how to make a calculator in java

1import java.util.Scanner;
2public class Calculator {
3   public static void main(String[] args) {
4      double num1;
5      double num2;
6      double ans;
7      char op;
8      Scanner reader = new Scanner(System.in);
9      System.out.print("Enter two numbers: ");
10      num1 = reader.nextDouble();
11      num2 = reader.nextDouble();
12      System.out.print("\nEnter an operator (+, -, *, /): ");
13      op = reader.next().charAt(0);
14      switch(op) {
15         case '+': ans = num1 + num2;
16            break;
17         case '-': ans = num1 - num2;
18            break;
19         case '*': ans = num1 * num2;
20            break;
21         case '/': ans = num1 / num2;
22            break;
23      default: System.out.printf("Error! Enter correct operator");
24         return;
25      }
26      System.out.print("\nThe result is given as follows:\n");
27      System.out.printf(num1 + " " + op + " " + num2 + " = " + ans);
28   }
29}

1// this was all coded by me, to use it get Eclipse, or IntelliJ and make a new
2// Java Project
3
4package javaCode;
5
6import java.util.Scanner;
7
8public class testCode {
9
10	public static void main(String[] args) {
11		
12		Scanner scan = new Scanner(System.in);
13		
14		System.out.println("Would you like to Add, Subtract, Divide, or Multiply?");
15		
16		String mathType = scan.next();
17		
18		if (mathType.equalsIgnoreCase("add")) {
19			System.out.println("Whats the first number you want to add?");
20			
21			int firstNumber = scan.nextInt();
22			
23			System.out.println(firstNumber + " + ");
24			System.out.println("Enter your second number");
25			
26			int secondNumber = scan.nextInt();
27			
28			System.out.println(firstNumber + " + " + secondNumber + " =");
29			System.out.println(firstNumber + secondNumber);
30			
31		} else if (mathType.equalsIgnoreCase("subtract")) {
32			System.out.println("Whats the first number you want to subtract?");
33			
34			int firstNumber = scan.nextInt();
35			
36			System.out.println(firstNumber + " - ");
37			System.out.println("Enter your second number");
38			
39			int secondNumber = scan.nextInt();
40			
41			System.out.println(firstNumber + " - " + secondNumber + " =");
42			System.out.println(firstNumber - secondNumber);
43		} else if (mathType.equalsIgnoreCase("divide")) {
44			System.out.println("Whats the first number you want to divide?");
45			
46			int firstNumber = scan.nextInt();
47			
48			System.out.println(firstNumber + " % ");
49			System.out.println("Enter your second number");
50			
51			int secondNumber = scan.nextInt();
52			
53			System.out.println(firstNumber + " % " + secondNumber + " =");
54			System.out.println(firstNumber / secondNumber);
55		} else if (mathType.equalsIgnoreCase("multiply")){
56			System.out.println("Whats the first number you want to multiply?");
57			
58			int firstNumber = scan.nextInt();
59			
60			System.out.println(firstNumber + " x ");
61			System.out.println("Enter your second number");
62			
63			int secondNumber = scan.nextInt();
64			
65			System.out.println(firstNumber + " x " + secondNumber + " =");
66			System.out.println(firstNumber * secondNumber);
67		}
68		
69	}
70
71}

1Save this file as MyCalculator.java 
2to compile it use 
3    javac MyCalculator.java 
4to use the calcuator do this 
5    java MyCalculator 
6 
7**********************************************/  
8import java.awt.*;  
9import java.awt.event.*;  
10/*********************************************/  
11  
12public class MyCalculator extends Frame  
13{  
14  
15public boolean setClear=true;  
16double number, memValue;  
17char op;  
18  
19String digitButtonText[] = {"7", "8", "9", "4", "5", "6", "1", "2", "3", "0", "+/-", "." };  
20String operatorButtonText[] = {"/", "sqrt", "*", "%", "-", "1/X", "+", "=" };  
21String memoryButtonText[] = {"MC", "MR", "MS", "M+" };  
22String specialButtonText[] = {"Backspc", "C", "CE" };  
23  
24MyDigitButton digitButton[]=new MyDigitButton[digitButtonText.length];  
25MyOperatorButton operatorButton[]=new MyOperatorButton[operatorButtonText.length];  
26MyMemoryButton memoryButton[]=new MyMemoryButton[memoryButtonText.length];  
27MySpecialButton specialButton[]=new MySpecialButton[specialButtonText.length];  
28  
29Label displayLabel=new Label("0",Label.RIGHT);  
30Label memLabel=new Label(" ",Label.RIGHT);  
31  
32final int FRAME_WIDTH=325,FRAME_HEIGHT=325;  
33final int HEIGHT=30, WIDTH=30, H_SPACE=10,V_SPACE=10;  
34final int TOPX=30, TOPY=50;  
35///////////////////////////  
36MyCalculator(String frameText)//constructor  
37{  
38super(frameText);  
39  
40int tempX=TOPX, y=TOPY;  
41displayLabel.setBounds(tempX,y,240,HEIGHT);  
42displayLabel.setBackground(Color.BLUE);  
43displayLabel.setForeground(Color.WHITE);  
44add(displayLabel);  
45  
46memLabel.setBounds(TOPX,  TOPY+HEIGHT+ V_SPACE,WIDTH, HEIGHT);  
47add(memLabel);  
48  
49// set Co-ordinates for Memory Buttons  
50tempX=TOPX;   
51y=TOPY+2*(HEIGHT+V_SPACE);  
52for(int i=0; i<memoryButton.length; i++)  
53{  
54memoryButton[i]=new MyMemoryButton(tempX,y,WIDTH,HEIGHT,memoryButtonText[i], this);  
55memoryButton[i].setForeground(Color.RED);  
56y+=HEIGHT+V_SPACE;  
57}  
58  
59//set Co-ordinates for Special Buttons  
60tempX=TOPX+1*(WIDTH+H_SPACE); y=TOPY+1*(HEIGHT+V_SPACE);  
61for(int i=0;i<specialButton.length;i++)  
62{  
63specialButton[i]=new MySpecialButton(tempX,y,WIDTH*2,HEIGHT,specialButtonText[i], this);  
64specialButton[i].setForeground(Color.RED);  
65tempX=tempX+2*WIDTH+H_SPACE;  
66}  
67  
68//set Co-ordinates for Digit Buttons  
69int digitX=TOPX+WIDTH+H_SPACE;  
70int digitY=TOPY+2*(HEIGHT+V_SPACE);  
71tempX=digitX;  y=digitY;  
72for(int i=0;i<digitButton.length;i++)  
73{  
74digitButton[i]=new MyDigitButton(tempX,y,WIDTH,HEIGHT,digitButtonText[i], this);  
75digitButton[i].setForeground(Color.BLUE);  
76tempX+=WIDTH+H_SPACE;  
77if((i+1)%3==0){tempX=digitX; y+=HEIGHT+V_SPACE;}  
78}  
79  
80//set Co-ordinates for Operator Buttons  
81int opsX=digitX+2*(WIDTH+H_SPACE)+H_SPACE;  
82int opsY=digitY;  
83tempX=opsX;  y=opsY;  
84for(int i=0;i<operatorButton.length;i++)  
85{  
86tempX+=WIDTH+H_SPACE;  
87operatorButton[i]=new MyOperatorButton(tempX,y,WIDTH,HEIGHT,operatorButtonText[i], this);  
88operatorButton[i].setForeground(Color.RED);  
89if((i+1)%2==0){tempX=opsX; y+=HEIGHT+V_SPACE;}  
90}  
91  
92addWindowListener(new WindowAdapter()  
93{  
94public void windowClosing(WindowEvent ev)  
95{System.exit(0);}  
96});  
97  
98setLayout(null);  
99setSize(FRAME_WIDTH,FRAME_HEIGHT);  
100setVisible(true);  
101}  
102//////////////////////////////////  
103static String getFormattedText(double temp)  
104{  
105String resText=""+temp;  
106if(resText.lastIndexOf(".0")>0)  
107    resText=resText.substring(0,resText.length()-2);  
108return resText;  

1package main;
2
3import java.util.Scanner;
4
5public class calculator {
6
7    public static void greetings(){
8        System.out.println("Hi welcome to the calculator made by Pepa pig made in java! :D");
9    }
10
11    public static void instruction(){
12        System.out.println("Hi welcome to the calculator made by Pepa pig made in java! :D");
13    }
14
15    public static void calculator(){
16        Scanner keyboardInput = new Scanner(System.in);
17        String calculator;
18
19        do {
20            System.out.print("Enter your first digit: ");
21            double num1 = keyboardInput.nextDouble();
22
23            System.out.print("Enter your operator: ");
24            String op = keyboardInput.next();
25
26            System.out.print("Enter your second digit: ");
27            double num2 = keyboardInput.nextDouble();
28
29            System.out.print("= ");
30
31            if (op.equals("+")){
32                System.out.print(num1 + num2);
33                System.out.println("\nYou were adding");
34                System.out.println("How I know that cause I have big brain and a smart programmer ;)");
35            }else if (op.equals("-")){
36                System.out.print(num1 - num2);
37                System.out.println("\nYou were subtracting");
38                System.out.println("How I know that cause I have big brain and a smart programmer ;)");
39            }else if (op.equals("*")){
40                System.out.print(num1 * num2);
41                System.out.println("\nYou were multiplying");
42                System.out.println("How I know that cause I have big brain and a smart programmer ;)");
43            }else if (op.equals("/")){
44                System.out.print(num1 / num2);
45                System.out.println("\nYou were dividing");
46                System.out.println("How I know that cause I have big brain and a smart programmer ;)");
47            }else if (op.equals("%")){
48                System.out.print(num1 % num2);
49                System.out.println("\nYou were remanding");
50                System.out.println("How I know that cause I have big brain and a smart programmer ;)");
51            }else{
52                System.out.println("Invalid operator");
53            }
54            System.out.print("Would you like to restart the calculator? (y or n): ");
55            calculator = keyboardInput.next();
56        }
57        while (calculator.equals("y"));
58
59        if (calculator.equals("n")){
60            System.out.println("Leave then kiddo ;-;");
61        }
62    }
63
64
65    public static void main(String[] args) {
66        greetings();
67        instruction();
68        calculator();
69    }
70}

1import java.util.Scanner;
2
3class Main {
4  public static void main(String[] args) {
5
6    char operator;
7    Double number1, number2, result;
8
9    // create an object of Scanner class
10    Scanner input = new Scanner(System.in);
11
12    // ask users to enter operator
13    System.out.println("Choose an operator: +, -, *, or /");
14    operator = input.next().charAt(0);
15
16    // ask users to enter numbers
17    System.out.println("Enter first number");
18    number1 = input.nextDouble();
19
20    System.out.println("Enter second number");
21    number2 = input.nextDouble();
22
23    switch (operator) {
24
25      // performs addition between numbers
26      case '+':
27        result = number1 + number2;
28        System.out.println(number1 + " + " + number2 + " = " + result);
29        break;
30
31      // performs subtraction between numbers
32      case '-':
33        result = number1 - number2;
34        System.out.println(number1 + " - " + number2 + " = " + result);
35        break;
36
37      // performs multiplication between numbers
38      case '*':
39        result = number1 * number2;
40        System.out.println(number1 + " * " + number2 + " = " + result);
41        break;
42
43      // performs division between numbers
44      case '/':
45        result = number1 / number2;
46        System.out.println(number1 + " / " + number2 + " = " + result);
47        break;
48
49      default:
50        System.out.println("Invalid operator!");
51        break;
52    }
53
54    input.close();
55  }
56}

1import java.util.Scanner;
2
3
4public class Calculator {
5
6
7    public static void main(String[] args) {
8
9        Scanner kb = new Scanner(System.in);
10
11        System.out.println("Simple Calculator");
12
13        System.out.println("\nHere are your options:");
14        System.out.println("\n1. Addition");
15        System.out.println("2. Subtraction");
16        System.out.println("3. Division");
17        System.out.println("4. Multiplication");
18
19        System.out.print("\nWhat would you like to do?: ");
20        int choice = kb.nextInt();
21        System.out.println();
22
23
24        if (choice == 1){
25            addition();
26        }
27        else if (choice == 2){
28            subtraction();
29        }
30        else if (choice == 3){
31            division();
32        }
33        else if (choice == 4){
34            multiplication();
35        }
36
37        System.out.println();
38        kb.close();
39    }
40
41    public static void addition(){
42
43        int nOne, nTwo;
44        Scanner kb = new Scanner(System.in);
45
46        System.out.println("Addition");
47
48        System.out.print("\nFirst Number: ");
49        nOne = kb.nextInt();
50
51        System.out.print("\nSecond Number: ");
52        nTwo = kb.nextInt();
53
54        kb.close();
55        System.out.println("\nSum: " + nOne + " + " + nTwo + " = " + (nOne + nTwo));
56    }
57
58    public static void subtraction(){
59        int nOne, nTwo;
60        Scanner kb = new Scanner(System.in);
61
62        System.out.println("Subtraction");
63
64        System.out.print("\nFirst Number: ");
65        nOne = kb.nextInt();
66
67        System.out.print("\nSecond Number: ");
68        nTwo = kb.nextInt();
69
70        kb.close();
71        System.out.println("\nSum: " + nOne + " - " + nTwo + " = " + (nOne - nTwo));
72    }
73
74    public static void division(){
75        int nOne, nTwo;
76        Scanner kb = new Scanner(System.in);
77
78        System.out.println("Division");
79
80        System.out.print("\nFirst Number: ");
81        nOne = kb.nextInt();
82
83        System.out.print("\nSecond Number: ");
84        nTwo = kb.nextInt();
85
86        kb.close();
87        System.out.println("\nSum: " + nOne + " / " + nTwo + " = " + (nOne / nTwo));
88    }
89
90    public static void multiplication(){
91        int nOne, nTwo;
92        Scanner kb = new Scanner(System.in);
93
94        System.out.println("Multiplication");
95
96        System.out.print("\nFirst Number: ");
97        nOne = kb.nextInt();
98
99        System.out.print("\nSecond Number: ");
100        nTwo = kb.nextInt();
101
102        kb.close();
103        System.out.println("\nSum: " + nOne + " x " + nTwo + " = " + (nOne * nTwo));
104    }
105}