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Posts tagged Java

Java – part 11

Sep17
2011 Leave a Comment Written by Eliott

Some loops to munch on

1. The ‘for’ loop:

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for(int i = 1; i < 10; i++){
	System.out.println("Hello World!");
}

You’ve seen it before so I wont go into detail however note the definition of type on Line 1, int i.

2. The while loop:

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int i = 1;
while(i < 10){
	System.out.println("Hello World!");
	i++;
}

Again, nothing too new but this is Java.

3. The ‘do-while’ loop:

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int i = 1;
do {
	System.out.println("Hello World!");
	i++;
} while(i < 10)

This is the while loop but switched around as it performs the action before doing any checks at all.

Posted in Tutorials - Tagged

Java – part 10

Sep15
2011 Leave a Comment Written by Eliott

Confirming the choice

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String message = "Do you want to Exit?";
String title = "Really quit?";
int reply = JOptionPane.showConfirmDialog(null, message, title, JOptionPane.YES_NO_OPTION);
if(reply == JOptionPane.YES_OPTION){
      System.exit(0);
}

As you can see we can detect which button was pressed using an identifier or an integer. 0, 1 and 2 each corresponding to the relative buttons from left to right.

The possibilities are as follows:

DEFAULT_OPTION
YES_NO_OPTION
YES_NO_CANCEL_OPTION
OK_CANCEL_OPTION

Posted in Tutorials - Tagged

Java – part 9

Sep13
2011 Leave a Comment Written by Eliott

Messages

Thats right, messages. We will provide information to the user using the same JOptionPane library.

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JOptionPane.showMessageDialog(null, "Hello, my name is Eliott");

Again, it really is that simple!

Posted in Tutorials - Tagged

Java – part 8

Sep11
2011 Leave a Comment Written by Eliott

Image Icons

Remember that I said we would cover icons? Well let’s do it now.

Wherever you can use icons you simply need to do the following…

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ImageIcon icon =  createImageIcon("images/middle.gif", "My icon :)");

And it really is that easy!

Posted in Tutorials - Tagged

Java – part 7

Sep09
2011 Leave a Comment Written by Eliott

Input Boxes Continued

The thing is, that input box could accept any input. You can limit it by doing the following:
(ignore frame and icon, we will cover those later)

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Object[] possibilities = {"Male", "Female", "Both?"};
String s = (String)JOptionPane.showInputDialog(
                    frame,
                    "Which are you?:",
                    "Information",
                    JOptionPane.PLAIN_MESSAGE,
                    icon,
                    possibilities,
                    possibilities[0]);
 
//If a string was returned, say so.
if ((s != null) && (s.length() > 0)) {
System.out.println("You are: "+s);
}else{
//They haven't selected anything.
System.out.println("Is it private?");
}
Posted in Tutorials - Tagged

Java – part 6

Sep07
2011 Leave a Comment Written by Eliott

Input Boxes

This one needs a library…
Not a real library but just an import to some extra code.

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import javax.swing.JOptionPane

And then after your class and main function you might want to run something like this:

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String response = JOptionPane.showInputDialog(null, "What is your name?", "Enter your name", JOptionPane.QUESTION_MESSAGE);

The first parameter is a frame, you could dump this into a JFrame or null if not.
The second is the text to be displayed
Then the window title
And finally the input type

These are all valid input types:

  • ERROR_MESSAGE
  • INFORMATION_MESSAGE
  • WARNING_MESSAGE
  • QUESTION_MESSAGE
  • PLAIN_MESSAGE
Posted in Tutorials - Tagged

Java – part 5

Sep05
2011 Leave a Comment Written by Eliott

Arrays

20111021-100101 AM.jpg

An array is a container object holding a fixed amount of objects of a single type, e.g 10 strings, 5 integers.

And because it is zero based the first element, first object in the array, is referenced as 0…

This is the long way:

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int[] anArray; // declares an array of integers
anArray = new int[10]; // allocates memory for 10 integers
 
anArray[0] = 100; // initialize first element
anArray[1] = 200; // initialize second element
anArray[2] = 300; // etc.
anArray[3] = 400;
anArray[4] = 500;
anArray[5] = 600;
anArray[6] = 700;
anArray[7] = 800;
anArray[8] = 900;
anArray[9] = 1000;
 
System.out.println("Element at index 0: " + anArray[0]);
System.out.println("Element at index 1: " + anArray[1]);
System.out.println("Element at index 2: " + anArray[2]);
System.out.println("Element at index 3: " + anArray[3]);
System.out.println("Element at index 4: " + anArray[4]);
System.out.println("Element at index 5: " + anArray[5]);
System.out.println("Element at index 6: " + anArray[6]);
System.out.println("Element at index 7: " + anArray[7]);
System.out.println("Element at index 8: " + anArray[8]);
System.out.println("Element at index 9: " + anArray[9]);

Here’s the short way:

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int[] anArray = {100, 200, 300}

See, it’s really that easy…

Posted in Tutorials - Tagged

Java – part 4

Sep03
2011 Leave a Comment Written by Eliott

More?

Not really,must something cool I thought that I would share with the world.

Using Underscore Characters in Numeric Literals

In Java SE 7 and later, any number of underscore characters (_) can appear anywhere between digits in a numerical literal. This feature enables you, for example. to separate groups of digits in numeric literals, which can improve the readability of your code.

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long creditCardNumber = 1234_5678_9012_3456L;
long socialSecurityNumber = 999_99_9999L;
float pi =  3.14_15F;
long hexBytes = 0xFF_EC_DE_5E;
long hexWords = 0xCAFE_BABE;
long maxLong = 0x7fff_ffff_ffff_ffffL;
byte nybbles = 0b0010_0101;
long bytes = 0b11010010_01101001_10010100_10010010;
Posted in Tools - Tagged

Java – part 3

Sep01
2011 Leave a Comment Written by Eliott

Literals

Notice that in the last post we didn’t have define the variable with “new” or similar? Well that’s because variable types are built into the language and so are automatically detected.

Integers

Generally you will only use the decimal system, however Java does allow the following:

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int decVal = 26; // The number 26, in decimal
int hexVal = 0x1a; // The number 26, in hexadecimal
int binVal = 0b11010; // The number 26, in binary

Float and Double

A floating-point literal is of type float if it ends with the letter F or f; otherwise its type is double and it can optionally end with the letter D or d.

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double d1 = 123.4;
double d2 = 1.234e2; // same value as d1, but in scientific notation
float f1  = 123.4f;

String and Char

Literals of types char and String may contain any Unicode (UTF-16) characters as long as your editor and system can read them. It also understands many escaped characters such as:

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\b (backspace), \t (tab), \n (line feed), \f (form feed), \r (carriage return), \" (double quote), \' (single quote), and \\ (backslash).
Posted in Tools - Tagged

Java – part 2

Aug30
2011 Leave a Comment Written by Eliott

Variables

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String name = "Eliott";
int value = 5
char letter = 'e'
boolean response = true

And so on…
Here is the pretty much full list:

Data Type
byte
short
int
long
float
double
char
String
boolean

Posted in Tutorials - Tagged
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