mirror of git://gcc.gnu.org/git/gcc.git
98 lines
4.3 KiB
Java
98 lines
4.3 KiB
Java
/* Comparable.java -- Interface for comparaing objects to obtain an ordering
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Copyright (C) 1998, 1999, 2001, 2002 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.lang;
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/**
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* Interface for objects that can be ordering among other objects. The
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* ordering can be <em>total</em>, such that two objects only compare equal
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* if they are also equal by the equals method, or <em>partial</em> such
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* that this is not necessarily true. For example, a case-sensitive
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* dictionary order comparison of Strings is total, but if it is
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* case-insensitive it is partial, because "abc" and "ABC" compare as
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* equal even though "abc".equals("ABC") returns false. However, if you use
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* a partial ordering, it is a good idea to document your class as
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* "inconsistent with equals", because the behavior of your class in a
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* SortedMap will be different than in a HashMap.
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*
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* <p>Lists, arrays, and sets of objects that implement this interface can
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* be sorted automatically, without the need for an explicit
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* {@link Comparator}. Note that <code>e1.compareTo(null)</code> should
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* throw an Exception; as should comparison between incompatible classes.
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*
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* @author Geoff Berry
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* @author Warren Levy <warrenl@cygnus.com>
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* @see Comparator
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* @see Collections#sort(List)
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* @see Arrays#sort(Object[])
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* @see SortedSet
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* @see SortedMap
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* @see TreeSet
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* @see TreeMap
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* @since 1.2
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* @status updated to 1.4
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*/
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public interface Comparable
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{
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/**
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* Compares this object with another, and returns a numerical result based
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* on the comparison. If the result is negative, this object sorts less
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* than the other; if 0, the two are equal, and if positive, this object
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* sorts greater than the other. To translate this into boolean, simply
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* perform <code>o1.compareTo(o2) <em><op></em> 0</code>, where op
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* is one of <, <=, =, !=, >, or >=.
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*
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* <p>You must make sure that the comparison is mutual, ie.
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* <code>sgn(x.compareTo(y)) == -sgn(y.compareTo(x))</code> (where sgn() is
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* defined as -1, 0, or 1 based on the sign). This includes throwing an
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* exception in either direction if the two are not comparable; hence,
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* <code>compareTo(null)</code> should always throw an Exception.
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*
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* <p>You should also ensure transitivity, in two forms:
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* <code>x.compareTo(y) > 0 && y.compareTo(z) > 0</code> implies
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* <code>x.compareTo(z) > 0</code>; and <code>x.compareTo(y) == 0</code>
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* implies <code>x.compareTo(z) == y.compareTo(z)</code>.
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*
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* @param o the object to be compared
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* @return an integer describing the comparison
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* @throws NullPointerException if o is null
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* @throws ClassCastException if o cannot be compared
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*/
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int compareTo(Object o);
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}
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