mirror of
git://gcc.gnu.org/git/gcc.git
synced 2024-12-28 03:44:41 +08:00
120 lines
4.9 KiB
Java
120 lines
4.9 KiB
Java
/* Comparator.java -- Interface for objects that specify an ordering
|
|
Copyright (C) 1998, 2001 Free Software Foundation, Inc.
|
|
|
|
This file is part of GNU Classpath.
|
|
|
|
GNU Classpath 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 2, or (at your option)
|
|
any later version.
|
|
|
|
GNU Classpath 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.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with GNU Classpath; see the file COPYING. If not, write to the
|
|
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
|
|
02111-1307 USA.
|
|
|
|
Linking this library statically or dynamically with other modules is
|
|
making a combined work based on this library. Thus, the terms and
|
|
conditions of the GNU General Public License cover the whole
|
|
combination.
|
|
|
|
As a special exception, the copyright holders of this library give you
|
|
permission to link this library with independent modules to produce an
|
|
executable, regardless of the license terms of these independent
|
|
modules, and to copy and distribute the resulting executable under
|
|
terms of your choice, provided that you also meet, for each linked
|
|
independent module, the terms and conditions of the license of that
|
|
module. An independent module is a module which is not derived from
|
|
or based on this library. If you modify this library, you may extend
|
|
this exception to your version of the library, but you are not
|
|
obligated to do so. If you do not wish to do so, delete this
|
|
exception statement from your version. */
|
|
|
|
|
|
package java.util;
|
|
|
|
/**
|
|
* Interface for objects that specify an ordering between objects. The ordering
|
|
* should be <em>total</em>, such that any two objects of the correct type
|
|
* can be compared, and the comparison is reflexive, anti-symmetric, and
|
|
* transitive. It is also recommended that the comparator be <em>consistent
|
|
* with equals</em>, although this is not a strict requirement. A relation
|
|
* is consistent with equals if these two statements always have the same
|
|
* results (if no exceptions occur):<br>
|
|
* <code>compare((Object) e1, (Object) e2) == 0</code> and
|
|
* <code>e1.equals((Object) e2)</code><br>
|
|
* Comparators that violate consistency with equals may cause strange behavior
|
|
* in sorted lists and sets. For example, a case-sensitive dictionary order
|
|
* comparison of Strings is consistent with equals, but if it is
|
|
* case-insensitive it is not, because "abc" and "ABC" compare as equal even
|
|
* though "abc".equals("ABC") returns false.
|
|
* <P>
|
|
* In general, Comparators should be Serializable, because when they are passed
|
|
* to Serializable data structures such as SortedMap or SortedSet, the entire
|
|
* data structure will only serialize correctly if the comparator is
|
|
* Serializable.
|
|
*
|
|
* @author Original author unknown
|
|
* @author Eric Blake <ebb9@email.byu.edu>
|
|
* @see Comparable
|
|
* @see TreeMap
|
|
* @see TreeSet
|
|
* @see SortedMap
|
|
* @see SortedSet
|
|
* @see Arrays#sort(Object[], Comparator)
|
|
* @see java.io.Serializable
|
|
* @since 1.2
|
|
* @status updated to 1.4
|
|
*/
|
|
public interface Comparator
|
|
{
|
|
/**
|
|
* Return an integer that is negative, zero or positive depending on whether
|
|
* the first argument is less than, equal to or greater than the second
|
|
* according to this ordering. This method should obey the following
|
|
* contract:
|
|
* <ul>
|
|
* <li>if compare(a, b) < 0 then compare(b, a) > 0</li>
|
|
* <li>if compare(a, b) throws an exception, so does compare(b, a)</li>
|
|
* <li>if compare(a, b) < 0 and compare(b, c) < 0 then compare(a, c)
|
|
* < 0</li>
|
|
* <li>if compare(a, b) == 0 then compare(a, c) and compare(b, c) must
|
|
* have the same sign</li
|
|
* </ul>
|
|
* To be consistent with equals, the following additional constraint is
|
|
* in place:
|
|
* <ul>
|
|
* <li>if a.equals(b) or both a and b are null, then
|
|
* compare(a, b) == 0.</li>
|
|
* </ul><p>
|
|
*
|
|
* Although it is permissible for a comparator to provide an order
|
|
* inconsistent with equals, that should be documented.
|
|
*
|
|
* @param o1 the first object
|
|
* @param o2 the second object
|
|
* @return the comparison
|
|
* @throws ClassCastException if the elements are not of types that can be
|
|
* compared by this ordering.
|
|
*/
|
|
int compare(Object o1, Object o2);
|
|
|
|
/**
|
|
* Return true if the object is equal to this object. To be
|
|
* considered equal, the argument object must satisfy the constraints
|
|
* of <code>Object.equals()</code>, be a Comparator, and impose the
|
|
* same ordering as this Comparator. The default implementation
|
|
* inherited from Object is usually adequate.
|
|
*
|
|
* @param obj The object
|
|
* @return true if it is a Comparator that imposes the same order
|
|
* @see Object#equals(Object)
|
|
*/
|
|
boolean equals(Object obj);
|
|
}
|