calculator.java package com.inti.student.calculator;

import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.view.View; import android.webkit.WebView; import android.widget.Button; import android.widget.EditText; import android.widget.TextView; import android.widget.Toast;

public class calculator extends AppCompatActivity {

Button sum, subtract, multiply, divide, remainder, clear;
TextView answer;
EditText num1, num2;
private int no1, no2, result;
private double a, b, resultD;

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

    //Finding views
    sum = findViewById(R.id.sum);
    subtract = findViewById(R.id.subtract);
    multiply = findViewById(R.id.multiply);
    divide = findViewById(R.id.divide);
    remainder = findViewById(R.id.remainder);
    clear = findViewById(R.id.clear);

    num1 = findViewById(R.id.num1);
    num2 = findViewById(R.id.num2);

    answer = findViewById(R.id.answer);


    sum.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Add();
        }
    });

    subtract.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Sub();
        }
    });

    multiply.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Mult();
        }
    });

    divide.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Div();
        }
    });

    remainder.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Rem();
        }
    });

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


}

 private void Add() {
    if (num1.getText().toString().length() !=0 && num2.getText().toString().length() !=0) {
         if (num1.getText().toString().contains(".") || num2.getText().toString().contains(".")) {
            a = Double.parseDouble(num1.getText().toString());
            b = Double.parseDouble(num2.getText().toString());
            resultD = a + b;
            answer.setText(String.valueOf(resultD));
        } else {
            no1 = Integer.parseInt(num1.getText().toString());
            no2 = Integer.parseInt(num2.getText().toString());
            result = no1 + no2;
            answer.setText(String.valueOf(result));
        }
    } else {
        Toast errorToast = Toast.makeText(calculator.this, "Please make sure all column is filled up!!!", Toast.LENGTH_SHORT);
        errorToast.show();
    }
}


private void Sub() {
    if (num1.getText().toString().length() !=0 && num2.getText().toString().length() !=0) {
         if (num1.getText().toString().contains(".") || num2.getText().toString().contains(".")) {
            a = Double.parseDouble(num1.getText().toString());
            b = Double.parseDouble(num2.getText().toString());
            resultD = a - b;
            answer.setText(String.valueOf(resultD));
        } else {
            no1 = Integer.parseInt(num1.getText().toString());
            no2 = Integer.parseInt(num2.getText().toString());
            result = no1 - no2;
            answer.setText(String.valueOf(result));
        }
    } else {
        Toast errorToast = Toast.makeText(calculator.this, "Please make sure all column is filled up!!!", Toast.LENGTH_SHORT);
        errorToast.show();
    }
}


private void Mult() {
    if (num1.getText().toString().length() !=0 && num2.getText().toString().length() !=0) {
        if (num1.getText().toString().contains(".") || num2.getText().toString().contains(".")) {
            a = Double.parseDouble(num1.getText().toString());
            b = Double.parseDouble(num2.getText().toString());
            resultD = a * b;
            answer.setText(String.valueOf(resultD));
        } else {
            no1 = Integer.parseInt(num1.getText().toString());
            no2 = Integer.parseInt(num2.getText().toString());
            result = no1 * no2;
            answer.setText(String.valueOf(result));
        }
    } else {
        Toast errorToast = Toast.makeText(calculator.this, "Please make sure all column is filled up!!!", Toast.LENGTH_SHORT);
        errorToast.show();
    }
}

private void Div() {
    if (num1.getText().toString().length() !=0 && num2.getText().toString().length() !=0) {
        if (num1.getText().toString().contains(".") || num2.getText().toString().contains(".")) {
            a = Double.parseDouble(num1.getText().toString());
            b = Double.parseDouble(num2.getText().toString());
            resultD = a / b;
            answer.setText(String.valueOf(resultD));
        } else {
            no1 = Integer.parseInt(num1.getText().toString());
            no2 = Integer.parseInt(num2.getText().toString());
            result = no1 / no2;
            answer.setText(String.valueOf(result));
        }
    } else {
        Toast errorToast = Toast.makeText(calculator.this, "Please make sure all column is filled up!!!", Toast.LENGTH_SHORT);
        errorToast.show();
    }
}

private void Rem() {
    if (num1.getText().toString().length() !=0 && num2.getText().toString().length() !=0) {
        if (num1.getText().toString().contains(".") || num2.getText().toString().contains(".")) {
            a = Double.parseDouble(num1.getText().toString());
            b = Double.parseDouble(num2.getText().toString());
            resultD = a % b;
            answer.setText(String.valueOf(resultD));
        } else {
            no1 = Integer.parseInt(num1.getText().toString());
            no2 = Integer.parseInt(num2.getText().toString());
            result = no1 % no2;
            answer.setText(String.valueOf(result));
        }
    } else {
        Toast errorToast = Toast.makeText(calculator.this, "Please make sure all column is filled up!!!", Toast.LENGTH_SHORT);
        errorToast.show();
    }
}

public void Clr() {
    if (num1.getText().toString().length() >= 1 && num2.getText().toString().length() >= 1) {
        num1.setText("");
        num2.setText("");
        answer.setText("");

    }
}

} activity_calculator.xml

<EditText
    android:id="@+id/num1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="10dp"
    android:ems="10"
    android:hint="Number1"
    android:inputType="number|numberDecimal|numberSigned"/>

<EditText
    android:id="@+id/num2"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="62dp"
    android:ems="10"
    android:hint="Number2"
    android:inputType="number|numberDecimal|numberSigned"/>

<!--Created By Ashim -->

<Button
    android:id="@+id/sum"
    android:layout_width="353dp"
    android:layout_height="wrap_content"
    android:layout_above="@+id/subtract"
    android:layout_marginBottom="0dp"
    android:text="Sum +"
    android:textSize="25sp"/>

<Button
    android:id="@+id/subtract"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_marginBottom="160dp"
    android:text="Subtract -"
    android:textSize="25sp"/>

<Button
    android:id="@+id/multiply"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@+id/subtract"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="-160dp"
    android:text="Multiply x"
    android:textSize="25sp"/>

<Button
    android:id="@+id/remainder"
    android:layout_width="354dp"
    android:layout_height="53dp"
    android:layout_below="@+id/divide"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="-7dp"
    android:text="Remainder %"
    android:textSize="25sp"/>

<Button
    android:id="@+id/divide"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@+id/multiply"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="7dp"
    android:text="Divide /"
    android:textSize="25sp"/>

<Button
    android:id="@+id/clear"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/answer"
    android:layout_marginTop="-313dp"
    android:layout_marginEnd="34dp"
    android:layout_marginRight="34dp"
    android:text="Clear"/>

<TextView
    android:id="@+id/answer"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="313dp"
    android:textSize="30sp"/>