To posting code in wordpress.com just wrap your code in these tags:

[sourcecode language=”java”]
your code here
[/sourcecode]

The language parameter controls how the code is syntax highlighted. The following languages are supported:

  • actionscript3
  • bash
  • coldfusion
  • cpp
  • csharp
  • css
  • delphi
  • erlang
  • fsharp
  • diff
  • groovy
  • html
  • javascript
  • java
  • javafx
  • matlab (keywords only)
  • objc
  • perl
  • php
  • text
  • powershell
  • python
  • r
  • ruby
  • scala
  • sql
  • vb
  • xml

If the language parameter is not set, it will default to “text” (no syntax highlighting).

Code in between the source code tags will automatically be encoded for display, you don’t need to worry about HTML entities or anything.

Configuration Parameters

The shortcodes also accept a variety of configuration parameters that you may use to customize the output. All are completely optional.

  • autolinks (true/false) — Makes all URLs in your posted code clickable. Defaults to true.
  • collapse (true/false) — If true, the code box will be collapsed when the page loads, requiring the visitor to click to expand it. Good for large code posts. Defaults to false.
  • firstline (number) — Use this to change what number the line numbering starts at. It defaults to 1.
  • gutter (true/false) — If false, the line numbering on the left side will be hidden. Defaults to true.
  • highlight (comma-seperated list of numbers) — You can list the line numbers you want to be highlighted. For example “4,7,19″.
  • htmlscript (true/false) — If true, any HTML/XML in your code will be highlighted. This is useful when you are mixing code into HTML, such as PHP inside of HTML. Defaults to false and will only work with certain code languages.
  • light (true/false) — If true, the gutter (line numbering) and toolbar (see below) will be hidden. This is helpful when posting only one or two lines of code. Defaults to false.
  • padlinenumbers (true/false/integer) — Allows you to control the line number padding. true will result in automatic padding, false will result in no padding, and entering a number will force a specific amount of padding.
  • toolbar (true/false) — If false, the toolbar containing the helpful buttons that appears when you hover over the code will not be shown. Defaults to true.
  • wraplines (true/false) — If false, line wrapping will be disabled. This will cause a horizontal scrollbar to appear for long lines of code.

Example for preview to posting is:

package number;

import java.io.BufferedReader;
import java.io.InputStreamReader;

import javax.swing.JOptionPane;

public class Prime {
public static void main(String[] args) throws Exception{
int i;
System.out.println("Enter number:");

String numString = JOptionPane.showInputDialog("Enter max number who consist prime number: ");
int num =Integer.parseInt(numString) ;
System.out.println("Prime number: ");
for (i=1; i < num; i++ ){
int j;
for (j=2; jint n = i%j;
if (n==0){
break;
}
}
if(i == j){
System.out.print("  "+i);
}
}
}
}

 

credit: http://en.support.wordpress.com/code/posting-source-code/