1/*
2 *  Licensed to the Apache Software Foundation (ASF) under one or more
3 *  contributor license agreements.  See the NOTICE file distributed with
4 *  this work for additional information regarding copyright ownership.
5 *  The ASF licenses this file to You under the Apache License, Version 2.0
6 *  (the "License"); you may not use this file except in compliance with
7 *  the License.  You may obtain a copy of the License at
8 *
9 *     http://www.apache.org/licenses/LICENSE-2.0
10 *
11 *  Unless required by applicable law or agreed to in writing, software
12 *  distributed under the License is distributed on an "AS IS" BASIS,
13 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 *  See the License for the specific language governing permissions and
15 *  limitations under the License.
16 */
17
18package java.lang;
19
20/**
21 * This interface should be implemented by all classes that wish to define a
22 * <em>natural order</em> of their instances.
23 * {@link java.util.Collections#sort} and {@code java.util.Arrays#sort} can then
24 * be used to automatically sort lists of classes that implement this interface.
25 * <p>
26 * The order rule must be both transitive (if {@code x.compareTo(y) < 0} and
27 * {@code y.compareTo(z) < 0}, then {@code x.compareTo(z) < 0} must hold) and
28 * invertible (the sign of the result of x.compareTo(y) must be equal to the
29 * negation of the sign of the result of y.compareTo(x) for all combinations of
30 * x and y).
31 * <p>
32 * In addition, it is recommended (but not required) that if and only if the
33 * result of x.compareTo(y) is zero, then the result of x.equals(y) should be
34 * {@code true}.
35 */
36public interface Comparable<T> {
37
38    /**
39     * Compares this object to the specified object to determine their relative
40     * order.
41     *
42     * @param another
43     *            the object to compare to this instance.
44     * @return a negative integer if this instance is less than {@code another};
45     *         a positive integer if this instance is greater than
46     *         {@code another}; 0 if this instance has the same order as
47     *         {@code another}.
48     * @throws ClassCastException
49     *             if {@code another} cannot be converted into something
50     *             comparable to {@code this} instance.
51     */
52    int compareTo(T another);
53}
54