main activity

MainActivity.java

package com.wotinstitutes.greetings;

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

public class MainActivity extends AppCompatActivity {

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

       Button btn=(Button)findViewById(R.id.button2);
       btn.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
               Intent intent=new Intent(MainActivity.this,Main2Activity.class);
               int b=sum(20,80);
               intent.putExtra("a",b);
               startActivity(intent);
           }
       });
    }

    public int sum(int x,int y){
        int a=x;
        int b=y;
        int z=a+b;
        return z;
    }
}