simple interest calculations

import android.widget.*;

import android.view.*;

import android.view.View.OnClickListener;

public class MainActivity extends Activity {

Button b1;

EditText t1,t2,t3,t4;

      @Override

      protected void onCreate(Bundle savedInstanceState) {

                  super.onCreate(savedInstanceState);

                  setContentView(R.layout.activity_main);

                  t1=(EditText) findViewById(R.id.editText1);

                  t2=(EditText) findViewById(R.id.editText2);

                  t3=(EditText) findViewById(R.id.editText3);

                  t4=(EditText) findViewById(R.id.editText4);

                  b1=(Button) findViewById(R.id.button1);

                  b1.setOnClickListener(s1);

      }

      public OnClickListener s1=new OnClickListener()

      {

         public void onClick(View v){

                     if(v==b1){

                     float p=Float.parseFloat(t1.getText().toString());

                     float n=Float.parseFloat(t2.getText().toString());

                     float r=Float.parseFloat(t3.getText().toString());

                     float si=p*n*r/100;

                     t4.setText(String.valueOf(si));

                    }

         }};}