Java Hash Calculate hash(Object object)

Description

Returns a hash code for non-null Object x.

License

Apache License

Parameter

Parameter	Description
object	the object serving as a key

Return

the hash code

Declaration

public static int hash(Object object) 

Method Source Code

//package com.java2s;
/*/*from   w  w w  .  j  av a 2 s . c om*/
 * Copyright 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);
    }
}

Related

1. hash(Object key, int limit)
2. hash(Object o)
3. hash(Object obj)
4. hash(Object obj)
5. hash(Object obj)
6. hash(Object v)
7. hash(Object value)
8. hash(Object value, int seed)
9. hash(Object... as)