java file of calulator

package com.example.user.shishu;

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

public class MainActivity extends AppCompatActivity {
    int a, b;
    Button one, two, three, four, five, six, seven, eight, nine, zero, add, sub, mul, div, equal, clear;
    EditText disp;
    Character opr;


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


        one = (Button) findViewById(R.id.b1);
        two = (Button) findViewById(R.id.b2);
        three = (Button) findViewById(R.id.b3);
        four = (Button) findViewById(R.id.b5);
        five = (Button) findViewById(R.id.b6);
        six = (Button) findViewById(R.id.b7);
        seven = (Button) findViewById(R.id.b9);
        eight = (Button) findViewById(R.id.b10);
        nine = (Button) findViewById(R.id.b11);
        zero = (Button) findViewById(R.id.b13);
        clear = (Button) findViewById(R.id.b14);
        equal = (Button) findViewById(R.id.b15);
        div = (Button) findViewById(R.id.b16);
        add = (Button) findViewById(R.id.b4);
        sub = (Button) findViewById(R.id.b8);
        mul = (Button) findViewById(R.id.b12);
        disp = (EditText) findViewById(R.id.e1);


        one.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("1");
            }
        });

        two.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("2");
            }
        });

        three.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("3");
            }
        });


        four.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("4");
            }
        });

        five.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("5");
            }
        });

        six.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("6");
            }
        });


        seven.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("7");
            }
        });


        eight.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("8");
            }
        });

        nine.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("9");
            }
        });


        zero.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("0");
            }
        });


        add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                a = Integer.parseInt(disp.getText().toString());
                opr = '+';
                disp.setText("");


            }
        });

        sub.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                a = Integer.parseInt(disp.getText().toString());
                opr = '-';
                disp.setText("");


            }
        });

        mul.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                a = Integer.parseInt(disp.getText().toString());
                opr = '*';
                disp.setText("");


            }
        });

        div.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                a = Integer.parseInt(disp.getText().toString());
                opr = '/';
                disp.setText("");


            }
        });

        equal.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                b = Integer.parseInt(disp.getText().toString());
                if (opr == '+') ;
                int sum = a + b;
                Toast.makeText(getApplicationContext(), String.valueOf(sum), Toast.LENGTH_LONG).show();

            }
        });

        clear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                disp.setText("");
            }
        });


    }


}