com.espertech.esper.collection.MultiKey Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of esper Show documentation
Complex event processing and event series analysis component
The newest version!
/*
 ***************************************************************************************
 *  Copyright (C) 2006 EsperTech, Inc. All rights reserved.                            *
 *  http://www.espertech.com/esper                                                     *
 *  http://www.espertech.com                                                           *
 *  ---------------------------------------------------------------------------------- *
 *  The software in this package is published under the terms of the GPL license       *
 *  a copy of which has been included with this distribution in the license.txt file.  *
 ***************************************************************************************
 */
package com.espertech.esper.collection;

import java.util.Arrays;

/**
 * Functions as a key value for Maps where keys need to be composite values.
 * The class allows a Map that uses MultiKeyUntyped entries for key values to use multiple objects as keys.
 * It calculates the hashCode from the key objects on construction and caches the hashCode.
 */
public final class MultiKey {
    private final T[] keys;
    private final int hashCode;

    /**
     * Constructor for multiple keys supplied in an object array.
     *
     * @param keys is an array of key objects
     */
    public MultiKey(T[] keys) {
        if (keys == null) {
            throw new IllegalArgumentException("The array of keys must not be null");
        }

        int total = 0;
        for (int i = 0; i < keys.length; i++) {
            if (keys[i] != null) {
                total *= 31;
                total ^= keys[i].hashCode();
            }
        }

        this.hashCode = total;
        this.keys = keys;
    }

    /**
     * Returns the number of key objects.
     *
     * @return size of key object array
     */
    public final int size() {
        return keys.length;
    }

    /**
     * Returns the key object at the specified position.
     *
     * @param index is the array position
     * @return key object at position
     */
    public final T get(int index) {
        return keys[index];
    }

    public final boolean equals(Object other) {
        if (other == this) {
            return true;
        }
        if (other instanceof MultiKey) {
            MultiKey otherKeys = (MultiKey) other;
            return Arrays.equals(keys, otherKeys.keys);
        }
        return false;
    }

    public final int hashCode() {
        return hashCode;
    }

    public final String toString() {
        return "MultiKey" + Arrays.asList(keys).toString();
    }

    /**
     * Returns the key value array.
     *
     * @return key value array
     */
    public final T[] getArray() {
        return keys;
    }
}