| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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.apache.harmony.misc; |
| |
| /** |
| * This class is a convenience method to sequentially calculate hash code of the |
| * object based on the field values. The result depends on the order of elements |
| * appended. The exact formula is the same as for |
| * <code>java.util.List.hashCode</code>. |
| * |
| * If you need order independent hash code just summate, multiply or XOR all |
| * elements. |
| * |
| * <p> |
| * Suppose we have class: |
| * |
| * <pre><code> |
| * class Thing { |
| * long id; |
| * String name; |
| * float weight; |
| * } |
| * </code></pre> |
| * |
| * The hash code calculation can be expressed in 2 forms. |
| * |
| * <p> |
| * For maximum performance: |
| * |
| * <pre><code> |
| * public int hashCode() { |
| * int hashCode = HashCode.EMPTY_HASH_CODE; |
| * hashCode = HashCode.combine(hashCode, id); |
| * hashCode = HashCode.combine(hashCode, name); |
| * hashCode = HashCode.combine(hashCode, weight); |
| * return hashCode; |
| * } |
| * </code></pre> |
| * |
| * <p> |
| * For convenience: <code><pre> |
| * public int hashCode() { |
| * return new HashCode().append(id).append(name).append(weight).hashCode(); |
| * } |
| * </code></pre> |
| * |
| * @see java.util.List#hashCode() |
| */ |
| public final class HashCode { |
| /** |
| * The hashCode value before any data is appended, equals to 1. |
| * @see java.util.List#hashCode() |
| */ |
| public static final int EMPTY_HASH_CODE = 1; |
| |
| private int hashCode = EMPTY_HASH_CODE; |
| |
| /** |
| * Returns accumulated hashCode |
| */ |
| public final int hashCode() { |
| return hashCode; |
| } |
| |
| /** |
| * Combines hashCode of previous elements sequence and value's hashCode. |
| * @param hashCode previous hashCode value |
| * @param value new element |
| * @return combined hashCode |
| */ |
| public static int combine(int hashCode, boolean value) { |
| int v = value ? 1231 : 1237; |
| return combine(hashCode, v); |
| } |
| |
| /** |
| * Combines hashCode of previous elements sequence and value's hashCode. |
| * @param hashCode previous hashCode value |
| * @param value new element |
| * @return combined hashCode |
| */ |
| public static int combine(int hashCode, long value) { |
| int v = (int) (value ^ (value >>> 32)); |
| return combine(hashCode, v); |
| } |
| |
| /** |
| * Combines hashCode of previous elements sequence and value's hashCode. |
| * @param hashCode previous hashCode value |
| * @param value new element |
| * @return combined hashCode |
| */ |
| public static int combine(int hashCode, float value) { |
| int v = Float.floatToIntBits(value); |
| return combine(hashCode, v); |
| } |
| |
| /** |
| * Combines hashCode of previous elements sequence and value's hashCode. |
| * @param hashCode previous hashCode value |
| * @param value new element |
| * @return combined hashCode |
| */ |
| public static int combine(int hashCode, double value) { |
| long v = Double.doubleToLongBits(value); |
| return combine(hashCode, v); |
| } |
| |
| /** |
| * Combines hashCode of previous elements sequence and value's hashCode. |
| * @param hashCode previous hashCode value |
| * @param value new element |
| * @return combined hashCode |
| */ |
| public static int combine(int hashCode, Object value) { |
| return combine(hashCode, value.hashCode()); |
| } |
| |
| /** |
| * Combines hashCode of previous elements sequence and value's hashCode. |
| * @param hashCode previous hashCode value |
| * @param value new element |
| * @return combined hashCode |
| */ |
| public static int combine(int hashCode, int value) { |
| return 31 * hashCode + value; |
| } |
| |
| /** |
| * Appends value's hashCode to the current hashCode. |
| * @param value new element |
| * @return this |
| */ |
| public final HashCode append(int value) { |
| hashCode = combine(hashCode, value); |
| return this; |
| } |
| |
| /** |
| * Appends value's hashCode to the current hashCode. |
| * @param value new element |
| * @return this |
| */ |
| public final HashCode append(long value) { |
| hashCode = combine(hashCode, value); |
| return this; |
| } |
| |
| /** |
| * Appends value's hashCode to the current hashCode. |
| * @param value new element |
| * @return this |
| */ |
| public final HashCode append(float value) { |
| hashCode = combine(hashCode, value); |
| return this; |
| } |
| |
| /** |
| * Appends value's hashCode to the current hashCode. |
| * @param value new element |
| * @return this |
| */ |
| public final HashCode append(double value) { |
| hashCode = combine(hashCode, value); |
| return this; |
| } |
| |
| /** |
| * Appends value's hashCode to the current hashCode. |
| * @param value new element |
| * @return this |
| */ |
| public final HashCode append(boolean value) { |
| hashCode = combine(hashCode, value); |
| return this; |
| } |
| |
| /** |
| * Appends value's hashCode to the current hashCode. |
| * @param value new element |
| * @return this |
| */ |
| public final HashCode append(Object value) { |
| hashCode = combine(hashCode, value); |
| return this; |
| } |
| } |