Java Hello World

2011-11-13T04:48:00.001-08:00

Basic Java Program
This is the first step to the java world. Here i am going to explain how can a simple string "Hello World" print or display in the command prompt. For this all we need is the JDK(java development kit).
You can download it from the link given below. If you had it, then you are ready now.
Just install it and find the path where the jdk is located and the find the bin folder (for 64bit os it is "C:\Program Files\Java\jdk1.7.0_01\bin" , for 32 bit os it isC:\Program Files (x86)\Java\jdk1.7.0_01\bin)
If you have any other version of java then you can replace the version no with yours..

Initialization Steps
Open cmd(smpliply press windows+R then enter cmd and press enter)
then type set path="C:\Program Files (x86)\Java\jdk1.7.0_01\bin"
about loaction replaced by yours
the initial steps completed.

Hello World Program

public class HelloWorld
{
public static void main(String args[])
{
System.out.println("Hello World");
}
}

simply copy this program and paste it into a text file and save it as "HelloWorld.java"
java is case sensitive. Normally the starting letters of each word in the name of a class will be Upper Case
And the file name should be the name of the class which contains public static void main

Compilation And Running
For compilation we use a command "javac" and for running we use "java" command
enter The command as shown below . for any other program only thing you have to do is just chang the file name..

Output

Download Links

JDK 7.01

Simple Calculator

2011-11-13T02:32:00.001-08:00

SIMPLE CALCULATOR PROGRAM USING J FRAME

Given Bellow Is a java Program To create a simple calculator......

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Calculator extends JFrame implements ActionListener{
    // Variables

    final int MAX_INPUT_LENGTH = 20;
    final int INPUT_MODE = 0;
    final int RESULT_MODE = 1;
    final int ERROR_MODE = 2;
    int displayMode;
    boolean clearOnNextDigit, percent;
    double lastNumber;
    String lastOperator;
    int dot;
    private JLabel jlbOutput;
    private JButton jbnButtons[];
    private JPanel jplMaster, jplBackSpace, jplControl;
    /*
    * Font(String name, int style, int size)
      Creates a new Font from the specified name, style and point size.
    */
    Font f12 = new Font("Times New Roman", 0, 12);
    Font f121 = new Font("Times New Roman", 1, 12);
    // Constructor

    public Calculator()
    {
        setBackground(Color.gray);
        jplMaster = new JPanel();
        jlbOutput = new JLabel("0");
        jlbOutput.setHorizontalTextPosition(JLabel.RIGHT);
        jlbOutput.setBackground(Color.WHITE);
        jlbOutput.setOpaque(true);
        // Add components to frame
        getContentPane().add(jlbOutput, BorderLayout.NORTH);
        jbnButtons = new JButton[23];
        //GridLayout(int rows, int cols, int hgap, int vgap)
        JPanel jplButtons = new JPanel();            // container for Jbuttons
        // Create numeric Jbuttons
        for (int i=0; i<=9; i++)
        {
            // set each Jbutton label to the value of index
            jbnButtons[i] = new JButton(String.valueOf(i));
        }
        // Create operator Jbuttons
        jbnButtons[10] = new JButton("+/-");
        jbnButtons[11] = new JButton(".");
        jbnButtons[12] = new JButton("=");
        jbnButtons[13] = new JButton("/");
        jbnButtons[14] = new JButton("*");
        jbnButtons[15] = new JButton("-");
        jbnButtons[16] = new JButton("+");
        jbnButtons[20] = new JButton("sqrt");
        jbnButtons[21] = new JButton("X^2");
        jbnButtons[22] = new JButton("1/X");
        jplBackSpace = new JPanel();
        jplBackSpace.setLayout(new GridLayout(1, 1, 2, 2));
        jbnButtons[17] = new JButton("Backspace");
        jplBackSpace.add(jbnButtons[17]);
        jplControl = new JPanel();
        jplControl.setLayout(new GridLayout(1, 2, 2 ,2));
        jbnButtons[18] = new JButton(" CE ");
        jbnButtons[19] = new JButton("C");
        jplControl.add(jbnButtons[18]);
        jplControl.add(jbnButtons[19]);
        //Setting all Numbered JButton's to Blue. The rest to Red
        for (int i=0; i<jbnButtons.length; i++)    {
            jbnButtons[i].setFont(f12);

            if (i<10)
                jbnButtons[i].setForeground(Color.blue);

            else
                jbnButtons[i].setForeground(Color.red);
        }
        // Set panel layout manager for a 5 by 4 grid
        jplButtons.setLayout(new GridLayout(5, 4, 2, 2));
        //Add buttons to keypad panel starting at top left
        // First row
        for(int i=7; i<=9; i++)        {
            jplButtons.add(jbnButtons[i]);
        }
        jplButtons.add(jbnButtons[16]);// +
        // Second row
        for(int i=4; i<=6; i++)
        {
            jplButtons.add(jbnButtons[i]);
        }
        jplButtons.add(jbnButtons[15]);// -
        // Third row
        for( int i=1; i<=3; i++)
        {
            jplButtons.add(jbnButtons[i]);
        }
        jplButtons.add(jbnButtons[14]);// *
        //4th row
        jplButtons.add(jbnButtons[10]);// +/-
        jplButtons.add(jbnButtons[0]);
        jplButtons.add(jbnButtons[11]);// .
        jplButtons.add(jbnButtons[13]);// /
        //5 th row
        jplButtons.add(jbnButtons[12]); // =
        jplButtons.add(jbnButtons[20]);// sqrt
        jplButtons.add(jbnButtons[21]);// x^2
        jplButtons.add(jbnButtons[22]);// 1/x
        jplMaster.setLayout(new BorderLayout());
        jplMaster.add(jplBackSpace, BorderLayout.WEST);
        jplMaster.add(jplControl, BorderLayout.EAST);
        jplMaster.add(jplButtons, BorderLayout.SOUTH);
        // Add components to frame
        getContentPane().add(jplMaster, BorderLayout.SOUTH);
        requestFocus();
        //activate ActionListener
        for (int i=0; i<jbnButtons.length; i++){
            jbnButtons[i].addActionListener(this);
        }
        clearAll();
        //add WindowListener for closing frame and ending program
        addWindowListener(new WindowAdapter()
            {
                public void windowClosed(WindowEvent e)
                {
                    System.exit(0);
                }
            }
        );
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }    //End of Contructor Calculator
    public void actionPerformed(ActionEvent e){
        double result = 0;
        for (int i=0; i<jbnButtons.length; i++)
        {
            if(e.getSource() == jbnButtons[i])
            {
                switch(i)
                {
                    case 0:
                        addDigitToDisplay(i);
                        break;
                    case 1:
                        addDigitToDisplay(i);
                        break;
                    case 2:
                        addDigitToDisplay(i);
                        break;
                    case 3:
                        addDigitToDisplay(i);
                        break;
                    case 4:
                        addDigitToDisplay(i);
                        break;
                    case 5:
                        addDigitToDisplay(i);
                        break;
                    case 6:
                        addDigitToDisplay(i);
                        break;
                    case 7:
                        addDigitToDisplay(i);
                        break;
                    case 8:
                        addDigitToDisplay(i);
                        break;
                    case 9:
                        addDigitToDisplay(i);
                        break;
                    case 10:    // +/-
                        processSignChange();
                        break;
                    case 11:    // decimal point
                        clearOnNextDigit = false;
                        addDecimalPoint();
                        break;
                    case 12:    // =
                        processEquals();
                        break;
                    case 13:    // divide
                        processOperator("/");
                        break;
                    case 14:    // *
                        processOperator("*");
                        break;
                    case 15:    // -
                        processOperator("-");
                        break;
                    case 16:    // +
                        processOperator("+");
                        break;
                    case 17:    // backspace
                        if (displayMode != ERROR_MODE){
                            setDisplayString(getDisplayString().substring(0,
                                        getDisplayString().length() - 1));

                            if (getDisplayString().length() < 1)
                                setDisplayString("0");
                        }
                        break;
                    case 18:    // CE
                        clearExisting();
                        break;
                    case 19:    // C
                        clearAll();
                        break;
                    case 20:
                        if (displayMode != ERROR_MODE)
                        {
                            try
                            {
                                if (getDisplayString().indexOf("-") == 0)
                                    displayError("Invalid input for function!");

                                result = Math.sqrt(getNumberInDisplay());
                                displayResult(result);
                            }

                            catch(Exception ex)
                            {
                                displayError("Invalid input for function!");
                                displayMode = ERROR_MODE;
                            }
                        }
                        break;
                    case 21:
                        double num=getNumberInDisplay();
                        result=num*num;
                        displayResult(result);
                        break;
                    case 22:
                        if (displayMode != ERROR_MODE){
                            try
                            {
                                if (getNumberInDisplay() == 0)
                                    displayError("Cannot divide by zero!");

                                result = 1 / getNumberInDisplay();
                                displayResult(result);
                            }

                            catch(Exception ex)    {
                                displayError("Cannot divide by zero!");
                                displayMode = ERROR_MODE;
                            }
                        }
                        break;
                }
            }
        }
    }
    void setDisplayString(String s){
        jlbOutput.setText(s);
    }
    String getDisplayString (){
        return jlbOutput.getText();
    }
    void addDigitToDisplay(int digit){
        if (clearOnNextDigit)
            setDisplayString("");
        String inputString = getDisplayString();
        if (inputString.indexOf("0") == 0){
            inputString = inputString.substring(1);
        }
        if ((!inputString.equals("0")||digit > 0) && inputString.length() < MAX_INPUT_LENGTH){
            setDisplayString(inputString + digit);
        }
        displayMode = INPUT_MODE;
        clearOnNextDigit = false;
    }
    void addDecimalPoint(){
        displayMode = INPUT_MODE;
        if (clearOnNextDigit)
            setDisplayString("");
        String inputString = getDisplayString();
        if (inputString.indexOf(".") < 0)
            {
            setDisplayString(new String(inputString + "."));
            //dot=0;
            }
    }
    void processSignChange(){
        if (displayMode == INPUT_MODE)
        {
            String input = getDisplayString();

            if (input.length() > 0 && !input.equals("0"))
            {
                if (input.indexOf("-") == 0)
                    setDisplayString(input.substring(1));

                else
                    setDisplayString("-" + input);
            }

        }
        else if (displayMode == RESULT_MODE)
        {
            double numberInDisplay = getNumberInDisplay();

            if (numberInDisplay != 0)
                displayResult(-numberInDisplay);
        }
    }
    void clearAll()    {
        setDisplayString("0");
        lastOperator = "0";
        lastNumber = 0;
        displayMode = INPUT_MODE;
        clearOnNextDigit = true;
    }
    void clearExisting(){
        setDisplayString("0");
        clearOnNextDigit = true;
        displayMode = INPUT_MODE;
    }
    double getNumberInDisplay()    {
        String input = jlbOutput.getText();
        return Double.parseDouble(input);
    }
    void processOperator(String op) {
        if (displayMode != ERROR_MODE)
        {
            double numberInDisplay = getNumberInDisplay();
            if (!lastOperator.equals("0"))
            {
                try
                {
                    double result = processLastOperator();
                    displayResult(result);
                    lastNumber = result;
                }
                catch (DivideByZeroException e)
                {
                }
            }
            else
            {
                lastNumber = numberInDisplay;
            }
            clearOnNextDigit = true;
            lastOperator = op;
        }
    }

    void processEquals(){
        double result = 0;
        if (displayMode != ERROR_MODE){
            try
            {
                result = processLastOperator();
                displayResult(result);
            }
            catch (DivideByZeroException e)    {
                displayError("Cannot divide by zero!");
            }
            lastOperator = "0";
        }
    }
    double processLastOperator() throws DivideByZeroException {
        double result = 0;
        double numberInDisplay = getNumberInDisplay();
        if (lastOperator.equals("/"))
        {
            if (numberInDisplay == 0)
                throw (new DivideByZeroException());

            result = lastNumber / numberInDisplay;
        }
        if (lastOperator.equals("*"))
            result = lastNumber * numberInDisplay;

        if (lastOperator.equals("-"))
            result = lastNumber - numberInDisplay;

        if (lastOperator.equals("+"))
            result = lastNumber + numberInDisplay;

        return result;
    }
    void displayResult(double result){
        setDisplayString(Double.toString(result));
        lastNumber = result;
        displayMode = RESULT_MODE;
        clearOnNextDigit = true;
    }
    void displayError(String errorMessage){
        setDisplayString(errorMessage);
        lastNumber = 0;
        displayMode = ERROR_MODE;
        clearOnNextDigit = true;
    }
    public static void main(String args[]) {
        Calculator calc = new Calculator();
        Container contentPane = calc.getContentPane();
        calc.setTitle("Calculator");
        calc.setSize(241, 217);
        calc.pack();
        calc.setLocation(400, 250);
        calc.setVisible(true);
        calc.setResizable(false);
    }
}        //End of Swing Calculator Class.

class DivideByZeroException extends Exception{
    public DivideByZeroException()
    {
        super();
    }
    public DivideByZeroException(String s)
    {
        super(s);
    }
}

OUTPUT

Java Programs For All

Java Hello World

Simple Calculator