Game2.java

package com.application.brainfit;

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

public class Game2 extends AppCompatActivity {
Button easy, medium, hard, expert;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_game2);
        easy = (Button) findViewById(R.id.easy);
        medium = (Button) findViewById(R.id.medium);
        hard = (Button) findViewById(R.id.hard);
        expert = (Button) findViewById(R.id.expert);

        easy.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent(getApplicationContext(), G2Easy.class);
                startActivity(i);
                finish();
            }
        });

        medium.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent(getApplicationContext(), G2Medium.class);
                startActivity(i);
                finish();
            }
        });

        hard.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent(getApplicationContext(), G2Hard.class);
                startActivity(i);
                finish();
            }
        });

        expert.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent i = new Intent(getApplicationContext(), G2Expert.class);
                startActivity(i);
                finish();
            }
        });
    }
}