write an application to demonstrate Alert Dialog Box in android

 activity.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:app="http://schemas.android.com/apk/res-auto"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity">

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginTop="180dp"

        android:gravity="center_horizontal"

        android:text="Press The Back Button of Your Phone."

        android:textSize="30dp"

        android:textStyle="bold" />

</RelativeLayout>

activity.java

import androidx.appcompat.app.AppCompatActivity;

import androidx.appcompat.app.AlertDialog;

import androidx.appcompat.app.AppCompatActivity;

import android.content.DialogInterface;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

    }

    @Override

    public void onBackPressed() {

        // Create the object of AlertDialog Builder class

        AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);

        // Set the message show for the Alert time

        builder.setMessage("Do you want to exit ?");

        // Set Alert Title

        builder.setTitle("Alert !");

        // Set Cancelable false for when the user clicks on the outside the Dialog Box then it will remain show

        builder.setCancelable(false);

        // Set the positive button with yes name Lambda OnClickListener method is use of DialogInterface interface.

        builder.setPositiveButton("Yes", (DialogInterface.OnClickListener) (dialog, which) -> {

            // When the user click yes button then app will close

            finish();

        });

        // Set the Negative button with No name Lambda OnClickListener method is use of DialogInterface interface.

        builder.setNegativeButton("No", (DialogInterface.OnClickListener) (dialog, which) -> {

            // If user click no then dialog box is canceled.

            dialog.cancel();

        });

        // Create the Alert dialog

        AlertDialog alertDialog = builder.create();

        // Show the Alert Dialog box

        alertDialog.show();

    }

}