Android studio Exit button

 Java file.........

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {

    final Context context = this;
    private Button button;

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button) findViewById(R.id.buttonAlert);

        // add button listener
        button.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View arg0) {

                    AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
                        context);

                    // set title
                    alertDialogBuilder.setTitle("Your Title");

                    // set dialog message
                    alertDialogBuilder
                        .setMessage("Click yes to exit!")
                        .setCancelable(false)
                        .setPositiveButton("Yes",new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,int id) {
                                // if this button is clicked, close
                                // current activity
                                MainActivity.this.finish();
                            }
                        })
                        .setNegativeButton("No",new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog,int id) {
                                // if this button is clicked, just close
                                // the dialog box and do nothing
                                dialog.cancel();
                            }
                        });

                    // create alert dialog
                    AlertDialog alertDialog = alertDialogBuilder.create();

                    // show it
                    alertDialog.show();
                }
            });
    }
}

  



XML code
    <Button
        android:id="@+id/buttonAlert"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Show Alert Box" />