1 /*
2 * Copyright (c) 1997, 2007, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
81 * relation defined by the objects' {@link Object#equals(Object)
82 * equals(Object)} method(s):<pre>
83 * {(x, y) such that x.equals(y)}. </pre>
84 *
85 * <p>Unlike {@code Comparable}, a comparator may optionally permit
86 * comparison of null arguments, while maintaining the requirements for
87 * an equivalence relation.
88 *
89 * <p>This interface is a member of the
90 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
91 * Java Collections Framework</a>.
92 *
93 * @param <T> the type of objects that may be compared by this comparator
94 *
95 * @author Josh Bloch
96 * @author Neal Gafter
97 * @see Comparable
98 * @see java.io.Serializable
99 * @since 1.2
100 */
101
102 public interface Comparator<T> {
103 /**
104 * Compares its two arguments for order. Returns a negative integer,
105 * zero, or a positive integer as the first argument is less than, equal
106 * to, or greater than the second.<p>
107 *
108 * In the foregoing description, the notation
109 * <tt>sgn(</tt><i>expression</i><tt>)</tt> designates the mathematical
110 * <i>signum</i> function, which is defined to return one of <tt>-1</tt>,
111 * <tt>0</tt>, or <tt>1</tt> according to whether the value of
112 * <i>expression</i> is negative, zero or positive.<p>
113 *
114 * The implementor must ensure that <tt>sgn(compare(x, y)) ==
115 * -sgn(compare(y, x))</tt> for all <tt>x</tt> and <tt>y</tt>. (This
116 * implies that <tt>compare(x, y)</tt> must throw an exception if and only
117 * if <tt>compare(y, x)</tt> throws an exception.)<p>
118 *
119 * The implementor must also ensure that the relation is transitive:
120 * <tt>((compare(x, y)>0) && (compare(y, z)>0))</tt> implies
121 * <tt>compare(x, z)>0</tt>.<p>
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1 /*
2 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
81 * relation defined by the objects' {@link Object#equals(Object)
82 * equals(Object)} method(s):<pre>
83 * {(x, y) such that x.equals(y)}. </pre>
84 *
85 * <p>Unlike {@code Comparable}, a comparator may optionally permit
86 * comparison of null arguments, while maintaining the requirements for
87 * an equivalence relation.
88 *
89 * <p>This interface is a member of the
90 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
91 * Java Collections Framework</a>.
92 *
93 * @param <T> the type of objects that may be compared by this comparator
94 *
95 * @author Josh Bloch
96 * @author Neal Gafter
97 * @see Comparable
98 * @see java.io.Serializable
99 * @since 1.2
100 */
101 @FunctionalInterface
102 public interface Comparator<T> {
103 /**
104 * Compares its two arguments for order. Returns a negative integer,
105 * zero, or a positive integer as the first argument is less than, equal
106 * to, or greater than the second.<p>
107 *
108 * In the foregoing description, the notation
109 * <tt>sgn(</tt><i>expression</i><tt>)</tt> designates the mathematical
110 * <i>signum</i> function, which is defined to return one of <tt>-1</tt>,
111 * <tt>0</tt>, or <tt>1</tt> according to whether the value of
112 * <i>expression</i> is negative, zero or positive.<p>
113 *
114 * The implementor must ensure that <tt>sgn(compare(x, y)) ==
115 * -sgn(compare(y, x))</tt> for all <tt>x</tt> and <tt>y</tt>. (This
116 * implies that <tt>compare(x, y)</tt> must throw an exception if and only
117 * if <tt>compare(y, x)</tt> throws an exception.)<p>
118 *
119 * The implementor must also ensure that the relation is transitive:
120 * <tt>((compare(x, y)>0) && (compare(y, z)>0))</tt> implies
121 * <tt>compare(x, z)>0</tt>.<p>
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