Java/Development Class/Class Path

getClass().getResourceAsStream

 // This example is from the book _Java AWT Reference_ by John Zukowski.
// Written by John Zukowski.  Copyright (c) 1997 O"Reilly & Associates.
// You may study, use, modify, and distribute this example for any purpose.
// This example is provided WITHOUT WARRANTY either expressed or
import java.applet.Applet;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Properties;
public class Prop11 extends Applet {
  Image im;
  Font f;
  String msg;
  public void paint(Graphics g) {
    g.setFont(f);
    if (im != null)
      g.drawImage(im, 50, 100, this);
    if (msg != null)
      g.drawString(msg, 50, 50);
  }
  public void init() {
    InputStream is = getClass().getResourceAsStream("prop11.list");
    Properties p = new Properties();
    try {
      p.load(is);
      f = Font.decode(p.getProperty("MyProg.font"));
      msg = p.getProperty("MyProg.message");
      String name = p.getProperty("MyProg.image");
      URL url = getClass().getResource(name);
      im = getImage(url);
    } catch (IOException e) {
      System.out.println("error loading props...");
    }
  }
}
File: prop11.list
MyProg.font.size=20
MyProg.font.type=italic-bold
MyProg.font.name=Helvetica
MyProg.message=Hello World

Load resource file: absolute from the classpath

import java.io.IOException;
import java.net.URL;
public class Main {
  public static void main(String[] args) throws IOException {
    // absolute from the classpath
    URL url = Main.class.getResource("/mypackage/foo.txt");
  }
}

Load resource file: relative to the class location

import java.io.IOException;
import java.net.URL;
public class Main {
  public static void main(String[] args) throws IOException {
    // relative to the class location
    URL url = Main.class.getResource("foo.txt");
  }
}

relative document loading in classpath

import java.io.IOException;
import java.net.URL;
public class Main {
  public static void main(String[] args) throws IOException {
    // relative document
    URL url = Main.class.getResource("docs/bar.txt");
  }
}

Try adding one or more item(s) to class path

/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.ru/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS""
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * Java, the Duke mascot, and all variants of Sun"s Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun"s, and James Gosling"s,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */
import java.util.Properties;
/**
 * Try adding one or more item(s) to class path.
 */
public class SysPropSet {
  static Properties p = System.getProperties();
  public static void main(String[] argv) {
    System.out.println("System Properties:");
    System.out.println("java.class.path now = " + getClassPath());
    p.setProperty("java.class.path", getClassPath() + ";"
        + "C:/jdk1.2/lib/tools.jar");
    System.out.println("java.class.path now = " + getClassPath());
    try {
      Class.forName("sun.tools.javap.JavaP");
    } catch (Exception e) {
      System.err.println(e);
      return;
    }
    System.out.println("Got it!!");
  }
  static String getClassPath() {
    return p.getProperty("java.class.path", null);
  }
}