All Downloads are FREE. Search and download functionalities are using the official Maven repository.

com.itextpdf.awt.geom.misc.HashCode Maven / Gradle / Ivy

/*
 *  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.
 *
 *  This code was originally part of the Apache Harmony project.
 *  The Apache Harmony project has been discontinued.
 *  That's why we imported the code into iText.
 */

package com.itextpdf.awt.geom.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
 * java.util.List.hashCode.
 * 
 * If you need order independent hash code just summate, multiply or XOR all
 * elements.
 * 
 * 

* Suppose we have class: * *


 * class Thing {
 *     long id;
 *     String name;
 *     float weight;
 * }
 * 
* * The hash code calculation can be expressed in 2 forms. * *

* For maximum performance: * *


 * 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;
 * }
 * 
* *

* For convenience:

 * public int hashCode() {
 *     return new HashCode().append(id).append(name).append(weight).hashCode();
 * }
 * 
* * @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; } }




© 2015 - 2024 Weber Informatics LLC | Privacy Policy