pj2/lib/edu/rit/io/Stdio.java

//******************************************************************************
//
// File:    Stdio.java
// Package: edu.rit.io
// Unit:    Class edu.rit.io.Stdio
//
// This Java source file is copyright (C) 2013 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java 2 Library ("PJ2"). PJ2 is
// free software; you can redistribute it and/or modify it under the terms of
// the GNU General Public License as published by the Free Software Foundation;
// either version 3 of the License, or (at your option) any later version.
//
// PJ2 is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************

package edu.rit.io;

import java.io.InputStream;
import java.io.PrintStream;

/**
 * Class Stdio provides standard I/O streams that can be redirected on a
 * per-thread basis.
 *
 * @author  Alan Kaminsky
 * @version 23-Jun-2013
 */
public class Stdio
	{

// Prevent construction.

	private Stdio()
		{
		}

// Hidden data members.

	private static ThreadLocal<InputStream> in =
		new ThreadLocal<InputStream>()
			{
			protected InputStream initialValue()
				{
				return System.in;
				}
			};

	private static ThreadLocal<PrintStream> out =
		new ThreadLocal<PrintStream>()
			{
			protected PrintStream initialValue()
				{
				return System.out;
				}
			};

	private static ThreadLocal<PrintStream> err =
		new ThreadLocal<PrintStream>()
			{
			protected PrintStream initialValue()
				{
				return System.err;
				}
			};


// Exported operations.

	/**
	 * Get the standard input stream for the calling thread.
	 *
	 * @return  Standard input stream.
	 */
	public static InputStream in()
		{
		return in.get();
		}

	/**
	 * Get the standard output stream for the calling thread.
	 *
	 * @return  Standard output stream.
	 */
	public static PrintStream out()
		{
		return out.get();
		}

	/**
	 * Get the standard error stream for the calling thread.
	 *
	 * @return  Standard error stream.
	 */
	public static PrintStream err()
		{
		return err.get();
		}

	/**
	 * Set the standard input stream for the calling thread. If not set, the
	 * default is <TT>System.in</TT>.
	 *
	 * @param  stream  Standard input stream.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>stream</TT> is null.
	 */
	public static void in
		(InputStream stream)
		{
		if (stream == null)
			{
			throw new NullPointerException ("Stdio.in(): stream is null");
			}
		in.set (stream);
		}

	/**
	 * Set the standard output stream for the calling thread. If not set, the
	 * default is <TT>System.out</TT>.
	 *
	 * @param  stream  Standard output stream.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>stream</TT> is null.
	 */
	public static void out
		(PrintStream stream)
		{
		if (stream == null)
			{
			throw new NullPointerException ("Stdio.out(): stream is null");
			}
		out.set (stream);
		}

	/**
	 * Set the standard error stream for the calling thread. If not set, the
	 * default is <TT>System.err</TT>.
	 *
	 * @param  stream  Standard error stream.
	 *
	 * @exception  NullPointerException
	 *     (unchecked exception) Thrown if <TT>stream</TT> is null.
	 */
	public static void err
		(PrintStream stream)
		{
		if (stream == null)
			{
			throw new NullPointerException ("Stdio.err(): stream is null");
			}
		err.set (stream);
		}

	}