Java Programming

The following is for a simple calculator; a scientific calculator is more complicated. I will assume the user will press keys to have a number appear on the display; to (for example) add this with another number, the user presses "+" followed by the second number, followed by "=".

You would use a visual interface, with the number display, the digits, the equal sign, and a few operations (plus, minus, multiply, divide, ...).

As soon as the user types the second number, the first number will disappear from the screen; therefore, you have to save it into some variable.

Every time a key is pressed, you have to decide whether you should add a digit to the number in the display (if it is a digit, or a period), or whether to do a calculation (if it is +, -, *, /). If it is an operation, do the operation (conditionally, depending on the selected operation), and replace the number displayed by the new value.

This is my sample code using JAVA:

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.event.*;

import java.text.*;

import javax.swing.border.*;

class Calc extends JFrame implements ActionListener

{

private static final Font BIGGER_FONT = new Font("Tahoma", Font.BOLD, 13);

private JRadioButton decimalb,binaryb,octalb,hexab,enableb, disableb;

private JTextField _displayField, decimalTF, binaryTF, octalTF, hexaTF;

private JLabel decimalL,binaryL,octalL,hexaL;

private JButton exitb, convertb, clearb, backSpace, b9, b8, b7, b6, b5, b4, b3, b2, b1, b0, b11, b12, b13;

private JButton b14, b15, b16, b17, b18, b19, b20, b21, b22, b23, b24, b25;

private JPanel cbPanel, upperButtonPanel;

private ButtonGroup group, group2;

private boolean pluz = false;

private boolean subs = false;

private boolean multiply = false;

private boolean divide = false;

private boolean _startNumber = true;

private boolean dotCheck = false;

private String firstValue, Secondvalue;

private String _previousOp = "=";

private DecimalFormat df = new DecimalFormat("###,###,###.##");

private CalculatorLogic calLogic = new CalculatorLogic();

public static void main(String[] args) {

try {

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

} catch (Exception unused) {

;

}

Calc window = new Calc();

window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

window.setVisible(true);

}

public Calc()

{

super("Calculator With Number System Converter");

_displayField = new JTextField("", 15);

_displayField.setHorizontalAlignment(JTextField.RIGHT);

_displayField.setFont(BIGGER_FONT);

_displayField.setEditable(false);

_displayField.setBackground(Color.WHITE);

upperButtonPanel = new JPanel();

upperButtonPanel.setLayout(new FlowLayout());

upperButtonPanel.setBackground(Color.lightGray);

upperButtonPanel.setPreferredSize(new Dimension(170, 300));

decimalb = new JRadioButton("Decimal", false);

binaryb = new JRadioButton("Binary", false);

octalb = new JRadioButton("Octal", false);

hexab = new JRadioButton("Hexadecimal", false);

decimalb.setFont(BIGGER_FONT);

binaryb.setFont(BIGGER_FONT);

octalb.setFont(BIGGER_FONT);

hexab.setFont(BIGGER_FONT);

decimalb.addActionListener(this);

binaryb.addActionListener(this);

octalb.addActionListener(this);

hexab.addActionListener(this);

group = new ButtonGroup();

group.add(decimalb);

group.add(binaryb);

group.add(octalb);

group.add(hexab);

upperButtonPanel.add(decimalb);

upperButtonPanel.add(binaryb);

upperButtonPanel.add(octalb);

upperButtonPanel.add(hexab);

upperButtonPanel.setVisible(false);

JPanel panel = new JPanel(new GridLayout(10, 1));

panel.setPreferredSize(new Dimension(300, 300));

panel.setBorder(new BevelBorder(BevelBorder.LOWERED));

decimalTF = new JTextField(20);

binaryTF = new JTextField(20);

octalTF = new JTextField(20);

hexaTF = new JTextField(20);

decimalTF.setEditable(false);

binaryTF.setEditable(false);

octalTF.setEditable(false);

hexaTF.setEditable(false);

decimalTF.setBackground(Color.WHITE);

binaryTF.setBackground(Color.WHITE);

octalTF.setBackground(Color.WHITE);

hexaTF.setBackground(Color.WHITE);

decimalTF.setFont(BIGGER_FONT);

binaryTF.setFont(BIGGER_FONT);

octalTF.setFont(BIGGER_FONT);

hexaTF.setFont(BIGGER_FONT);

decimalTF.setVisible(false);

binaryTF.setVisible(false);

octalTF.setVisible(false);

hexaTF.setVisible(false);

decimalL = new JLabel("Decimal Value");

binaryL = new JLabel("Binary Value");

octalL = new JLabel("Octal Value");

hexaL = new JLabel("Hexadecimal Value");

decimalL.setFont(BIGGER_FONT);

binaryL.setFont(BIGGER_FONT);

octalL.setFont(BIGGER_FONT);

hexaL.setFont(BIGGER_FONT);

decimalL.setVisible(false);

binaryL.setVisible(false);

octalL.setVisible(false);

hexaL.setVisible(false);

panel.add(decimalL);

panel.add(decimalTF);

panel.add(binaryL);

panel.add(binaryTF);

panel.add(octalL);

panel.add(octalTF);

panel.add(hexaL);

panel.add(hexaTF);

upperButtonPanel.add(panel);

add(upperButtonPanel, BorderLayout.NORTH);

JPanel buttonPanel = new JPanel();

buttonPanel.setLayout(new GridLayout(5, 2, 5, 5));

buttonPanel.setBackground(Color.lightGray);

buttonPanel.setBorder(new BevelBorder(BevelBorder.LOWERED));

b9 = new JButton("9");

b8 = new JButton("8");

b7 = new JButton("7");

b6 = new JButton("6");

b5 = new JButton("5");

b4 = new JButton("4");

b3 = new JButton("3");

b2 = new JButton("2");

b1 = new JButton("1");

b0 = new JButton("0");

b11 = new JButton(".");

b12 = new JButton("/");

b13 = new JButton("*");

b14 = new JButton("-");

b15 = new JButton("+");

b16 = new JButton("A");

b17 = new JButton("B");

b18 = new JButton("C");

b19 = new JButton("D");

b20 = new JButton("E");

b21 = new JButton("F");

b22 = new JButton("=");

b23 = new JButton("sqrt");

b24 = new JButton("x\u00B2");

b25 = new JButton("x\u00B3");

b1.setFont(BIGGER_FONT);

b2.setFont(BIGGER_FONT);

b3.setFont(BIGGER_FONT);

b4.setFont(BIGGER_FONT);

b5.setFont(BIGGER_FONT);

b6.setFont(BIGGER_FONT);

b7.setFont(BIGGER_FONT);

b8.setFont(BIGGER_FONT);

b9.setFont(BIGGER_FONT);

b0.setFont(BIGGER_FONT);

b11.setFont(BIGGER_FONT);

b12.setFont(BIGGER_FONT);

b13.setFont(BIGGER_FONT);

b14.setFont(BIGGER_FONT);

b15.setFont(BIGGER_FONT);

b16.setFont(BIGGER_FONT);

b17.setFont(BIGGER_FONT);

b18.setFont(BIGGER_FONT);

b19.setFont(BIGGER_FONT);

b20.setFont(BIGGER_FONT);

b21.setFont(BIGGER_FONT);

b22.setFont(BIGGER_FONT);

b23.setFont(BIGGER_FONT);

b24.setFont(BIGGER_FONT);

b25.setFont(BIGGER_FONT);

b1.addActionListener(this);

b2.addActionListener(this);

b3.addActionListener(this);

b4.addActionListener(this);

b5.addActionListener(this);

b6.addActionListener(this);

b7.addActionListener(this);

b8.addActionListener(this);

b9.addActionListener(this);

b0.addActionListener(this);

b11.addActionListener(this);

b12.addActionListener(this);

b13.addActionListener(this);

b14.addActionListener(this);

b15.addActionListener(this);

b16.addActionListener(this);

b17.addActionListener(this);

b18.addActionListener(this);

b19.addActionListener(this);

b20.addActionListener(this);

b21.addActionListener(this);

b22.addActionListener(this);

b23.addActionListener(this);

b24.addActionListener(this);

b25.addActionListener(this);

b16.setEnabled(false);

b17.setEnabled(false);

b18.setEnabled(false);

b19.setEnabled(false);

b20.setEnabled(false);

b21.setEnabled(false);

buttonPanel.add(b7);

buttonPanel.add(b8);

buttonPanel.add(b9);

buttonPanel.add(b12);

buttonPanel.add(b13);

buttonPanel.add(b15);

buttonPanel.add(b4);

buttonPanel.add(b5);

buttonPanel.add(b6);

buttonPanel.add(b15);

buttonPanel.add(b14);

buttonPanel.add(b11);

buttonPanel.add(b1);

buttonPanel.add(b2);

buttonPanel.add(b3);

buttonPanel.add(b0);

buttonPanel.add(b22);

buttonPanel.add(b16);

buttonPanel.add(b17);

buttonPanel.add(b18);

buttonPanel.add(b11);

buttonPanel.add(b23);

buttonPanel.add(b19);

buttonPanel.add(b20);

buttonPanel.add(b21);

buttonPanel.add(b24);

buttonPanel.add(b25);

add(buttonPanel);

group2 = new ButtonGroup();

disableb = new JRadioButton("Disable Converter", true);

enableb = new JRadioButton("Enable Converter", false);

disableb.setFont(BIGGER_FONT);

enableb.setFont(BIGGER_FONT);

disableb.addActionListener(this);

enableb.addActionListener(this);

group2.add(disableb);

group2.add(enableb);

cbPanel = new JPanel(new GridLayout(3, 3));

cbPanel.setBorder(new BevelBorder(BevelBorder.RAISED));

cbPanel.add(disableb);

cbPanel.add(enableb);

convertb = new JButton("Convert");

clearb = new JButton("Clear");

exitb = new JButton("Exit");

backSpace = new JButton("BackSpace");

convertb.addActionListener(this);

clearb.addActionListener(this);

exitb.addActionListener(this);

backSpace.addActionListener(this);

convertb.setFont(BIGGER_FONT);

clearb.setFont(BIGGER_FONT);

exitb.setFont(BIGGER_FONT);

backSpace.setFont(BIGGER_FONT);

cbPanel.add(convertb);

cbPanel.add(clearb);

cbPanel.add(backSpace);

cbPanel.add(exitb);

convertb.setEnabled(false);

JPanel content2 = new JPanel();

content2.setLayout(new BorderLayout(5, 5));

content2.add(_displayField, BorderLayout.NORTH);

content2.add(buttonPanel , BorderLayout.CENTER);

content2.add(cbPanel, BorderLayout.SOUTH);

add(content2, BorderLayout.SOUTH);

this.setSize(340, 300);

this.setResizable(false);

this.setLocationRelativeTo(null);

}

public void actionPerformed(ActionEvent e)

{

try{

if(decimalb.isSelected())

{

b0.setEnabled(true);

b1.setEnabled(true);

b2.setEnabled(true);

b3.setEnabled(true);

b4.setEnabled(true);

b5.setEnabled(true);

b6.setEnabled(true);

b7.setEnabled(true);

b8.setEnabled(true);

b9.setEnabled(true);

b16.setEnabled(false);

b17.setEnabled(false);

b18.setEnabled(false);

b19.setEnabled(false);

b20.setEnabled(false);

b21.setEnabled(false);

}

else if(binaryb.isSelected())

{

b2.setEnabled(false);

b3.setEnabled(false);

b4.setEnabled(false);

b5.setEnabled(false);

b6.setEnabled(false);

b7.setEnabled(false);

b8.setEnabled(false);

b9.setEnabled(false);

b16.setEnabled(false);

b17.setEnabled(false);

b18.setEnabled(false);

b19.setEnabled(false);

b20.setEnabled(false);

b21.setEnabled(false);

}

else if(octalb.isSelected())

{

b0.setEnabled(true);

b1.setEnabled(true);

b2.setEnabled(true);

b3.setEnabled(true);

b4.setEnabled(true);

b5.setEnabled(true);

b6.setEnabled(true);

b7.setEnabled(true);

b16.setEnabled(false);

b17.setEnabled(false);

b18.setEnabled(false);

b19.setEnabled(false);

b20.setEnabled(false);

b21.setEnabled(false);

b8.setEnabled(false);

b9.setEnabled(false);

}

else if(hexab.isSelected())

{

b0.setEnabled(true);

b1.setEnabled(true);

b2.setEnabled(true);

b3.setEnabled(true);

b4.setEnabled(true);

b5.setEnabled(true);

b6.setEnabled(true);

b7.setEnabled(true);

b8.setEnabled(true);

b9.setEnabled(true);

b16.setEnabled(true);

b17.setEnabled(true);

b18.setEnabled(true);

b19.setEnabled(true);

b20.setEnabled(true);

b21.setEnabled(true);

}

if((e.getActionCommand().equals("Convert")) && decimalb.isSelected())

{

String input, bin="",oct="",hex="";

int rem,rem2,rem3,len;

char x;

input = _displayField.getText().trim();

try{

if(input.equals(""))

throw new Exception("Error");

else

len = input.length();

int num = Integer.parseInt(input);

while(num>0)

{

rem = num%2;

num/=2;

bin = rem + bin;

}

binaryTF.setText(bin);

decimalTF.setText(input);

int num2 = Integer.parseInt(input);

while(num2>0)

{

rem2 = num2%8;

oct = rem2 + oct;

num2/=8;

}

octalTF.setText(oct);

int num3 = Integer.parseInt(input);

while(num3>0)

{

rem3 = num3%16;

if(rem3<10)

hex = rem3 + hex;

else if(rem3 0)

{

JOptionPane.showMessageDialog(null,"Can't divide by zero", "Error Message", JOptionPane.ERROR_MESSAGE);

return 0;

}

else

return (a / b);

}

public double stringToDouble(String a)

{

return Double.parseDouble(a);

}

}

Exception handling in Java is done through a try-catch-finally block. The "try" block of code is where you put the code which may throw an exception. The "catch" block of code is where you put the code which will execute after an exception is thrown in the try block. This is often used to display an error message, or to mitigate problems caused by the exception. The "finally" block is where you put code that you want to execute after the try and catch blocks have been processed.

// example code for catching exception while reading from a file

try {

// this line of code can throw a FileNotFoundException

FileReader in = new FileReader("myfile.txt");

// this line of code can throw an IOException

in.read();

} catch(FileNotFoundException ex) { // catch first exception type

System.err.println("Cannot find myfile.txt!");

} catch(IOException ex) { //catch second exception type

System.err.println("Cannot read from myfile.txt!");

} finally { // no matter what we want to close the file, so do it here

// however, this line can also cause an exception, so we need to catch that, too

try {

in.close();

catch(IOException ex) {

// not much we can do about an exception that occurs here

}

}

a small amount of information sent by a servlet to a Web browser, saved by the browser, and later sent back to the server. A cookie's value can uniquely identify a client, so cookies are commonly used for session management.

A cookie has a name, a single value, and optional attributes such as a comment, path and domain qualifiers, a maximum age, and a version number. Some Web browsers have bugs in how they handle the optional attributes, so use them sparingly to improve the interoperability of your servlets.

The servlet sends cookies to the browser by using the HttpServletResponse.addCookie(javax.servlet.http.Cookie) method, which adds fields to HTTP response headers to send cookies to the browser, one at a time. The browser is expected to support 20 cookies for each Web server, 300 cookies total, and may limit cookie size to 4 KB each.

The browser returns cookies to the servlet by adding fields to HTTP request headers. Cookies can be retrieved from a request by using the HttpServletRequest.getCookies() method. Several cookies might have the same name but different path attributes.

Cookies affect the caching of the Web pages that use them. HTTP 1.0 does not cache pages that use cookies created with this class. This class does not support the cache control defined with HTTP 1.1.

"Platform neutral" means that Java does not depend directly on the underlying operating system; the same binary Java classes will run on any platform that support the target version of Java that those classes use, such as Windows, Linux, and Mac OS.

Java has enhanced security opposed to a native binary (e.g. a program written in C++) in the sense that an additional layer of security is implemented in the Java VM that reduces promiscuous behavior (such as accessing the hard drive when running as an applet). Java is arguably not as secure as some other languages (such as Mono/.NET, which can be statically verified safe without executing the program), but it is generally more secure than non-VM-based languages because of the extra layer of security.

Java

java takes command line arguments from user so as to execute the program,that's why we always mention arguments for main() , now java always assumes that the argumetns are of String type which may be appropriately converted to any other type later. that is why we pass string array to hold the command line argumetns supplied by the user.

Borobudur was an early kingdom centered on the island of java and Bali.

The java.io.File class in Java has a delete() method to delete the file.

See related link for details.

HTC 620 uses 4.4 android which partially supports java but it does not run oracle JVM or even oracle java.

To write down observations based on notes that have been taken

A ROM image for a video game is basically a software copy of a hardware chip. There is no such thing for Java, or any game written in Java.

The following example rounds pi to an integer:

System.out.println(Math.round(Math.PI));

The following example rounds pi to an integer:

System.out.println(Math.round(Math.PI));

The following example rounds pi to an integer:

System.out.println(Math.round(Math.PI));

The following example rounds pi to an integer:

System.out.println(Math.round(Math.PI));

Please rephrase your question. An array usually has a fixed size and I don't recall ever having to "go below its size". This implies that the missing elements are not within the range of the array.

Constructors have the same name as the class itself and they do not specify a return type, not even void because they return the instance of the class itself.

Because constructors have the same name as the class then they allow method overloading and also save memory and execution time of program.

Program release memory of constructors function after using this function and it reduce program complexity.

Currency Source Code Using JCreator

Superclasses are considered fragile because seemingly safe modifications to a super class, when inherited by the derived classes, may cause the derived classes to malfunction.

The Javac is the java compiler javac.exe is a process associated with Java(TM) 2 Platform Standard Edition 5.0 Update 5 from Sun Microsystems, Inc.. Java Capusal this is a java compiler

The purpose of Java Sun software is to allow one to play online games, chat with people from around the world, viewing 3D images and run videos on the internet from a desktop, laptop or mobile device.

200 instructions only.

#include <stdio.h>

#include <conio.h>

//Sorting an array with a single FOR loop. No complex coding and testing with multiple array sizes.

int main()

{ clrscr();

int xlist[5]={5,3,4,1,2};

int i,temp;

for (i=0;i<4;)

{

if (xlist[i]<xlist[i+1])

i++;

else

{ temp=xlist[i];

xlist[i]=xlist[i+1];

xlist[i+1]=temp;

i=0;

}

}

for (i=0;i<5;i++)

{ printf("%d ",xlist[i]); }

getch();

return 0;

}

A class declared as final means that no other class can inherit from it.

I've written a Blog about the same topic in relation to some events in my country: http://srijanfoundation.wordpress.com/2007/11/02/chak-de-india-the-non-message/.

Love,

Rahul Dewan

--

http://srijanfoundation.wordpress.com/

http://srijantech.wordpress.com/

http://www.srijan.in

It means end the function. Functions automatically end when execution reaches the end of the function, but you can return from a function at any point within the function with a return statement.

If the function returns a value to its caller, you must provide a reachable return statement along with the value you wish to return.