JAVA Help		    Thu Sep 28 19:35:45 EDT 2006

API Documentation
--- ------------

JAVA API documentation is usually available on-line
during a formal contest.  The command to access it is:

	javahelp

In a formal contest, you should NOT use other means to
access such documentation, as using the internet is a
violation of formal contest rules.


Program Structure
------- ---------

The following is a suitable structure for a program that
solves the problem named PPPP:


    import java.io.*;
    import java.util.StringTokenizer;

    public class PPPP {

	public static boolean debug;

	public static void dprintln ( String s )
	{
	    if ( debug ) System.out.println ( s );
	}

	public static void main (String[] args)
		throws IOException
	{

	    debug = ( args.length > 0 );

	    BufferedReader reader
	       = new BufferedReader
		     ( new InputStreamReader
			   ( System.in ) );

	    while ( true )
	    {

		String line = reader.readLine();
		if ( line == null ) break;

		StringTokenizer tokenizer
		    = new StringTokenizer ( line );
		. . .

		dprintln ( . . . );

		System.out.println ( . . . );
	    }
	}
    }

Some parts of this structure are described below, and
examples are given in demos/count/count1.java and
demos/javaio/javaio.java.


Debugging
---------

In the above program structure, debugging is turned on
if the program is called with any arguments (the main
function args is of non-zero length).  In this case
the dprintln function prints, and in the opposite case,
where the program is called with no arguments, dprintln
does nothing.


Input
-----

Line oriented input is best done with

	java.io.BufferedReader.readLine
	java.util.StringTokenizer.getToken

An example is in the count1.java demo.  When using this
method, strings returned by getToken may have to be
converted to numbers.  This can be done by code such as

	String s = ...;
	int i = Integer.parseInt ( s );
	long l = Long.parseLong ( s );
	double d = Double.parseDouble ( s );

If line ends are to be treated just like space charac-
ters, using

	java.io.StreamTokenizer
	
is a good idea.  An example is in the javaio.java demo.


Output
------

Output of floating point numbers with a specified number
of decimal places is done with

	java.text.DecimalFormat

See the javaio.java demo.  It is important in some
contests to use a DecimalFormat object created with the
ENGLISH Locale.

Numbers that are output should NEVER have commas in
them, unless the problem specifically states otherwise.
This can be a problem if one uses NumberFormat.get_
instance and then fails to use applyPattern (see the
javaio.java demo).

String and free format number output examples merely use

	System.out.println
	
and are given in the count1.java an javaio.java demos.


Crashes
-------

It is fairly common for JAVA programs which run well for
the contestant to crash when run by the judge.  The
usual cause is judge's input data that triggers an ex-
ception not observed with contestant input data.
Examples are when an out-of-range array index is used,
or the program one runs off the end of an input line
and calls getToken with no more tokens.  The best debug-
ging strategy is to try to find input data that breaks
the program.





File:		java
Author:		Bob Walton <walton@deas.harvard.edu>
Date:		See top of file.

The authors have placed this file in the public domain;
they make no warranty and accept no liability for this
file.

RCS Info (may not be true date or author):

    $Author: walton $
    $Date: 2006/09/28 23:37:30 $
    $RCSfile: java,v $
    $Revision: 1.7 $