Java tutorial
//package com.java2s; /** * Copyright 2003-2010 Terracotta, Inc. * * 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. */ public class Main { private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_1 = 20; private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_2 = 12; private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_3 = 7; private static final int DOUG_LEA_BLACK_MAGIC_OPERAND_4 = 4; /** * Returns a hash code for non-null Object x. * <p/> * This function ensures that hashCodes that differ only by * constant multiples at each bit position have a bounded * number of collisions. (Doug Lea) * * @param object the object serving as a key * @return the hash code */ public static int hash(Object object) { int h = object.hashCode(); h ^= (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_1) ^ (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_2); return h ^ (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_3) ^ (h >>> DOUG_LEA_BLACK_MAGIC_OPERAND_4); } }