Addition of two numbers in android

Mainactivity.java

public class MainActivity extends AppCompatActivity implements View.OnClickListener{

private EditText editText,editText2,editText4;

    int v1,v2,v3;

    String s="ans";
private Button button;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


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

        button.setOnClickListener(this);

    }
    @Override
    public void onClick(View v)
    {
        editText=(EditText)findViewById(R.id.editText);

        editText2=(EditText)findViewById(R.id.editText2);

        editText4=(EditText)findViewById(R.id.editText4);

         v1=Integer.parseInt(editText.getText().toString());

         v2=Integer.parseInt(editText2.getText().toString());

         v3=v1+v2;

    

         s=String.valueOf(v3);

        editText4.setText(s);
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    } 
activitymain.xml
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <EditText
        android:layout_width="500dp"
        android:layout_height="40dp"
        android:id="@+id/editText2"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="60dp" />

    <EditText
        android:layout_width="500dp"
        android:layout_height="40dp"
        android:id="@+id/editText"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_below="@+id/editText2" />
    <EditText
        android:layout_width="800dp"
        android:layout_height="40dp"
        android:id="@+id/editText4"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_below="@+id/editText" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="OK"
        android:id="@+id/button"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true" />


</RelativeLayout>