MainActivity.java

package com.lenovo.alertdemo;

import android.content.DialogInterface;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

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

        new AlertDialog.Builder(this)
                .setIcon(android.R.drawable.ic_dialog_alert)
                .setTitle("Are you Sure")
                .setMessage("Do you definelty want to do this!!")
                .setPositiveButton("Yes",new DialogInterface.OnClickListener(){

                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        Toast.makeText(MainActivity.this,"It's Done",Toast.LENGTH_SHORT).show();

                    }
                })
                .setNegativeButton("No",null)
                .show();
    }
}