Mega Code Archive
Demonstrates the use of final collections
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/*
* file: FinalCollections.java
* package: oreilly.hcj.finalstory
*
* This software is granted under the terms of the Common Public License,
* CPL, which may be found at the following URL:
* http://www-124.ibm.com/developerworks/oss/CPLv1.0.htm
*
* Copyright(c) 2003-2005 by the authors indicated in the @author tags.
* All Rights are Reserved by the various authors.
*
########## DO NOT EDIT ABOVE THIS LINE ########## */
import java.awt.Color;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
/**
* Demonstrates the use of final collections.
*
* @author <a href=mailto:kraythe@arcor.de>Robert Simmons jr. (kraythe)</a>
* @version $Revision: 1.3 $
*/
public class FinalCollections {
/**
* Main method for demonstration.
*
* @param args
* Command line arguments.
*/
public static final void main(final String[] args) {
Rainbow.someMethod();
System.out.println("------------------");
try {
RainbowBetter.someMethod();
} catch (final UnsupportedOperationException ex) {
ex.printStackTrace(System.out);
System.out.println("Told you it would exception =)");
}
}
/**
* A class that demonstrates the rainbow.
*
* @author <a href=mailto:kraythe@arcor.de>Robert Simmons jr. (kraythe)</a>
* @version $Revision: 1.3 $
*/
public static class Rainbow {
/** The set of valid colors of the rainbow. */
public static final Set VALID_COLORS;
static {
VALID_COLORS = new HashSet();
VALID_COLORS.add(Color.red);
VALID_COLORS.add(Color.orange);
VALID_COLORS.add(Color.yellow);
VALID_COLORS.add(Color.green);
VALID_COLORS.add(Color.blue);
VALID_COLORS.add(Color.decode("#4B0082")); // indigo
VALID_COLORS.add(Color.decode("#8A2BE2")); // violet
}
/**
* A demo method.
*/
public static final void someMethod() {
Set colors = Rainbow.VALID_COLORS;
colors.add(Color.black); // <= logic error but allowed by compiler
System.out.println(colors);
}
}
/**
* A better version of the rainbow class using an unmodifiable set.
*
* @author <a href=mailto:kraythe@arcor.de>Robert Simmons jr. (kraythe)</a>
* @version $Revision: 1.3 $
*/
public static class RainbowBetter {
/** The valid colors of the rainbow. */
public static final Set VALID_COLORS;
static {
Set temp = new HashSet();
temp.add(Color.red);
temp.add(Color.orange);
temp.add(Color.yellow);
temp.add(Color.green);
temp.add(Color.blue);
temp.add(Color.decode("#4B0082")); // indigo
temp.add(Color.decode("#8A2BE2")); // violet
VALID_COLORS = Collections.unmodifiableSet(temp);
}
/**
* Some demo method.
*/
public static final void someMethod() {
Set colors = RainbowBetter.VALID_COLORS;
colors.add(Color.black); // <= exception here
System.out.println(colors);
}
}
}
/* ########## End of File ########## */
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