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Types that extend and augment the Java Collections Framework.
/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2003-2004 The Apache Software Foundation. All rights
* reserved.
*
* 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.
*
* 3. The end-user documentation included with the redistribution, if
* any, must include the following acknowledgement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
*
* 4. The names "The Jakarta Project", "Commons", and "Apache Software
* Foundation" must not be used to endorse or promote products derived
* from this software without prior written permission. For written
* permission, please contact [email protected].
*
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* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* BooleanComparator
* that sorts false values before
* true values.
*
* Equivalent to {@link #BooleanComparator(boolean) BooleanComparator(false)}.
*/
public BooleanComparator() {
this(false);
}
/**
* Creates a BooleanComparator
* that sorts trueFirst values before
* !trueFirst values.
*
* @param trueFirst when true, sort
* true {@link Boolean}s before
* false {@link Boolean}s.
*/
public BooleanComparator(boolean trueFirst) {
this.trueFirst = trueFirst;
}
/**
* Compares two arbitrary Objects. When both arguments
* are {@link Boolean}, this method is equivalent to
* {@link #compare(Boolean,Boolean) compare((Boolean)o1,(Boolean)o2)}.
* When either argument is not a {@link Boolean}, this methods throws
* a {@link ClassCastException}.
*
* @throws ClassCastException when either argument is not
* a {@link Boolean}
*/
public int compare(Object o1, Object o2) {
return compare((Boolean)o1,(Boolean)o2);
}
/**
* Compares two non-null {@link Boolean}s
* according to the value of {@link #sortsTrueFirst}.
*
* @throws NullPointerException when either argument null
*/
public int compare(Boolean b1, Boolean b2) {
boolean v1 = b1.booleanValue();
boolean v2 = b2.booleanValue();
return (v1 ^ v2) ? ( (v1 ^ trueFirst) ? 1 : -1 ) : 0;
}
/**
* Implement a hash code for this comparator that is consistent with
* {@link #equals equals}.
*
* @return a hash code for this comparator.
*/
public int hashCode() {
int hash = "BooleanComparator".hashCode();
return trueFirst ? -1 * hash : hash;
}
/**
* Returns true iff that Object is
* is a {@link Comparator} whose ordering is known to be
* equivalent to mine.
*
* This implementation returns true
* iff that is a {@link BooleanComparator}
* whose {@link #sortsTrueFirst} value is equal to mine.
*/
public boolean equals(Object that) {
return (this == that) ||
((that instanceof BooleanComparator) &&
(this.trueFirst == ((BooleanComparator)that).trueFirst));
}
/**
* Returns true iff
* I sort true values before
* false values. In other words,
* returns true iff
* {@link #compare(Boolean,Boolean) compare(Boolean.FALSE,Boolean.TRUE)}
* returns a positive value.
*/
public boolean sortsTrueFirst() {
return trueFirst;
}
/**
* Returns a BooleanComparator instance that sorts
* true values before false values.
*
* Clients are encouraged to use the value returned from
* this method instead of constructing a new instance
* to reduce allocation and garbage collection overhead when
* multiple BooleanComparators may be used in the same
* virtual machine.
*/
public static BooleanComparator getTrueFirstComparator() {
return TRUE_FIRST;
}
/**
* Returns a BooleanComparator instance that sorts
* false values before true values.
*
* Clients are encouraged to use the value returned from
* this method instead of constructing a new instance
* to reduce allocation and garbage collection overhead when
* multiple BooleanComparators may be used in the same
* virtual machine.
*/
public static BooleanComparator getFalseFirstComparator() {
return FALSE_FIRST;
}
/**
* Returns a BooleanComparator instance that sorts
* trueFirst values before
* !trueFirst values.
*
* Clients are encouraged to use the value returned from
* this method instead of constructing a new instance
* to reduce allocation and garbage collection overhead when
* multiple BooleanComparators may be used in the same
* virtual machine.
*
* @param trueFirst when true, sort
* true {@link Boolean}s before
* false {@link Boolean}s.
* @return a cached BooleanComparator instance
*/
public static BooleanComparator getBooleanComparator(boolean trueFirst) {
return trueFirst ? TRUE_FIRST : FALSE_FIRST;
}
/** true iff true values sort before false values. */
private boolean trueFirst = false;
/** My static "true first" reference. */
private static final BooleanComparator TRUE_FIRST = new BooleanComparator(true);
/** My static "false first" reference. */
private static final BooleanComparator FALSE_FIRST = new BooleanComparator(false);
}