Moved from superpackage
git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/lang/trunk@137016 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne
parent
a9af49e61d
commit
e4da822d41
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@ -0,0 +1,570 @@
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/* ====================================================================
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* The Apache Software License, Version 1.1
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*
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* Copyright (c) 2002 The Apache Software Foundation. All rights
|
||||
* reserved.
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*
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* Redistribution and use in source and binary forms, with or without
|
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* modification, are permitted provided that the following conditions
|
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* are met:
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*
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||||
* 1. Redistributions of source code must retain the above copyright
|
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* notice, this list of conditions and the following disclaimer.
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*
|
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* 2. Redistributions in binary form must reproduce the above copyright
|
||||
* notice, this list of conditions and the following disclaimer in
|
||||
* the documentation and/or other materials provided with the
|
||||
* distribution.
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*
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* 3. The end-user documentation included with the redistribution, if
|
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* any, must include the following acknowlegement:
|
||||
* "This product includes software developed by the
|
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* Apache Software Foundation (http://www.apache.org/)."
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* Alternately, this acknowlegement may appear in the software itself,
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* if and wherever such third-party acknowlegements normally appear.
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*
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* 4. The names "The Jakarta Project", "Commons", and "Apache Software
|
||||
* Foundation" must not be used to endorse or promote products derived
|
||||
* from this software without prior written permission. For written
|
||||
* permission, please contact apache@apache.org.
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*
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* 5. Products derived from this software may not be called "Apache"
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* nor may "Apache" appear in their names without prior written
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* permission of the Apache Software Foundation.
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*
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
|
||||
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
||||
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
|
||||
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
|
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
||||
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
|
||||
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
|
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
|
||||
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
||||
* SUCH DAMAGE.
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* ====================================================================
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*
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* This software consists of voluntary contributions made by many
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* individuals on behalf of the Apache Software Foundation. For more
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* information on the Apache Software Foundation, please see
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* <http://www.apache.org/>.
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*/
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package org.apache.commons.lang.builder;
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import java.lang.reflect.Field;
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import java.lang.reflect.Modifier;
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/**
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* <code>HashCode</code> generation routines.
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* <p>
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* This class enables a good hashcode to be built for any class. It follows
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* the rules laid out in the book Effective Java, by Joshua Bloch. Writing a
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* good hashCode is actually quite difficult. This class aims to simplify the
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* process.
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* <p>
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* All relevant fields from the object should be included in the hashCode. Derived
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* fields may be excluded. In general, any field used in the equals method must be
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* used in the hashCode method.
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* <p>
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* To use this class write code as follows:
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* <code>
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* public class Person {
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* String name;
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* int age;
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* boolean isSmoker;
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* ...
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*
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* public int hashCode() {
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* // you pick a hard-coded, randomly chosen, non-zero, odd number
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* // ideally different for each class
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* return new HashCodeBuilder(17, 37).
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* append(name).
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* append(age).
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* append(smoker).
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* toHashCode();
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* }
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* }
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* </code>
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* <p>
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* Alternatively, there is a method that uses reflection to determine
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* the fields to test. Because these fields are usually private, the method,
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* <code>reflectionTest</code>, uses <code>Field.setAccessible</code> to change
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* the visibility of the fields. This will fail under a security manager,
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* unless the appropriate permissions are set. It is also slower than testing
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* explicitly.
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* <p>
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* A typical invocation for this method would look like:
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* <code>
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* public boolean hashCode(Object o) {
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* return HashCodeBuilder.reflectionHashCode(this);
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* }
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* </code>
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*
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* @author <a href="mailto:scolebourne@joda.org">Stephen Colebourne</a>
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* @version $Id: HashCodeBuilder.java,v 1.1 2002/09/12 21:59:01 scolebourne Exp $
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*/
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public class HashCodeBuilder {
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/**
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* Constant to use in building the hashCode
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*/
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private final int iConstant;
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/**
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* Running total of the hashCode
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*/
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private int iTotal = 0;
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/**
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* Constructor for HashCodeBuilder.
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* This constructor uses two hard coded choices for the constants needed
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* to build a hashCode.
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*/
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public HashCodeBuilder() {
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super();
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iConstant = 37;
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iTotal = 17;
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}
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/**
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* Constructor for HashCodeBuilder.
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* Two randomly chosen, non-zero, odd numbers must be passed in. Ideally
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* these should be different for each class, however this is not vital.
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* Prime numbers are preferred, especially for the multiplier.
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*
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* @param initialNonZeroOddNumber
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* @param multiplierNonZeroOddNumber
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* @throws IllegalArgumentException if the number is zero or even
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*/
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public HashCodeBuilder(int initialNonZeroOddNumber, int multiplierNonZeroOddNumber) {
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super();
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if (initialNonZeroOddNumber == 0) {
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throw new IllegalArgumentException("HashCodeBuilder requires a non zero initial value");
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}
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if (initialNonZeroOddNumber % 2 == 0) {
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throw new IllegalArgumentException("HashCodeBuilder requires an odd initial value");
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}
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if (multiplierNonZeroOddNumber == 0) {
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throw new IllegalArgumentException("HashCodeBuilder requires a non zero multiplier");
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}
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if (multiplierNonZeroOddNumber % 2 == 0) {
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throw new IllegalArgumentException("HashCodeBuilder requires an odd multiplier");
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}
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iConstant = multiplierNonZeroOddNumber;
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iTotal = initialNonZeroOddNumber;
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}
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//-------------------------------------------------------------------------
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/**
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* This method uses reflection to build a valid hash code.
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* <p>
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* It uses Field.setAccessible to gain access to private fields. This means
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* that it will throw a security exception if run under a security manger, if
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* the permissions are not set up.
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* It is also not as efficient as testing explicitly.
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* Transient members will be not be used, as they are likely derived
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* fields, and not part of the value of the object.
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* This constructor uses two hard coded choices for the constants needed
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* to build a hash code.
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*
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* @param object the object to create a hash code for
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* @return int hash code
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* @throws IllegalArgumentException if the object is null
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*/
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public static int reflectionHashCode(Object object) {
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return reflectionHashCode(object, false);
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}
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/**
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* This method uses reflection to build a valid hash code.
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* <p>
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* It uses Field.setAccessible to gain access to private fields. This means
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* that it will throw a security exception if run under a security manger, if
|
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* the permissions are not set up.
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* It is also not as efficient as testing explicitly.
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* Transient members will be not be used, as they are likely derived
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* fields, and not part of the value of the object.
|
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* <p>
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* Two randomly chosen, non-zero, odd numbers must be passed in. Ideally
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* these should be different for each class, however this is not vital.
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* Prime numbers are preferred, especially for the multiplier.
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*
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* @param initialNonZeroOddNumber
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* @param multiplierNonZeroOddNumber
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* @param object the object to create a hash code for
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* @return int hash code
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* @throws IllegalArgumentException if the object is null
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* @throws IllegalArgumentException if the number is zero or even
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*/
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public static int reflectionHashCode(
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int initialNonZeroOddNumber, int multiplierNonZeroOddNumber,
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Object object) {
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return reflectionHashCode(initialNonZeroOddNumber, multiplierNonZeroOddNumber, object);
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}
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/**
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* This method uses reflection to build a valid hash code.
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* <p>
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* It uses Field.setAccessible to gain access to private fields. This means
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* that it will throw a security exception if run under a security manger, if
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* the permissions are not set up.
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* It is also not as efficient as testing explicitly.
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* If the TestTransients parameter is set to true, transient members will be
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* tested, otherwise they are ignored, as they are likely derived fields, and
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* not part of the value of the object.
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* This constructor uses two hard coded choices for the constants needed
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* to build a hash code.
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*
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* @param object the object to create a hash code for
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* @param testTransients whether to include transient fields
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* @return int hash code
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* @throws IllegalArgumentException if the object is null
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*/
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public static int reflectionHashCode(Object object, boolean testTransients) {
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return reflectionHashCode(17, 37, object, testTransients);
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}
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/**
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* This method uses reflection to build a valid hash code.
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* <p>
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* It uses Field.setAccessible to gain access to private fields. This means
|
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* that it will throw a security exception if run under a security manger, if
|
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* the permissions are not set up.
|
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* It is also not as efficient as testing explicitly.
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* If the TestTransients parameter is set to true, transient members will be
|
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* tested, otherwise they are ignored, as they are likely derived fields, and
|
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* not part of the value of the object.
|
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* <p>
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* Two randomly chosen, non-zero, odd numbers must be passed in. Ideally
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* these should be different for each class, however this is not vital.
|
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* Prime numbers are preferred, especially for the multiplier.
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*
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* @param initialNonZeroOddNumber
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* @param multiplierNonZeroOddNumber
|
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* @param object the object to create a hash code for
|
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* @param testTransients whether to include transient fields
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* @return int hash code
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* @throws IllegalArgumentException if the object is null
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* @throws IllegalArgumentException if the number is zero or even
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*/
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public static int reflectionHashCode(
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int initialNonZeroOddNumber, int multiplierNonZeroOddNumber,
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Object object, boolean testTransients) {
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if (object == null) {
|
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throw new IllegalArgumentException("The object to build a hash code for must not be null");
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}
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HashCodeBuilder hashCodeBuilder = new HashCodeBuilder(initialNonZeroOddNumber, multiplierNonZeroOddNumber);
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Field[] fields = object.getClass().getDeclaredFields();
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Field.setAccessible(fields, true);
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for (int i = 0; i < fields.length; ++i) {
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Field f = fields[i];
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if (testTransients || !Modifier.isTransient(f.getModifiers())) {
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try {
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hashCodeBuilder.append(f.get(object));
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} catch (IllegalAccessException e) {
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//this can't happen. Would get a Security exception instead
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//throw a runtime exception in case the impossible happens.
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throw new InternalError("Unexpected IllegalAccessException");
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}
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}
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}
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return hashCodeBuilder.toHashCode();
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}
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//-------------------------------------------------------------------------
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/**
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* Append a hashCode for an Object.
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*
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* @param object the object to add to the hashCode
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* @return this
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*/
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public HashCodeBuilder append(Object object) {
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if (object == null) {
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iTotal = iTotal * iConstant;
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} else {
|
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if (object.getClass().isArray() == false) {
|
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//the simple case, not an array, just the element
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iTotal = iTotal * iConstant + object.hashCode();
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|
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} else {
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//'Switch' on type of array, to dispatch to the correct handler
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// This handles multi dimensional arrays
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if (object instanceof long[]) {
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append((long[]) object);
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} else if (object instanceof int[]) {
|
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append((int[]) object);
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} else if (object instanceof short[]) {
|
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append((short[]) object);
|
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} else if (object instanceof char[]) {
|
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append((char[]) object);
|
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} else if (object instanceof byte[]) {
|
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append((byte[]) object);
|
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} else if (object instanceof double[]) {
|
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append((double[]) object);
|
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} else if (object instanceof float[]) {
|
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append((float[]) object);
|
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} else if (object instanceof boolean[]) {
|
||||
append((boolean[]) object);
|
||||
} else {
|
||||
// Not an array of primitives
|
||||
append((Object[]) object);
|
||||
}
|
||||
}
|
||||
}
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a long.
|
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*
|
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* @param value the long to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(long value) {
|
||||
iTotal = iTotal * iConstant + ((int) (value ^ (value >> 32)));
|
||||
return this;
|
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}
|
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|
||||
/**
|
||||
* Append a hashCode for an int.
|
||||
*
|
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* @param value the int to add to the hashCode
|
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* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(int value) {
|
||||
iTotal = iTotal * iConstant + value;
|
||||
return this;
|
||||
}
|
||||
|
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/**
|
||||
* Append a hashCode for a short.
|
||||
*
|
||||
* @param value the short to add to the hashCode
|
||||
* @return this
|
||||
*/
|
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public HashCodeBuilder append(short value) {
|
||||
iTotal = iTotal * iConstant + (int) value;
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a char.
|
||||
*
|
||||
* @param value the char to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(char value) {
|
||||
iTotal = iTotal * iConstant + (int) value;
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a byte.
|
||||
*
|
||||
* @param value the byte to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(byte value) {
|
||||
iTotal = iTotal * iConstant + (int) value;
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a double.
|
||||
*
|
||||
* @param value the double to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(double value) {
|
||||
return append(Double.doubleToLongBits(value));
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a float.
|
||||
*
|
||||
* @param value the float to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(float value) {
|
||||
iTotal = iTotal * iConstant + Float.floatToIntBits(value);
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a long.
|
||||
*
|
||||
* @param value the long to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(boolean value) {
|
||||
iTotal = iTotal * iConstant + (value ? 0 : 1);
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for an Object array.
|
||||
*
|
||||
* @param array the array to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(Object[] array) {
|
||||
if (array == null) {
|
||||
iTotal = iTotal * iConstant;
|
||||
} else {
|
||||
for (int i = 0; i < array.length; i++) {
|
||||
append(array[i]);
|
||||
}
|
||||
}
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a long array.
|
||||
*
|
||||
* @param array the array to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(long[] array) {
|
||||
if (array == null) {
|
||||
iTotal = iTotal * iConstant;
|
||||
} else {
|
||||
for (int i = 0; i < array.length; i++) {
|
||||
append(array[i]);
|
||||
}
|
||||
}
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for an int array.
|
||||
*
|
||||
* @param array the array to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(int[] array) {
|
||||
if (array == null) {
|
||||
iTotal = iTotal * iConstant;
|
||||
} else {
|
||||
for (int i = 0; i < array.length; i++) {
|
||||
append(array[i]);
|
||||
}
|
||||
}
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a short array.
|
||||
*
|
||||
* @param array the array to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(short[] array) {
|
||||
if (array == null) {
|
||||
iTotal = iTotal * iConstant;
|
||||
} else {
|
||||
for (int i = 0; i < array.length; i++) {
|
||||
append(array[i]);
|
||||
}
|
||||
}
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a char array.
|
||||
*
|
||||
* @param array the array to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(char[] array) {
|
||||
if (array == null) {
|
||||
iTotal = iTotal * iConstant;
|
||||
} else {
|
||||
for (int i = 0; i < array.length; i++) {
|
||||
append(array[i]);
|
||||
}
|
||||
}
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a byte array.
|
||||
*
|
||||
* @param array the array to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(byte[] array) {
|
||||
if (array == null) {
|
||||
iTotal = iTotal * iConstant;
|
||||
} else {
|
||||
for (int i = 0; i < array.length; i++) {
|
||||
append(array[i]);
|
||||
}
|
||||
}
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a double array.
|
||||
*
|
||||
* @param array the array to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(double[] array) {
|
||||
if (array == null) {
|
||||
iTotal = iTotal * iConstant;
|
||||
} else {
|
||||
for (int i = 0; i < array.length; i++) {
|
||||
append(array[i]);
|
||||
}
|
||||
}
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a float array.
|
||||
*
|
||||
* @param array the array to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(float[] array) {
|
||||
if (array == null) {
|
||||
iTotal = iTotal * iConstant;
|
||||
} else {
|
||||
for (int i = 0; i < array.length; i++) {
|
||||
append(array[i]);
|
||||
}
|
||||
}
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Append a hashCode for a boolean array.
|
||||
*
|
||||
* @param array the array to add to the hashCode
|
||||
* @return this
|
||||
*/
|
||||
public HashCodeBuilder append(boolean[] array) {
|
||||
if (array == null) {
|
||||
iTotal = iTotal * iConstant;
|
||||
} else {
|
||||
for (int i = 0; i < array.length; i++) {
|
||||
append(array[i]);
|
||||
}
|
||||
}
|
||||
return this;
|
||||
}
|
||||
|
||||
/**
|
||||
* Return the computed hashCode
|
||||
*
|
||||
* @return int hashCode based on the fields appended
|
||||
*/
|
||||
public int toHashCode() {
|
||||
return iTotal;
|
||||
}
|
||||
|
||||
}
|
||||
Loading…
Reference in New Issue