java/util/KeyValueHolder.java

/*
 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.util;

/**
 * An immutable container for a key and a value, suitable for use
 * in creating and populating {@code Map} instances.
 *
 * <p>This is a <a href="../lang/doc-files/ValueBased.html">value-based</a>
 * class; use of identity-sensitive operations (including reference equality
 * ({@code ==}), identity hash code, or synchronization) on instances of
 * {@code KeyValueHolder} may have unpredictable results and should be avoided.
 *
 * @apiNote
 * This class is not public. Instances can be created using the
 * {@link Map#entry Map.entry(k, v)} factory method, which is public.
 *
 * <p>This class differs from AbstractMap.SimpleImmutableEntry in the following ways:
 * it is not serializable, it is final, and its key and value must be non-null.
 *
 * @param <K> the key type
 * @param <V> the value type
 *
 * @see Map#ofEntries Map.ofEntries()
 * @since 9
 */
final class KeyValueHolder<K,V> implements Map.Entry<K,V> {
    final K key;
    final V value;

    KeyValueHolder(K k, V v) {
        key = Objects.requireNonNull(k);
        value = Objects.requireNonNull(v);
    }

    /**
     * Gets the key from this holder.
     *
     * @return the key
     */
    @Override
    public K getKey() {
        return key;
    }

    /**
     * Gets the value from this holder.
     *
     * @return the value
     */
    @Override
    public V getValue() {
        return value;
    }

    /**
     * Throws {@link UnsupportedOperationException}.
     *
     * @param value ignored
     * @return never returns normally
     */
    @Override
    public V setValue(V value) {
        throw new UnsupportedOperationException("not supported");
    }

    /**
     * Compares the specified object with this entry for equality.
     * Returns {@code true} if the given object is also a map entry and
     * the two entries' keys and values are equal. Note that key and
     * value are non-null, so equals() can be called safely on them.
     */
    @Override
    public boolean equals(Object o) {
        if (!(o instanceof Map.Entry))
            return false;
        Map.Entry<?,?> e = (Map.Entry<?,?>)o;
        return key.equals(e.getKey()) && value.equals(e.getValue());
    }

    /**
     * Returns the hash code value for this map entry. The hash code
     * is {@code key.hashCode() ^ value.hashCode()}. Note that key and
     * value are non-null, so hashCode() can be called safely on them.
     */
    @Override
    public int hashCode() {
        return key.hashCode() ^ value.hashCode();
    }

    /**
     * Returns a String representation of this map entry.  This
     * implementation returns the string representation of this
     * entry's key followed by the equals character ("{@code =}")
     * followed by the string representation of this entry's value.
     *
     * @return a String representation of this map entry
     */
    @Override
    public String toString() {
        return key + "=" + value;
    }
}
Revision:	1.2
Committed:	Sat Mar 26 19:25:33 2016 UTC (8 years, 1 month ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.1:	+0 -0 lines
State:	*FILE REMOVED*
Log Message:	drop local copies of Map.java and KeyValueHolder.java
#	User	Rev	Content
1	jsr166	1.1	/*
2			* Copyright (c) 2015, 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
23			* questions.
24			*/
25
26			package java.util;
27
28			/**
29			* An immutable container for a key and a value, suitable for use
30			* in creating and populating {@code Map} instances.
31			*
32			* <p>This is a <a href="../lang/doc-files/ValueBased.html">value-based</a>
33			* class; use of identity-sensitive operations (including reference equality
34			* ({@code ==}), identity hash code, or synchronization) on instances of
35			* {@code KeyValueHolder} may have unpredictable results and should be avoided.
36			*
37			* @apiNote
38			* This class is not public. Instances can be created using the
39			* {@link Map#entry Map.entry(k, v)} factory method, which is public.
40			*
41			* <p>This class differs from AbstractMap.SimpleImmutableEntry in the following ways:
42			* it is not serializable, it is final, and its key and value must be non-null.
43			*
44			* @param <K> the key type
45			* @param <V> the value type
46			*
47			* @see Map#ofEntries Map.ofEntries()
48			* @since 9
49			*/
50			final class KeyValueHolder<K,V> implements Map.Entry<K,V> {
51			final K key;
52			final V value;
53
54			KeyValueHolder(K k, V v) {
55			key = Objects.requireNonNull(k);
56			value = Objects.requireNonNull(v);
57			}
58
59			/**
60			* Gets the key from this holder.
61			*
62			* @return the key
63			*/
64			@Override
65			public K getKey() {
66			return key;
67			}
68
69			/**
70			* Gets the value from this holder.
71			*
72			* @return the value
73			*/
74			@Override
75			public V getValue() {
76			return value;
77			}
78
79			/**
80			* Throws {@link UnsupportedOperationException}.
81			*
82			* @param value ignored
83			* @return never returns normally
84			*/
85			@Override
86			public V setValue(V value) {
87			throw new UnsupportedOperationException("not supported");
88			}
89
90			/**
91			* Compares the specified object with this entry for equality.
92			* Returns {@code true} if the given object is also a map entry and
93			* the two entries' keys and values are equal. Note that key and
94			* value are non-null, so equals() can be called safely on them.
95			*/
96			@Override
97			public boolean equals(Object o) {
98			if (!(o instanceof Map.Entry))
99			return false;
100			Map.Entry<?,?> e = (Map.Entry<?,?>)o;
101			return key.equals(e.getKey()) && value.equals(e.getValue());
102			}
103
104			/**
105			* Returns the hash code value for this map entry. The hash code
106			* is {@code key.hashCode() ^ value.hashCode()}. Note that key and
107			* value are non-null, so hashCode() can be called safely on them.
108			*/
109			@Override
110			public int hashCode() {
111			return key.hashCode() ^ value.hashCode();
112			}
113
114			/**
115			* Returns a String representation of this map entry. This
116			* implementation returns the string representation of this
117			* entry's key followed by the equals character ("{@code =}")
118			* followed by the string representation of this entry's value.
119			*
120			* @return a String representation of this map entry
121			*/
122			@Override
123			public String toString() {
124			return key + "=" + value;
125			}
126			}