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8187443: Forest Consolidation: Move files to unified layout
Reviewed-by: darcy, ihse
This commit is contained in:
Erik Joelsson
parent
270fe13182
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3789983e89
56923 changed files with 3 additions and 15727 deletions
138
src/java.base/share/classes/java/lang/Comparable.java
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138
src/java.base/share/classes/java/lang/Comparable.java
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/*
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* Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.lang;
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import java.util.*;
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/**
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* This interface imposes a total ordering on the objects of each class that
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* implements it. This ordering is referred to as the class's <i>natural
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* ordering</i>, and the class's {@code compareTo} method is referred to as
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* its <i>natural comparison method</i>.<p>
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*
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* Lists (and arrays) of objects that implement this interface can be sorted
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* automatically by {@link Collections#sort(List) Collections.sort} (and
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* {@link Arrays#sort(Object[]) Arrays.sort}). Objects that implement this
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* interface can be used as keys in a {@linkplain SortedMap sorted map} or as
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* elements in a {@linkplain SortedSet sorted set}, without the need to
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* specify a {@linkplain Comparator comparator}.<p>
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*
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* The natural ordering for a class {@code C} is said to be <i>consistent
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* with equals</i> if and only if {@code e1.compareTo(e2) == 0} has
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* the same boolean value as {@code e1.equals(e2)} for every
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* {@code e1} and {@code e2} of class {@code C}. Note that {@code null}
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* is not an instance of any class, and {@code e.compareTo(null)} should
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* throw a {@code NullPointerException} even though {@code e.equals(null)}
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* returns {@code false}.<p>
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*
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* It is strongly recommended (though not required) that natural orderings be
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* consistent with equals. This is so because sorted sets (and sorted maps)
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* without explicit comparators behave "strangely" when they are used with
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* elements (or keys) whose natural ordering is inconsistent with equals. In
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* particular, such a sorted set (or sorted map) violates the general contract
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* for set (or map), which is defined in terms of the {@code equals}
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* method.<p>
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*
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* For example, if one adds two keys {@code a} and {@code b} such that
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* {@code (!a.equals(b) && a.compareTo(b) == 0)} to a sorted
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* set that does not use an explicit comparator, the second {@code add}
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* operation returns false (and the size of the sorted set does not increase)
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* because {@code a} and {@code b} are equivalent from the sorted set's
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* perspective.<p>
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*
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* Virtually all Java core classes that implement {@code Comparable} have natural
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* orderings that are consistent with equals. One exception is
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* {@code java.math.BigDecimal}, whose natural ordering equates
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* {@code BigDecimal} objects with equal values and different precisions
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* (such as 4.0 and 4.00).<p>
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*
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* For the mathematically inclined, the <i>relation</i> that defines
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* the natural ordering on a given class C is:<pre>{@code
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* {(x, y) such that x.compareTo(y) <= 0}.
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* }</pre> The <i>quotient</i> for this total order is: <pre>{@code
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* {(x, y) such that x.compareTo(y) == 0}.
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* }</pre>
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*
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* It follows immediately from the contract for {@code compareTo} that the
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* quotient is an <i>equivalence relation</i> on {@code C}, and that the
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* natural ordering is a <i>total order</i> on {@code C}. When we say that a
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* class's natural ordering is <i>consistent with equals</i>, we mean that the
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* quotient for the natural ordering is the equivalence relation defined by
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* the class's {@link Object#equals(Object) equals(Object)} method:<pre>
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* {(x, y) such that x.equals(y)}. </pre><p>
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*
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* This interface is a member of the
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* <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
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* Java Collections Framework</a>.
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*
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* @param <T> the type of objects that this object may be compared to
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*
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* @author Josh Bloch
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* @see java.util.Comparator
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* @since 1.2
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*/
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public interface Comparable<T> {
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/**
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* Compares this object with the specified object for order. Returns a
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* negative integer, zero, or a positive integer as this object is less
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* than, equal to, or greater than the specified object.
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*
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* <p>The implementor must ensure
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* {@code sgn(x.compareTo(y)) == -sgn(y.compareTo(x))}
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* for all {@code x} and {@code y}. (This
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* implies that {@code x.compareTo(y)} must throw an exception iff
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* {@code y.compareTo(x)} throws an exception.)
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*
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* <p>The implementor must also ensure that the relation is transitive:
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* {@code (x.compareTo(y) > 0 && y.compareTo(z) > 0)} implies
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* {@code x.compareTo(z) > 0}.
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*
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* <p>Finally, the implementor must ensure that {@code x.compareTo(y)==0}
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* implies that {@code sgn(x.compareTo(z)) == sgn(y.compareTo(z))}, for
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* all {@code z}.
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*
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* <p>It is strongly recommended, but <i>not</i> strictly required that
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* {@code (x.compareTo(y)==0) == (x.equals(y))}. Generally speaking, any
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* class that implements the {@code Comparable} interface and violates
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* this condition should clearly indicate this fact. The recommended
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* language is "Note: this class has a natural ordering that is
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* inconsistent with equals."
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*
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* <p>In the foregoing description, the notation
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* {@code sgn(}<i>expression</i>{@code )} designates the mathematical
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* <i>signum</i> function, which is defined to return one of {@code -1},
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* {@code 0}, or {@code 1} according to whether the value of
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* <i>expression</i> is negative, zero, or positive, respectively.
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*
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* @param o the object to be compared.
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* @return a negative integer, zero, or a positive integer as this object
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* is less than, equal to, or greater than the specified object.
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*
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* @throws NullPointerException if the specified object is null
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* @throws ClassCastException if the specified object's type prevents it
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* from being compared to this object.
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*/
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public int compareTo(T o);
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}
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