Tost Message on button click

java file
package com.example.viraj.blog_4_tostmessage;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button B1=(Button)findViewById(R.id.id_button);
        B1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this,"TOST IS WORKING",Toast.LENGTH_LONG).show();
            }
        });
    }
}

xml file

<?xml version="1.0" encoding="utf-8"?>

<android.support.constraint.ConstraintLayout 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="com.example.viraj.blog_4_tostmessage.MainActivity">

    <Button

        android:id="@+id/id_button"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_marginBottom="8dp"

        android:layout_marginLeft="8dp"

        android:layout_marginRight="8dp"

        android:layout_marginTop="8dp"

        android:text="CLICK TO DISPLAY TOST MESAGE"

        app:layout_constraintBottom_toBottomOf="parent"

        app:layout_constraintLeft_toLeftOf="parent"

        app:layout_constraintRight_toRightOf="parent"

        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>