calculator program in java

                                    /* Create Switch cases */
Scanner sc= new Scanner(System.in);
int firstNum= sc.nextInt();
int secondNum= sc.nextInt();
System.out.println("Enter an operator (+, -, *, /):");
char operator= sc.next().chartAt(0);
double result=0;
switch(operator){
  case "+":
    result+= firstNum+ secondNum;
    break;
  case "-":
    result+= firstNum-secondNum;
    break;
  case "*":
    result+= firstNum*secondNum;
    break;
  case "/":
    result+= firstNum/secondNum;
    break;
}

                                    import java.util.Scanner;


public class Calculator {


    public static void main(String[] args) {

        Scanner kb = new Scanner(System.in);

        System.out.println("Simple Calculator");

        System.out.println("\nHere are your options:");
        System.out.println("\n1. Addition");
        System.out.println("2. Subtraction");
        System.out.println("3. Division");
        System.out.println("4. Multiplication");

        System.out.print("\nWhat would you like to do?: ");
        int choice = kb.nextInt();
        System.out.println();


        if (choice == 1){
            addition();
        }
        else if (choice == 2){
            subtraction();
        }
        else if (choice == 3){
            division();
        }
        else if (choice == 4){
            multiplication();
        }

        System.out.println();
        kb.close();
    }

    public static void addition(){

        int nOne, nTwo;
        Scanner kb = new Scanner(System.in);

        System.out.println("Addition");

        System.out.print("\nFirst Number: ");
        nOne = kb.nextInt();

        System.out.print("\nSecond Number: ");
        nTwo = kb.nextInt();

        kb.close();
        System.out.println("\nSum: " + nOne + " + " + nTwo + " = " + (nOne + nTwo));
    }

    public static void subtraction(){
        int nOne, nTwo;
        Scanner kb = new Scanner(System.in);

        System.out.println("Subtraction");

        System.out.print("\nFirst Number: ");
        nOne = kb.nextInt();

        System.out.print("\nSecond Number: ");
        nTwo = kb.nextInt();

        kb.close();
        System.out.println("\nSum: " + nOne + " - " + nTwo + " = " + (nOne - nTwo));
    }

    public static void division(){
        int nOne, nTwo;
        Scanner kb = new Scanner(System.in);

        System.out.println("Division");

        System.out.print("\nFirst Number: ");
        nOne = kb.nextInt();

        System.out.print("\nSecond Number: ");
        nTwo = kb.nextInt();

        kb.close();
        System.out.println("\nSum: " + nOne + " / " + nTwo + " = " + (nOne / nTwo));
    }

    public static void multiplication(){
        int nOne, nTwo;
        Scanner kb = new Scanner(System.in);

        System.out.println("Multiplication");

        System.out.print("\nFirst Number: ");
        nOne = kb.nextInt();

        System.out.print("\nSecond Number: ");
        nTwo = kb.nextInt();

        kb.close();
        System.out.println("\nSum: " + nOne + " x " + nTwo + " = " + (nOne * nTwo));
    }
}

                                    package main;

import java.util.Scanner;

public class calculator {

    public static void greetings(){
        System.out.println("Hi welcome to the calculator made by Pepa pig made in java! :D");
    }

    public static void instruction(){
        System.out.println("Hi welcome to the calculator made by Pepa pig made in java! :D");
    }

    public static void calculator(){
        Scanner keyboardInput = new Scanner(System.in);
        String calculator;

        do {
            System.out.print("Enter your first digit: ");
            double num1 = keyboardInput.nextDouble();

            System.out.print("Enter your operator: ");
            String op = keyboardInput.next();

            System.out.print("Enter your second digit: ");
            double num2 = keyboardInput.nextDouble();

            System.out.print("= ");

            if (op.equals("+")){
                System.out.print(num1 + num2);
                System.out.println("\nYou were adding");
                System.out.println("How I know that cause I have big brain and a smart programmer ;)");
            }else if (op.equals("-")){
                System.out.print(num1 - num2);
                System.out.println("\nYou were subtracting");
                System.out.println("How I know that cause I have big brain and a smart programmer ;)");
            }else if (op.equals("*")){
                System.out.print(num1 * num2);
                System.out.println("\nYou were multiplying");
                System.out.println("How I know that cause I have big brain and a smart programmer ;)");
            }else if (op.equals("/")){
                System.out.print(num1 / num2);
                System.out.println("\nYou were dividing");
                System.out.println("How I know that cause I have big brain and a smart programmer ;)");
            }else if (op.equals("%")){
                System.out.print(num1 % num2);
                System.out.println("\nYou were remanding");
                System.out.println("How I know that cause I have big brain and a smart programmer ;)");
            }else{
                System.out.println("Invalid operator");
            }
            System.out.print("Would you like to restart the calculator? (y or n): ");
            calculator = keyboardInput.next();
        }
        while (calculator.equals("y"));

        if (calculator.equals("n")){
            System.out.println("Leave then kiddo ;-;");
        }
    }


    public static void main(String[] args) {
        greetings();
        instruction();
        calculator();
    }
}

                                    Save this file as MyCalculator.java 
to compile it use 
    javac MyCalculator.java 
to use the calcuator do this 
    java MyCalculator 
 
**********************************************/  
import java.awt.*;  
import java.awt.event.*;  
/*********************************************/  
  
public class MyCalculator extends Frame  
{  
  
public boolean setClear=true;  
double number, memValue;  
char op;  
  
String digitButtonText[] = {"7", "8", "9", "4", "5", "6", "1", "2", "3", "0", "+/-", "." };  
String operatorButtonText[] = {"/", "sqrt", "*", "%", "-", "1/X", "+", "=" };  
String memoryButtonText[] = {"MC", "MR", "MS", "M+" };  
String specialButtonText[] = {"Backspc", "C", "CE" };  
  
MyDigitButton digitButton[]=new MyDigitButton[digitButtonText.length];  
MyOperatorButton operatorButton[]=new MyOperatorButton[operatorButtonText.length];  
MyMemoryButton memoryButton[]=new MyMemoryButton[memoryButtonText.length];  
MySpecialButton specialButton[]=new MySpecialButton[specialButtonText.length];  
  
Label displayLabel=new Label("0",Label.RIGHT);  
Label memLabel=new Label(" ",Label.RIGHT);  
  
final int FRAME_WIDTH=325,FRAME_HEIGHT=325;  
final int HEIGHT=30, WIDTH=30, H_SPACE=10,V_SPACE=10;  
final int TOPX=30, TOPY=50;  
///////////////////////////  
MyCalculator(String frameText)//constructor  
{  
super(frameText);  
  
int tempX=TOPX, y=TOPY;  
displayLabel.setBounds(tempX,y,240,HEIGHT);  
displayLabel.setBackground(Color.BLUE);  
displayLabel.setForeground(Color.WHITE);  
add(displayLabel);  
  
memLabel.setBounds(TOPX,  TOPY+HEIGHT+ V_SPACE,WIDTH, HEIGHT);  
add(memLabel);  
  
// set Co-ordinates for Memory Buttons  
tempX=TOPX;   
y=TOPY+2*(HEIGHT+V_SPACE);  
for(int i=0; i<memoryButton.length; i++)  
{  
memoryButton[i]=new MyMemoryButton(tempX,y,WIDTH,HEIGHT,memoryButtonText[i], this);  
memoryButton[i].setForeground(Color.RED);  
y+=HEIGHT+V_SPACE;  
}  
  
//set Co-ordinates for Special Buttons  
tempX=TOPX+1*(WIDTH+H_SPACE); y=TOPY+1*(HEIGHT+V_SPACE);  
for(int i=0;i<specialButton.length;i++)  
{  
specialButton[i]=new MySpecialButton(tempX,y,WIDTH*2,HEIGHT,specialButtonText[i], this);  
specialButton[i].setForeground(Color.RED);  
tempX=tempX+2*WIDTH+H_SPACE;  
}  
  
//set Co-ordinates for Digit Buttons  
int digitX=TOPX+WIDTH+H_SPACE;  
int digitY=TOPY+2*(HEIGHT+V_SPACE);  
tempX=digitX;  y=digitY;  
for(int i=0;i<digitButton.length;i++)  
{  
digitButton[i]=new MyDigitButton(tempX,y,WIDTH,HEIGHT,digitButtonText[i], this);  
digitButton[i].setForeground(Color.BLUE);  
tempX+=WIDTH+H_SPACE;  
if((i+1)%3==0){tempX=digitX; y+=HEIGHT+V_SPACE;}  
}  
  
//set Co-ordinates for Operator Buttons  
int opsX=digitX+2*(WIDTH+H_SPACE)+H_SPACE;  
int opsY=digitY;  
tempX=opsX;  y=opsY;  
for(int i=0;i<operatorButton.length;i++)  
{  
tempX+=WIDTH+H_SPACE;  
operatorButton[i]=new MyOperatorButton(tempX,y,WIDTH,HEIGHT,operatorButtonText[i], this);  
operatorButton[i].setForeground(Color.RED);  
if((i+1)%2==0){tempX=opsX; y+=HEIGHT+V_SPACE;}  
}  
  
addWindowListener(new WindowAdapter()  
{  
public void windowClosing(WindowEvent ev)  
{System.exit(0);}  
});  
  
setLayout(null);  
setSize(FRAME_WIDTH,FRAME_HEIGHT);  
setVisible(true);  
}  
//////////////////////////////////  
static String getFormattedText(double temp)  
{  
String resText=""+temp;  
if(resText.lastIndexOf(".0")>0)  
    resText=resText.substring(0,resText.length()-2);  
return resText;  

                                    import java.util.Scanner;
public class Calculator {
   public static void main(String[] args) {
      double num1;
      double num2;
      double ans;
      char op;
      Scanner reader = new Scanner(System.in);
      System.out.print("Enter two numbers: ");
      num1 = reader.nextDouble();
      num2 = reader.nextDouble();
      System.out.print("\nEnter an operator (+, -, *, /): ");
      op = reader.next().charAt(0);
      switch(op) {
         case '+': ans = num1 + num2;
            break;
         case '-': ans = num1 - num2;
            break;
         case '*': ans = num1 * num2;
            break;
         case '/': ans = num1 / num2;
            break;
      default: System.out.printf("Error! Enter correct operator");
         return;
      }
      System.out.print("\nThe result is given as follows:\n");
      System.out.printf(num1 + " " + op + " " + num2 + " = " + ans);
   }
}