simple calculator program 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}

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;  

1import java.util.Scanner;
2
3public class Calculator {
4
5    public static void main(String[] args) {
6
7        Scanner reader = new Scanner(System.in);
8        System.out.print("Enter two numbers: ");
9
10        // nextDouble() reads the next double from the keyboard
11        double first = reader.nextDouble();
12        double second = reader.nextDouble();
13
14        System.out.print("Enter an operator (+, -, *, /): ");
15        char operator = reader.next().charAt(0);
16
17        double result;
18
19        switch(operator)
20        {
21            case '+':
22                result = first + second;
23                break;
24
25            case '-':
26                result = first - second;
27                break;
28
29            case '*':
30                result = first * second;
31                break;
32
33            case '/':
34                result = first / second;
35                break;
36
37            // operator doesn't match any case constant (+, -, *, /)
38            default:
39                System.out.printf("Error! operator is not correct");
40                return;
41        }
42
43        System.out.printf("%.1f %c %.1f = %.1f", first, operator, second, result);
44    }
45}