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Groovy example source code file (HashCodeHelper.java)

This example Groovy source code file (HashCodeHelper.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

hashcodehelper, hashcodehelper, mult, mult, object, object, seed, seed, util

The Groovy HashCodeHelper.java source code

/*
 * Copyright 2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.codehaus.groovy.util;

import java.util.Arrays;

/**
 * A utility class to help calculate hashcode values
 * using an algorithm similar to that outlined in
 * "Effective Java, Joshua Bloch, 2nd Edition".
 */
public class HashCodeHelper {
    private static final int SEED = 127;
    private static final int MULT = 31;

    public static int initHash() {
        return SEED;
    }

    public static int updateHash(int current, boolean var) {
        return shift(current) + (var ? 1 : 0);
    }

    public static int updateHash(int current, char var) {
        return shift(current) + (int) var;
    }

    public static int updateHash(int current, int var) {
        return shift(current) + var;
    }

    public static int updateHash(int current, long var) {
        return shift(current) + (int) (var ^ (var >>> 32));
    }

    public static int updateHash(int current, float var) {
        return updateHash(current, Float.floatToIntBits(var));
    }

    public static int updateHash(int current, double var) {
        return updateHash(current, Double.doubleToLongBits(var));
    }

    public static int updateHash(int current, Object var) {
        if (var == null) return updateHash(current, 0);
        if (var.getClass().isArray())
            return shift(current) + Arrays.hashCode((Object[]) var);
        return updateHash(current, var.hashCode());
    }

    public static int updateHash(int current, boolean[] var) {
        if (var == null) return updateHash(current, 0);
        return shift(current) + Arrays.hashCode(var);
    }

    public static int updateHash(int current, char[] var) {
        if (var == null) return updateHash(current, 0);
        return shift(current) + Arrays.hashCode(var);
    }

    public static int updateHash(int current, byte[] var) {
        if (var == null) return updateHash(current, 0);
        return shift(current) + Arrays.hashCode(var);
    }

    public static int updateHash(int current, short[] var) {
        if (var == null) return updateHash(current, 0);
        return shift(current) + Arrays.hashCode(var);
    }

    public static int updateHash(int current, int[] var) {
        if (var == null) return updateHash(current, 0);
        return shift(current) + Arrays.hashCode(var);
    }

    public static int updateHash(int current, long[] var) {
        if (var == null) return updateHash(current, 0);
        return shift(current) + Arrays.hashCode(var);
    }

    public static int updateHash(int current, float[] var) {
        if (var == null) return updateHash(current, 0);
        return shift(current) + Arrays.hashCode(var);
    }

    public static int updateHash(int current, double[] var) {
        if (var == null) return updateHash(current, 0);
        return shift(current) + Arrays.hashCode(var);
    }

    private static int shift(int current) {
        return MULT * current;
    }

}

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