = true;
 }
 }
 });

 }
}

audio video

MainActivity.java
package com.example.myapplication;
import androidx.appcompat.app.AppCompatActivity;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.MediaController;
import android.widget.Toast;
import android.widget.VideoView;

public class MainActivity extends AppCompatActivity {
    VideoView vv;
    Button play,pause,stop,vplay;
    MediaPlayer mp;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        play=findViewById(R.id.play);
        pause=findViewById(R.id.pause);
        stop=findViewById(R.id.stop);
        vplay=findViewById(R.id.vplay);
        vv=findViewById(R.id.vv);

        play.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mp == null) {
                    mp=MediaPlayer.create(getApplicationContext(),R.raw.sample);
                    mp.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
                        @Override
                        public void onCompletion(MediaPlayer mp) {
                            mp.release();
                        }
                    });
                    mp.start();
                    Toast.makeText(getApplicationContext(),"Playing",Toast.LENGTH_LONG).show();
                }
            }
        });

        pause.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(mp!=null){
                    mp.pause();
                    Toast.makeText(getApplicationContext(),"Audio paused",Toast.LENGTH_LONG).show();
                }
            }
        });

        stop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(mp!=null){
                    mp.release();
                    mp=null;
                    Toast.makeText(getApplicationContext(),"Video stopped",Toast.LENGTH_LONG).show();
                }
            }
        });

        vplay.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String path="android.resource://"+getPackageName()+"/"+R.raw.video;
                Uri uri=Uri.parse(path);
                vv.setVideoURI(uri);
                MediaController mc= new MediaController(MainActivity.this);
                mc.setAnchorView(vv);
                vv.setMediaController(mc);
                vv.start();
            }
        });
    }
}

GPS

AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools">
 <uses-permission android:name="android.permission.INTERNET" />
 <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
 <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
 <application
 android:allowBackup="true"
 android:dataExtractionRules="@xml/data_extraction_rules"
 android:fullBackupContent="@xml/backup_rules"
 android:icon="@mipmap/ic_launcher"
 android:label="@string/app_name"
 android:roundIcon="@mipmap/ic_launcher_round"
 android:supportsRtl="true"
 android:theme="@style/Theme.Gps"
 tools:targetApi="31">
 <activity
 android:name=".MainActivity"
 android:exported="true">
 <intent-filter>
 <action android:name="android.intent.action.MAIN" />
 <category android:name="android.intent.category.LAUNCHER" />
 </intent-filter>
 </activity>
 </application>
</manifest>

MainActivity.java:
package com.example.gps;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.content.ContextCompat;
import android.Manifest;
import android.content.pm.PackageManager;
import android.location.Address;
import android.location.Geocoder;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import java.io.IOException;
import java.util.List;
import java.util.Locale;

public class MainActivity extends AppCompatActivity implements LocationListener {

    private LocationManager lm;
    Button btnlocation;
    TextView txtlocation;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        txtlocation = findViewById(R.id.txtlocation);
        btnlocation = findViewById(R.id.btnlocation);

        if (ContextCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(MainActivity.this,
                    new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, 100);
        }

        btnlocation.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getLocation();
            }
        });
    }

    private void getLocation() {
        lm = (LocationManager) getApplicationContext().getSystemService(LOCATION_SERVICE);
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION)
                != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this,
                Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return;
        }
        lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 5000, 100, MainActivity.this);
    }

    @Override
    public void onLocationChanged(@NonNull Location location) {
        Toast.makeText(getApplicationContext(),location.getLongitude()
                +  " " +location.getLatitude(),Toast.LENGTH_LONG).show();
        Geocoder geocoder = new Geocoder(MainActivity.this, Locale.getDefault());
        try {
            List <Address> addresses = geocoder.getFromLocation(location.getLatitude(), location.getLongitude(), 1);
            String address = addresses.get(0).getAddressLine(0);
            txtlocation.setText(address);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

volleyball

build.grade.kts:
 implementation("com.android.volley:volley:1.2.1")

AndroidManifest.xml:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools">
 <uses-permission android:name="android.permission.INTERNET"/>
 <application
 android:allowBackup="true"
 android:dataExtractionRules="@xml/data_extraction_rules"
 android:fullBackupContent="@xml/backup_rules"
 android:icon="@mipmap/ic_launcher"
 android:label="@string/app_name"
 android:roundIcon="@mipmap/ic_launcher_round"
 android:supportsRtl="true"
 android:theme="@style/Theme.Volley"
 tools:targetApi="31">
 <activity
 android:name=".MainActivity"
 android:exported="true">
 <intent-filter>
 <action android:name="android.intent.action.MAIN" />
 <category android:name="android.intent.category.LAUNCHER" />
 </intent-filter>
 </activity>
 </application>
</manifest>
MainActivity.java:
package com.example.volley;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public class MainActivity extends AppCompatActivity {

    Button btnString, btnJson;
    TextView txtdata;
    String links = "https://www.w3schools.com/xml/note.xml";
    String Jsonlinks = "https://mocki.io/v1/7d6d5cdb-04bf-4df6-8e0c-5e0a70069eb4";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        txtdata = findViewById(R.id.textView);
        btnString = findViewById(R.id.btnString);
        btnJson = findViewById(R.id.btnJson);
        RequestQueue queue = Volley.newRequestQueue(getApplicationContext());

        btnString.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                StringRequest stringRequest = new StringRequest(Request.Method.GET, links, new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        txtdata.setText(response);
                    }
                }, new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        error.printStackTrace();
                    }
                });
                queue.add(stringRequest);
            }
        });

        btnJson.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Request.Method.GET,
                        Jsonlinks, null,
                        new Response.Listener<JSONArray>() {
                            @Override
                            public void onResponse(JSONArray response) {
                                StringBuffer buffer = new StringBuffer();
                                for (int i = 0; i < response.length(); i++) {
                                    try {
                                        JSONObject obj = response.getJSONObject(i);
                                        buffer.append("Roll no.: " + obj.getInt("roll") + "\n" +
                                                "Name: " + obj.getString("name") + "\n" +
                                                "Email: " + obj.getString("email") + "\n\n");
                                    } catch (JSONException e) {
                                        throw new RuntimeException(e);
                                    }
                                }
                                txtdata.setText(buffer.toString());
                            }
                        },
                        new Response.ErrorListener() {
                            @Override
                            public void onErrorResponse(VolleyError error) {
                                error.printStackTrace();
                            }
                        }
                );
                queue.add(jsonArrayRequest);
            }
        });
    }
}

okhttp

build.gradle.kts:
    implementation("com.squareup.okhttp3:okhttp:4.12.0")

AndroidManifest.xml:
    <uses-permission android:name="android.permission.INTERNET"/>

MainActivity.java:
package com.example.okhttp;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import okhttp3.Call;
import okhttp3.Callback;
import okhttp3.OkHttp;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class MainActivity extends AppCompatActivity {

    Button btnString, btnJson;
    TextView txtdata;
    String links = "https://www.w3schools.com/xml/note.xml";
    String Jsonlinks = "https://mocki.io/v1/7d6d5cdb-04bf-4df6-8e0c-5e0a70069eb4";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        txtdata = findViewById(R.id.textView);
        btnString = findViewById(R.id.btnString);
        btnJson = findViewById(R.id.btnJson);
        OkHttpClient client = new OkHttpClient();

        btnString.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Request req = new Request.Builder().url(links).build();
                client.newCall(req).enqueue(new Callback() {
                    @Override
                    public void onFailure(@NonNull Call call, @NonNull IOException e) {
                        e.printStackTrace();
                    }

                    @Override
                    public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
                        txtdata.setText(response.body().string());
                    }
                });
            }
        });

        btnJson.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Request jsonReq = new Request.Builder().url(Jsonlinks).build();

                client.newCall(jsonReq).enqueue(new Callback() {
                    @Override
                    public void onFailure(@NonNull Call call, @NonNull IOException e) {
                        e.printStackTrace();
                    }

                    @Override
                    public void onResponse(@NonNull Call call, @NonNull Response response) throws IOException {
                        try {
                            String jsonString = response.body().string();
                            JSONArray jsonArray = new JSONArray(jsonString);
                            StringBuffer buffer = new StringBuffer();
                            for (int i = 0; i < jsonArray.length(); i++) {
                                JSONObject studentObj = jsonArray.getJSONObject(i);
                                buffer.append("Roll no.: " + studentObj.getInt("roll") + "\n" +
                                        "Name: " + studentObj.getString("name") + "\n" +
                                        "Email: " + studentObj.getString("email") + "\n\n");
                            }
                            MainActivity.this.runOnUiThread(() -> {
                                txtdata.setText(buffer.toString());
                            });
                        } catch (JSONException e) {
                            e.printStackTrace();
                            MainActivity.this.runOnUiThread(() -> {
                                txtdata.setText(e.getMessage());
                            });
                        }
                    }

                });
            }
        });
    }
}

-> res → layout → activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:padding="20dp"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/btnString"
        android:text="Fetch XML"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/btnJson"
        android:text="Fetch JSON"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="12dp" />

    <TextView
        android:id="@+id/textView"
        android:text=""
        android:textSize="16sp"
        android:padding="16dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

retrofit

MainActivity.java
package com.example.myapplication;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import java.util.List;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        TextView txtview;
        Button btnfetch;
        String url= "https://jsonplaceholder.typicode.com/";
        txtview=findViewById(R.id.txtview);
        btnfetch=findViewById(R.id.btnfetch);

        btnfetch.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Retrofit retrofit=new Retrofit.Builder()
                        .baseUrl(url)
                        .addConverterFactory(GsonConverterFactory.create())
                        .build();

                myapi api=retrofit.create(myapi.class);
                Call<List<model>> call=api.getmodels();
                call.enqueue(new Callback<List<model>>() {
                    @Override
                    public void onResponse(Call<List<model>> call, Response<List<model>> response) {
                        List<model> data=response.body();
                        for(int i=0;i<data.size();i++){
                            txtview.append("id:"+ data.get(i).getId()+ "\n");
                            txtview.append("user_id: "+data.get(i).getUserId()+"\n");
                            txtview.append("Title: "+data.get(i).getTitle()+"\n");
                            txtview.append("Body: "+data.get(i).getBody()+"\n\n");
                        }
                    }

                    @Override
                    public void onFailure(Call<List<model>> call, Throwable t) {

                    }
                });
            }
        });
    }
}

myapi.java
package com.example.myapplication;

import java.util.List;
import retrofit2.Call;
import retrofit2.http.GET;

public interface myapi {
    @GET("posts")
    Call <List<model>> getmodels ();
}

model.java
package com.example.myapplication;

public class model {
    int userId,id;
    String title,body;

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getBody() {
        return body;
    }

    public void setBody(String body) {
        this.body = body;
    }
}

activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:padding="16dp"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:id="@+id/btnfetch"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Fetch Posts" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginTop="12dp">

        <TextView
            android:id="@+id/txtview"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textSize="14sp"
            android:padding="8dp" />
    </ScrollView>

</LinearLayout>

crud sqlite

MainActivity.java
package com.example.myapplication;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
import android.annotation.SuppressLint;
import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import android.app.DatePickerDialog;
import java.time.LocalDate;
import java.time.Period;
import java.time.format.DateTimeFormatter;
import java.util.Calendar;

public class MainActivity extends AppCompatActivity {
    private EditText edtname, edtrno, edtDob, edtstream, edtAddress;
    private Button btninsert, btnread, btndelete, btnsearch, btnupdate;
    private TextView txtdata;
    private dbhandler con;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initializeViews();
        
        con = new dbhandler(this);
        con.getWritableDatabase();

        setupButtonListeners();
    }

    private void initializeViews() {
        btninsert = findViewById(R.id.btninsert);
        btnread = findViewById(R.id.btnread);
        btndelete = findViewById(R.id.btndelete);
        btnsearch = findViewById(R.id.btnsearch);
        btnupdate = findViewById(R.id.btnupdate);
        txtdata = findViewById(R.id.txtdata);
        edtname = findViewById(R.id.edtname);
        edtrno = findViewById(R.id.edtrno);
        edtDob = findViewById(R.id.edtDob);
        edtstream = findViewById(R.id.edtstream);
        edtAddress = findViewById(R.id.edtAddress);
    }

    private void setupButtonListeners() {
        btninsert.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = edtname.getText().toString();
                int rno = Integer.parseInt(edtrno.getText().toString());
                String dob = edtDob.getText().toString();
                String stream = edtstream.getText().toString();
                String address = edtAddress.getText().toString();
                
                boolean status = con.savedata(name, rno, dob, stream, address);
                Toast.makeText(
                    getApplicationContext(), 
                    status ? "Inserted successfully" : "Insertion failed", 
                    Toast.LENGTH_LONG
                ).show();
            }
        });

        btnread.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Cursor c = con.showdata();
                StringBuffer buffer = new StringBuffer();
                
                if (c.getCount() == 0) {
                    Toast.makeText(
                        getApplicationContext(), 
                        "No record Found", 
                        Toast.LENGTH_LONG
                    ).show();
                    return;
                }

                while (c.moveToNext()) {
                    buffer.append("ID:" + c.getString(0) + "\n");
                    buffer.append("ROLL Number " + c.getInt(1) + "\n");
                    buffer.append("Student name: " + c.getString(2) + "\n");
                    
                    String dobStr = c.getString(3);
                    buffer.append("Date of Birth: " + dobStr + "\n");
                    
                    try {
                        int age = calculateAge(dobStr);
                        buffer.append("Age: " + age + "\n");
                    } catch (Exception e) {
                        buffer.append("Age: N/A\n");
                    }
                    
                    buffer.append("Stream: " + c.getString(4) + "\n");
                    buffer.append("Address: " + c.getString(5) + "\n\n");
                }
                
                showmessage("Records", buffer.toString());
            }
        });

        btndelete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = edtname.getText().toString();
                int status = con.deleterecord(name);
                
                Toast.makeText(
                    getApplicationContext(), 
                    status > 0 ? "Deleted successfully" : "Deletion failed", 
                    Toast.LENGTH_LONG
                ).show();
            }
        });

        btnupdate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String name = edtname.getText().toString();
                int rno = Integer.parseInt(edtrno.getText().toString());
                
                int status = con.updaterecord(name, rno);
                Toast.makeText(
                    getApplicationContext(), 
                    status == -1 ? "Updated unsuccessfully" : "Updated successfully", 
                    Toast.LENGTH_LONG
                ).show();
            }
        });

        btnsearch.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Integer rno = Integer.parseInt(edtrno.getText().toString());
                StringBuffer buffer = new StringBuffer();
                Cursor c = con.searchdata(rno);
                
                if (c.getCount() == 0) {
                    Toast.makeText(
                        getApplicationContext(), 
                        "No record Found", 
                        Toast.LENGTH_LONG
                    ).show();
                    showmessage("records", "no record found");
                    return;
                }

                while (c.moveToNext()) {
                    buffer.append("ID: " + c.getString(0) + "\n");
                    buffer.append("ROLL Number: " + c.getInt(1) + "\n");
                    buffer.append("Student name: " + c.getString(2) + "\n");
                    
                    String dobStr = c.getString(3);
                    buffer.append("Date of Birth: " + dobStr + "\n");
                    
                    try {
                        int age = calculateAge(dobStr);
                        buffer.append("Age: " + age + "\n");
                    } catch (Exception e) {
                        buffer.append("Age: N/A\n");
                    }
                    
                    buffer.append("Stream: " + c.getString(4) + "\n");
                    buffer.append("Address: " + c.getString(5) + "\n\n");
                }
                
                txtdata.setText(buffer.toString());
            }
        });

        edtDob.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                final Calendar c = Calendar.getInstance();
                int year = c.get(Calendar.YEAR);
                int month = c.get(Calendar.MONTH);
                int day = c.get(Calendar.DAY_OF_MONTH);
                
                DatePickerDialog datePickerDialog = new DatePickerDialog(
                    MainActivity.this,
                    new DatePickerDialog.OnDateSetListener() {
                        @Override
                        public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
                            edtDob.setText(dayOfMonth + "/" + (monthOfYear + 1) + "/" + year);
                        }
                    },
                    year, month, day
                );
                
                datePickerDialog.show();
            }
        });
    }

    private void showmessage(String title, String Message) {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setCancelable(true);
        builder.setTitle(title);
        builder.setMessage(Message);
        builder.show();
    }

    private int calculateAge(String dobStr) {
        try {
            @SuppressLint("SimpleDateFormat")
            java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat("dd/MM/yyyy");
            java.util.Date dobDate = sdf.parse(dobStr);
            
            Calendar dob = Calendar.getInstance();
            dob.setTime(dobDate);
            Calendar today = Calendar.getInstance();
            
            int age = today.get(Calendar.YEAR) - dob.get(Calendar.YEAR);
            
            if (today.get(Calendar.MONTH) < dob.get(Calendar.MONTH) ||
                (today.get(Calendar.MONTH) == dob.get(Calendar.MONTH) &&
                 today.get(Calendar.DAY_OF_MONTH) < dob.get(Calendar.DAY_OF_MONTH))) {
                age--;
            }
            
            return age;
        } catch (Exception e) {
            e.printStackTrace();
            return -1;
        }
    }
}

DBHandler.java:
package com.example.myapplication;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHandler extends SQLiteOpenHelper {
    
    private static final String DB_NAME = "student.db";
    private static final String TABLE_NAME = "student";
    private static final int DB_VERSION = 7;

    public DatabaseHandler(Context context) {
        super(context, DB_NAME, null, DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String query = "CREATE TABLE " + TABLE_NAME +
                " (" +
                    "ID INTEGER PRIMARY KEY AUTOINCREMENT," +
                    "RNO INTEGER," +
                    "NAME TEXT," +
                    "DOB TEXT," +
                    "STREAM TEXT," +
                    "ADDRESS TEXT" +
                ")";
        
        db.execSQL(query);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        if (oldVersion < 4) {
            db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
            onCreate(db);
        }
    }

    public boolean saveData(String name, int rno, String dob, String stream, String address) {
        try {
            SQLiteDatabase db = getWritableDatabase();
            ContentValues contentValues = new ContentValues();

            contentValues.put("RNO", rno);
            contentValues.put("NAME", name);
            contentValues.put("DOB", dob);
            contentValues.put("STREAM", stream);
            contentValues.put("ADDRESS", address);

            long status = db.insert(TABLE_NAME, null, contentValues);
            return status != -1;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

    public Cursor showData() {
        String query = "SELECT * FROM " + TABLE_NAME;
        SQLiteDatabase db = this.getReadableDatabase();
        return db.rawQuery(query, null);
    }

    public int deleteRecord(String name) {
        SQLiteDatabase db = this.getWritableDatabase();
        return db.delete(TABLE_NAME, "NAME=?", new String[] { name });
    }

    public int updateRecord(String name, int rno) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();

        contentValues.put("RNO", rno);
        contentValues.put("NAME", name);

        return db.update(TABLE_NAME, contentValues, "RNO=" + rno, null);
    }

    public Cursor searchData(int rno) {
        String query = "SELECT * FROM " + TABLE_NAME + " WHERE RNO=?";
        SQLiteDatabase db = this.getReadableDatabase();
        
        return db.rawQuery(query, new String[] { String.valueOf(rno) });
    }
}

crud firebase

Select Hamburger > Tools > Firebase > Realtime Database Java > Follow the instructions by connecting and creating things

Student.java
package com.example.firebase;
public class Student {
 String id;
 Integer rollno;
 String name;
 Double gradePointAverage;
 String department;

 public Student(String id, Integer rollno, String name, Double gradePointAverage, String department) {
 this.id = id;
 this.rollno = rollno;
 this.name = name;
 this.gradePointAverage = gradePointAverage;
 this.department = department;
 }

 public Student() {}

 public String getId() {
 return id;
 }

 public void setId(String id) {
 this.id = id;
 }

 public Integer getRollno() {
 return rollno;
 }

 public void setRollno(Integer rollno) {
 this.rollno = rollno;
 }

 public String getName() {
 return name;
 }

 public void setName(String name) {
 this.name = name;
 }

 public Double getGradePointAverage() {
 return gradePointAverage;
 }

 public void setGradePointAverage(Double gradePointAverage) {
 this.gradePointAverage = gradePointAverage;
 }

 public String getDepartment() {
 return department;
 }

 public void setDepartment(String department) {
 this.department = department;
 }
}

Activity_xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent">

 <LinearLayout
 android:padding="16dp"
 android:orientation="vertical"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:fitsSystemWindows="true">

 <EditText
 android:id="@+id/edname"
 android:hint="Name"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"/>

 <EditText
 android:id="@+id/edrollno"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:hint="Roll No"
 android:inputType="numberDecimal" />

 <EditText
 android:id="@+id/edgpa"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:hint="GPA"
 android:inputType="numberDecimal" />

 <EditText
 android:id="@+id/eddept"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:hint="Department" />

 <Button
 android:id="@+id/btnadd"
 android:text="Add User"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"/>

 <Button
 android:id="@+id/btnupdate"
 android:text="Update User"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"/>

 <Button
 android:id="@+id/btndel"
 android:text="Delete User"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"/>

 <Button
 android:id="@+id/btnview"
 android:text="View All Users"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"/>

 <ListView
 android:id="@+id/lv"
 android:layout_width="match_parent"
 android:layout_height="0dp"
 android:layout_weight="1"/>
 </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.java
package com.example.firebase;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

 EditText edname, edrollno, edgpa, eddept;
 Button btnadd, btnview, btndel, btnupdate;
 ListView lv;
 String selectedId = "";

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);

 edname = findViewById(R.id.edname);
 edrollno = findViewById(R.id.edrollno);
 edgpa = findViewById(R.id.edgpa);
 eddept = findViewById(R.id.eddept);

 btnadd = findViewById(R.id.btnadd);
 btnview = findViewById(R.id.btnview);
 btnupdate = findViewById(R.id.btnupdate);
 btndel = findViewById(R.id.btndel);
 lv = findViewById(R.id.lv);

 List<Student> studentList = new ArrayList<>();

 FirebaseDatabase database = FirebaseDatabase.getInstance();
 DatabaseReference myRef = database.getReference("student");

 btnadd.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 String name = edname.getText().toString();
 Integer roll = Integer.parseInt(edrollno.getText().toString());
 Double gpa = Double.parseDouble(edgpa.getText().toString());
 String dept = eddept.getText().toString();

 selectedId = myRef.push().getKey();
 myRef.child(selectedId).setValue(new Student(selectedId, roll, name, gpa, dept));
 Toast.makeText(getApplicationContext(),"Data inserted successfully!!!",Toast.LENGTH_LONG).show();
 }
 });

 btndel.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 if (!selectedId.isEmpty()){
 myRef.child(selectedId).removeValue();
 Toast.makeText(getApplicationContext(),"Data deleted successfully!!!",Toast.LENGTH_LONG).show();
 }
 else{
 Toast.makeText(getApplicationContext(),"Error in deletion!!!",Toast.LENGTH_LONG).show();
 }
 }
 });

 btnupdate.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 if (!selectedId.isEmpty()) {
 String name = edname.getText().toString();
 int rollno = Integer.parseInt(edrollno.getText().toString());
 Double gpa = Double.parseDouble(edgpa.getText().toString());
 String dept = eddept.getText().toString();

 myRef.child(selectedId).setValue(new Student(selectedId, rollno, name, gpa, dept));
 Toast.makeText(MainActivity.this, "Data updated successfully!", Toast.LENGTH_SHORT).show();
 } else {
 Toast.makeText(MainActivity.this, "Select a student to update!", Toast.LENGTH_SHORT).show();
 }
 }
 });

 lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
 @Override
 public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
 Student s = studentList.get(position);
 edname.setText(s.getName());
 edrollno.setText(String.valueOf(s.getRollno()));
 edgpa.setText(String.valueOf(s.getGradePointAverage()));
 eddept.setText(s.getDepartment());
 selectedId = s.getId();
 }
 });

 btnview.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
 myRef.addListenerForSingleValueEvent(new ValueEventListener() {
 @Override
 public void onDataChange(@NonNull DataSnapshot snapshot) {
 studentList.clear();
 for(DataSnapshot snp : snapshot.getChildren()) {
 Student std = snp.getValue(Student.class);
 studentList.add(std);
 }

 List<String> display = new ArrayList<>();
 for(Student s: studentList) {
 display.add("ID: " + s.getId() +
 "\nRoll No: " + s.getRollno() +
 "\nName: " + s.getName() +
 "\nGPA: " + s.getGradePointAverage() +
 "\nDepartment: " + s.getDepartment());
 }
 ArrayAdapter<String> adapter = new ArrayAdapter<>(MainActivity.this,
 android.R.layout.simple_list_item_1, display);
 lv.setAdapter(adapter);
 }

 @Override
 public void onCancelled(@NonNull DatabaseError error) {
 }
 });
 }
 });
 }
}

Shared Pref

SplashScreen.java
package com.example.myapplication;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.os.Handler;
import androidx.appcompat.app.AppCompatActivity;

public class SplashActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash);
        SharedPreferences prefs = getSharedPreferences("MyPrefs", MODE_PRIVATE);
        final boolean loggedIn = prefs.getBoolean("isLoggedIn", false);
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                if (loggedIn) {
                    startActivity(new Intent(SplashActivity.this, HomeActivity.class));
                } else {
                    startActivity(new Intent(SplashActivity.this, LoginActivity.class));
                }
                finish();
            }
        }, 1500);
    }
}

LoginActivity.java
package com.example.myapplication;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class LoginActivity extends AppCompatActivity {

    EditText etUser, etPass;
    CheckBox chkRemember;
    Button btnLogin;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        etUser = findViewById(R.id.etUser);
        etPass = findViewById(R.id.etPass);
        chkRemember = findViewById(R.id.chkRemember);
        btnLogin = findViewById(R.id.btnLogin);

        btnLogin.setOnClickListener(v -> {
            String username = etUser.getText().toString().trim();
            String password = etPass.getText().toString().trim();

            if (username.equals("admin") && password.equals("1234")) {
                if (chkRemember.isChecked()) {
                    SharedPreferences prefs = getSharedPreferences("MyPrefs", MODE_PRIVATE);
                    SharedPreferences.Editor editor = prefs.edit();
                    editor.putBoolean("isLoggedIn", true);
                    editor.apply();
                }

                startActivity(new Intent(LoginActivity.this, HomeActivity.class));
                finish();
            } else {
                Toast.makeText(LoginActivity.this, "Invalid Username or Password", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

HomeActivity.java
package com.example.myapplication;
import android.content.Intent;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.widget.Button;
import androidx.appcompat.app.AppCompatActivity;

public class HomeActivity extends AppCompatActivity {

    Button btnLogout;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        btnLogout = findViewById(R.id.btnLogout);

        btnLogout.setOnClickListener(v -> {
            SharedPreferences prefs = getSharedPreferences("MyPrefs", MODE_PRIVATE);
            SharedPreferences.Editor editor = prefs.edit();
            editor.clear();
            editor.apply();

            startActivity(new Intent(HomeActivity.this, LoginActivity.class));
            finish();
        });
    }
}

Alert-SP

MainActivity.java
package com.example.myapplication;
import android.content.DialogInterface;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    EditText etUser, etPass;
    Button btnLogin;
    SharedPreferences prefs;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        etUser = findViewById(R.id.etUser);
        etPass = findViewById(R.id.etPass);
        btnLogin = findViewById(R.id.btnLogin);
        prefs = getSharedPreferences("MyPrefs", MODE_PRIVATE);
        etUser.setText(prefs.getString("username", ""));
        etPass.setText(prefs.getString("password", ""));
        btnLogin.setOnClickListener(v -> showAlert());
    }

    private void showAlert() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Save Login?");
        builder.setMessage("Do you want to save your credentials?");

        builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                SharedPreferences.Editor editor = prefs.edit();
                editor.putString("username", etUser.getText().toString());
                editor.putString("password", etPass.getText().toString());
                editor.apply();
                Toast.makeText(MainActivity.this, "Saved!", Toast.LENGTH_SHORT).show();
            }
        });

        builder.setNegativeButton("No", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                Toast.makeText(MainActivity.this, "Not Saved", Toast.LENGTH_SHORT).show();
            }
        });

        builder.show();
    }
}

notification

MainActivity.java
package com.example.myapplication;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;
import androidx.core.app.NotificationCompat;
import androidx.core.content.ContextCompat;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button btn = findViewById(R.id.btnNotify);

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(
                    "myChannel",
                    "MyChannel",
                    NotificationManager.IMPORTANCE_DEFAULT
            );
            NotificationManager manager = getSystemService(NotificationManager.class);
            if (manager != null) {
                manager.createNotificationChannel(channel);
            }
        }

        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
            if (ContextCompat.checkSelfPermission(this,
                    android.Manifest.permission.POST_NOTIFICATIONS) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(this,
                        new String[]{android.Manifest.permission.POST_NOTIFICATIONS}, 100);
            }
        }

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(MainActivity.this, SecondActivity.class);
                intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);

                PendingIntent pi = PendingIntent.getActivity(
                        MainActivity.this,
                        0,
                        intent,
                        PendingIntent.FLAG_UPDATE_CURRENT | PendingIntent.FLAG_IMMUTABLE
                );

                NotificationCompat.Builder builder = new NotificationCompat.Builder(MainActivity.this, "myChannel")
                        .setSmallIcon(android.R.drawable.ic_dialog_info)
                        .setContentTitle("Simple Notification")
                        .setContentText("Tap to open SecondActivity")
                        .setPriority(NotificationCompat.PRIORITY_DEFAULT)
                        .setContentIntent(pi)
                        .setAutoCancel(true);

                NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
                if (manager != null) {
                    manager.notify(1, builder.build());
                }
            }
        });
    }
}
SecondActivity.java
package com.example.myapplication;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;

public class SecondActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_second);
    }
}

AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.MyApplication">
        <activity
            android:name=".SecondActivity"
            android:exported="false" />
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>