com.sleepycat.collections.MapEntryParameter Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of je Show documentation

Berkeley DB Java Edition is a open source, transactional storage solution for Java applications. The Direct Persistence Layer (DPL) API is faster and easier to develop, deploy, and manage than serialized object files or ORM-based Java persistence solutions. The Collections API enhances the standard java.util.collections classes allowing them to be persisted to a local file system and accessed concurrently while protected by ACID transactions. Data is stored by serializing objects and managing class and instance data separately so as not to waste space. Berkeley DB Java Edition is the reliable drop-in solution for complex, fast, and scalable storage. Source for this release is in 'je-4.0.92-sources.jar', the Javadoc is located at 'http://download.oracle.com/berkeley-db/docs/je/4.0.92/'.

There is a newer version: 5.0.73

Show newest version

/*-
 * Copyright (C) 2002, 2018, Oracle and/or its affiliates. All rights reserved.
 *
 * This file was distributed by Oracle as part of a version of Oracle Berkeley
 * DB Java Edition made available at:
 *
 * http://www.oracle.com/technetwork/database/database-technologies/berkeleydb/downloads/index.html
 *
 * Please see the LICENSE file included in the top-level directory of the
 * appropriate version of Oracle Berkeley DB Java Edition for a copy of the
 * license and additional information.
 */

package com.sleepycat.collections;

import java.util.Map;

/**
 * A simple Map.Entry implementation that can be used as in
 * input parameter.  Since a MapEntryParameter is not obtained
 * from a map, it is not attached to any map in particular.  To emphasize that
 * changing this object does not change the map, the {@link #setValue} method
 * always throws UnsupportedOperationException.
 *
 * Warning: Use of this interface violates the Java Collections
 * interface contract since these state that Map.Entry objects
 * should only be obtained from Map.entrySet() sets, while this
 * class allows constructing them directly.  However, it is useful for
 * performing operations on an entry set such as add(), contains(), etc.  For
 * restrictions see {@link #getValue} and {@link #setValue}.
 *
 * @author Mark Hayes
 */
public class MapEntryParameter implements Map.Entry {

    private K key;
    private V value;

    /**
     * Creates a map entry with a given key and value.
     *
     * @param key is the key to use.
     *
     * @param value is the value to use.
     */
    public MapEntryParameter(K key, V value) {

        this.key = key;
        this.value = value;
    }

    /**
     * Computes a hash code as specified by {@link
     * java.util.Map.Entry#hashCode}.
     *
     * @return the computed hash code.
     */
    public int hashCode() {

        return ((key == null)    ? 0 : key.hashCode()) ^
               ((value == null)  ? 0 : value.hashCode());
    }

    /**
     * Compares this entry to a given entry as specified by {@link
     * java.util.Map.Entry#equals}.
     *
     * @return the computed hash code.
     */
    public boolean equals(Object other) {

        if (!(other instanceof Map.Entry)) {
            return false;
        }

        Map.Entry e = (Map.Entry) other;

        return ((key == null) ? (e.getKey() == null)
                              : key.equals(e.getKey())) &&
               ((value == null) ? (e.getValue() == null)
                                : value.equals(e.getValue()));
    }

    /**
     * Returns the key of this entry.
     *
     * @return the key of this entry.
     */
    public final K getKey() {

        return key;
    }

    /**
     * Returns the value of this entry.  Note that this will be the value
     * passed to the constructor or the last value passed to {@link #setValue}.
     * It will not reflect changes made to a Map.
     *
     * @return the value of this entry.
     */
    public final V getValue() {

        return value;
    }

    /**
     * Always throws UnsupportedOperationException since this
     * object is not attached to a map.
     */
    public V setValue(V newValue) {

        throw new UnsupportedOperationException();
    }

    final void setValueInternal(V newValue) {

        this.value = newValue;
    }

    /**
     * Converts the entry to a string representation for debugging.
     *
     * @return the string representation.
     */
    public String toString() {

        return "[key [" + key + "] value [" + value + ']';
    }
}