I used the following to convert my date:

package com.etechtips;

import java.util.Calendar;
import java.util.GregorianCalendar;

import javax.xml.datatype.DatatypeConfigurationException;
import javax.xml.datatype.DatatypeFactory;
import javax.xml.datatype.XMLGregorianCalendar;

public class UpdateDate {

	public static void main(String[] args) {
		XMLGregorianCalendar xgcstart;
		GregorianCalendar gc;
		int daycount = 0;
		if (args.length != 1)
		{
			System.out.println("Need to specify offset");
			System.exit(1);
		}

		daycount = Integer.parseInt(args[0]);

		// This will get the current date based on System time of an object
		gc = new GregorianCalendar();
		System.out.println("CURRENT:" + gc.toString());

		// This will offset the date by daycount days
		gc.add(Calendar.DATE, daycount);
		System.out.println("OFFSET: "+ gc.toString());

		try
		{
			// Now the XMLGregorianCalendar object has an
                        instance that is based on the time set in the gc object
			xgcstart = DatatypeFactory.newInstance().newXMLGregorianCalendar(gc);
		}
		catch(DatatypeConfigurationException dce)
		{
			dce.printStackTrace();
			System.exit(1);
		}

		// Code omitted
	}
}

Output:

CURRENT:java.util.GregorianCalendar[time=1321793315934,areFieldsSet=true,areAllFieldsSet=true,\
lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/Chicago",offset=-21600000,\
dstSavings=3600000,useDaylight=true,transitions=235,\
lastRule=java.util.SimpleTimeZone[id=America/Chicago,offset=-21600000,dstSavings=3600000,\
useDaylight=true,startYear=0,startMode=3,startMonth=2,startDay=8,startDayOfWeek=1,\
startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,endDayOfWeek=1,endTime=7200000,\
endTimeMode=0]],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,YEAR=2011,MONTH=10,\
WEEK_OF_YEAR=48,WEEK_OF_MONTH=4,DAY_OF_MONTH=20,DAY_OF_YEAR=324,DAY_OF_WEEK=1,DAY_OF_WEEK_IN_MONTH=3,\
AM_PM=0,HOUR=6,HOUR_OF_DAY=6,MINUTE=48,SECOND=35,MILLISECOND=934,ZONE_OFFSET=-21600000,\
DST_OFFSET=0]
OFFSET: java.util.GregorianCalendar[time=1321706915934,areFieldsSet=true,areAllFieldsSet=true,\
lenient=true,zone=sun.util.calendar.ZoneInfo[id="America/Chicago",offset=-21600000,\
dstSavings=3600000,useDaylight=true,transitions=235,lastRule=java.util.SimpleTimeZone[id=America/Chicago,\
offset=-21600000,dstSavings=3600000,useDaylight=true,startYear=0,startMode=3,startMonth=2,\
startDay=8,startDayOfWeek=1,startTime=7200000,startTimeMode=0,endMode=3,endMonth=10,endDay=1,\
endDayOfWeek=1,endTime=7200000,endTimeMode=0]],firstDayOfWeek=1,minimalDaysInFirstWeek=1,ERA=1,\
YEAR=2011,MONTH=10,WEEK_OF_YEAR=47,WEEK_OF_MONTH=3,DAY_OF_MONTH=19,DAY_OF_YEAR=323,\
DAY_OF_WEEK=7,DAY_OF_WEEK_IN_MONTH=3,AM_PM=0,HOUR=6,HOUR_OF_DAY=6,MINUTE=48,SECOND=35,\
MILLISECOND=934,ZONE_OFFSET=-21600000,DST_OFFSET=0]

The printouts above show the current date and the new date based on the offset. I made the day of the month bold in the printouts to show what the offset has updated the date. You could put a much larger offset than 1 and Calendar object will take care of updating the day of week, week of year and more. You will not need to deal with checking for leap year or dealing with updating all the month and years, this is all taken care of for you.

The following is the basic code to handle the command line arguments.

class CmdArgs
{

  public static void main(String[] args)
  {
      int argsize = args.length;
      String curarg;

      if (argsize > 0 )
      {

      }

      for(int i = 0; i < argsize; i++)
      {
          if (args[i].equals("--host")
          {
             args++;
             host = args[i];
           }
          else if (args[i].equals("--debug")
          {
               debug = 1;
          }
          else
          {
              System.out.println("Unknown option: " + args[i]);
              System.exit(1);
          }
       }

   }
}

The bat file for Dos/Windows might look like this:

@echo off

java -cp c:\javabin;somejar.jar  com.etechtips.CmdArgs %*

The shell based file might look like:

java -cp /home/ecdown/javabin:somejar.jar com.etechtips.CmdArgs $*

C

#include
int main()
{
printf("Hello World!");
}

C++

#include
int main()
{
cout << "Hello World!" << endl;
}

C#

public class HelloWorld
  public static void Main()
  {
    System.Console.WriteLine("Hello World!");
  }

Java

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

SHELL

echo "Hello World"

Python

print "Hello World!\n"

Ruby

puts "Hello World!"

Perl

print "Hello World!\n";

PHP

  <?php
    print "Hello World!";
  ?>

This is the simplest form of Hello World for most of these languages.

This had to do with my JAVA_HOME not pointing to a Java JDK.

So if you download a JDK and update your JAVA_HOME environment variable to point to that directory, ant should run happily.

In BASH:
export JAVA_HOME=/path/to/jdk

IN DOS:
set JAVA_HOME=c:\PATH\to\jdk

Compile:

$> javac LottoMain.java

Run:

$> java LottoMain

Exception in thread “main” java.lang.NoClassDefFoundError: LottoMain
Caused by: java.lang.ClassNotFoundException: LottoMain
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:319)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:264)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:332)
Could not find the main class: LottoMain. Program will exit.

The compile line completed without errrors and the LottoMain.class file was there, but
what I didn’t know was that I no longer had the current directory “.” in my CLASSPATH variable.

After adding “.” to my CLASSPATH variable the run command gave me what I was expecting.

Run:

$> java LottoMain

Hello Eric!

Updating the CLASSPATH variable in Bash:
in my home directory/.bashrc file

export CLASSPATH=$CLASSPATH:.

Using Swing Components: Examples

It has code examples and can really get you started on the road to a Java GUI interface.

import java.awt.*;
import java.swing.*;

class FirstWindow
{

  public static void main(String[] args)
  {
      //Create Window object and set title bar text
      JFrame frame = new frame("First Window");

      // Set the Default operation when you close the window
      // This exits the program on closing the window
      // The default behavior is to HIDE_ON_CLOSE
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

      // Now we need to Display the window
      // The null argument will place the element in the center of the screen.
      frame.setLocationRelativeTo(null);
      frame.pack();
      frame.setVisible(true);
   }
}

This is enough to display a simple window, but it will probably not have any useful size associated with it and it does not do anything.

The next step will be to add some useful widgets and eventually functionality to make the window useful.

Helpful info:
Java: Great link to Swing Examples

Example:

MAVEN_OPTS=-Xmx1024

Depending on what environment you are in, you will need to set this variable.

This will give the JVM more 1024 megs to work with and you can customize the number to fit your needs.

Here is a snippet of code to show a simple way to format a number with a fixed number of digits.

import java.text.DecimalFormat;

class TestEncoder
{
        public static void main(String[] args)
        {
                // This program expects one integer
                // argument and places it in the num1
                // variable. This program is not very
                // robust as to watch for no arguments
                // or to check if the argument is not
                // an integer.
                String num1 = args[0];
                String output;

                // This creates the Decimal Format instance
                // and assigns the formatting that we want
                // to use, in this case three characters .
                DecimalFormat dfmt =
                             new DecimalFormat("000");

                // This does the work of formatting the number
                // passed in on the command line to be at least
                // three digits.
                output = dfmt.format(new Integer(num1));

                // This just displays the results of the
                // dfmt.format(new Integer(num1)) command.
                System.out.println("Output: " + output);
}
}

The Decimal format allows for many more formatting options for numbers.

Make sure to look a the API docs for the version of Java that you are using:

http://java.sun.com/j2se/1.5.0/docs/api/java/text/DecimalFormat.html