From e4da822d419cac03359d25404e81c4130dbcb3a1 Mon Sep 17 00:00:00 2001 From: Stephen Colebourne Date: Thu, 12 Sep 2002 21:59:01 +0000 Subject: [PATCH] Moved from superpackage git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/lang/trunk@137016 13f79535-47bb-0310-9956-ffa450edef68 --- .../commons/lang/builder/HashCodeBuilder.java | 570 ++++++++++++++++++ 1 file changed, 570 insertions(+) create mode 100644 src/java/org/apache/commons/lang/builder/HashCodeBuilder.java diff --git a/src/java/org/apache/commons/lang/builder/HashCodeBuilder.java b/src/java/org/apache/commons/lang/builder/HashCodeBuilder.java new file mode 100644 index 000000000..ee5b4003c --- /dev/null +++ b/src/java/org/apache/commons/lang/builder/HashCodeBuilder.java @@ -0,0 +1,570 @@ +/* ==================================================================== + * The Apache Software License, Version 1.1 + * + * Copyright (c) 2002 The Apache Software Foundation. All rights + * reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * 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. + * + * 3. The end-user documentation included with the redistribution, if + * any, must include the following acknowlegement: + * "This product includes software developed by the + * Apache Software Foundation (http://www.apache.org/)." + * Alternately, this acknowlegement may appear in the software itself, + * if and wherever such third-party acknowlegements normally appear. + * + * 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. + * + * 5. Products derived from this software may not be called "Apache" + * nor may "Apache" appear in their names without prior written + * permission of the Apache Software Foundation. + * + * 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 + * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * 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 + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * ==================================================================== + * + * This software consists of voluntary contributions made by many + * individuals on behalf of the Apache Software Foundation. For more + * information on the Apache Software Foundation, please see + * . + */ +package org.apache.commons.lang.builder; + +import java.lang.reflect.Field; +import java.lang.reflect.Modifier; +/** + * HashCode generation routines. + *

+ * This class enables a good hashcode to be built for any class. It follows + * the rules laid out in the book Effective Java, by Joshua Bloch. Writing a + * good hashCode is actually quite difficult. This class aims to simplify the + * process. + *

+ * All relevant fields from the object should be included in the hashCode. Derived + * fields may be excluded. In general, any field used in the equals method must be + * used in the hashCode method. + *

+ * To use this class write code as follows: + * + * public class Person { + * String name; + * int age; + * boolean isSmoker; + * ... + * + * public int hashCode() { + * // you pick a hard-coded, randomly chosen, non-zero, odd number + * // ideally different for each class + * return new HashCodeBuilder(17, 37). + * append(name). + * append(age). + * append(smoker). + * toHashCode(); + * } + * } + * + *

+ * Alternatively, there is a method that uses reflection to determine + * the fields to test. Because these fields are usually private, the method, + * reflectionTest, uses Field.setAccessible to change + * the visibility of the fields. This will fail under a security manager, + * unless the appropriate permissions are set. It is also slower than testing + * explicitly. + *

+ * A typical invocation for this method would look like: + * + * public boolean hashCode(Object o) { + * return HashCodeBuilder.reflectionHashCode(this); + * } + * + * + * @author Stephen Colebourne + * @version $Id: HashCodeBuilder.java,v 1.1 2002/09/12 21:59:01 scolebourne Exp $ + */ +public class HashCodeBuilder { + + /** + * Constant to use in building the hashCode + */ + private final int iConstant; + /** + * Running total of the hashCode + */ + private int iTotal = 0; + + /** + * Constructor for HashCodeBuilder. + * This constructor uses two hard coded choices for the constants needed + * to build a hashCode. + */ + public HashCodeBuilder() { + super(); + iConstant = 37; + iTotal = 17; + } + + /** + * Constructor for HashCodeBuilder. + * Two randomly chosen, non-zero, odd numbers must be passed in. Ideally + * these should be different for each class, however this is not vital. + * Prime numbers are preferred, especially for the multiplier. + * + * @param initialNonZeroOddNumber + * @param multiplierNonZeroOddNumber + * @throws IllegalArgumentException if the number is zero or even + */ + public HashCodeBuilder(int initialNonZeroOddNumber, int multiplierNonZeroOddNumber) { + super(); + if (initialNonZeroOddNumber == 0) { + throw new IllegalArgumentException("HashCodeBuilder requires a non zero initial value"); + } + if (initialNonZeroOddNumber % 2 == 0) { + throw new IllegalArgumentException("HashCodeBuilder requires an odd initial value"); + } + if (multiplierNonZeroOddNumber == 0) { + throw new IllegalArgumentException("HashCodeBuilder requires a non zero multiplier"); + } + if (multiplierNonZeroOddNumber % 2 == 0) { + throw new IllegalArgumentException("HashCodeBuilder requires an odd multiplier"); + } + iConstant = multiplierNonZeroOddNumber; + iTotal = initialNonZeroOddNumber; + } + + //------------------------------------------------------------------------- + + /** + * This method uses reflection to build a valid hash code. + *

+ * It uses Field.setAccessible to gain access to private fields. This means + * that it will throw a security exception if run under a security manger, if + * the permissions are not set up. + * It is also not as efficient as testing explicitly. + * Transient members will be not be used, as they are likely derived + * fields, and not part of the value of the object. + * This constructor uses two hard coded choices for the constants needed + * to build a hash code. + * + * @param object the object to create a hash code for + * @return int hash code + * @throws IllegalArgumentException if the object is null + */ + public static int reflectionHashCode(Object object) { + return reflectionHashCode(object, false); + } + + /** + * This method uses reflection to build a valid hash code. + *

+ * It uses Field.setAccessible to gain access to private fields. This means + * that it will throw a security exception if run under a security manger, if + * the permissions are not set up. + * It is also not as efficient as testing explicitly. + * Transient members will be not be used, as they are likely derived + * fields, and not part of the value of the object. + *

+ * Two randomly chosen, non-zero, odd numbers must be passed in. Ideally + * these should be different for each class, however this is not vital. + * Prime numbers are preferred, especially for the multiplier. + * + * @param initialNonZeroOddNumber + * @param multiplierNonZeroOddNumber + * @param object the object to create a hash code for + * @return int hash code + * @throws IllegalArgumentException if the object is null + * @throws IllegalArgumentException if the number is zero or even + */ + public static int reflectionHashCode( + int initialNonZeroOddNumber, int multiplierNonZeroOddNumber, + Object object) { + return reflectionHashCode(initialNonZeroOddNumber, multiplierNonZeroOddNumber, object); + } + + /** + * This method uses reflection to build a valid hash code. + *

+ * It uses Field.setAccessible to gain access to private fields. This means + * that it will throw a security exception if run under a security manger, if + * the permissions are not set up. + * It is also not as efficient as testing explicitly. + * If the TestTransients parameter is set to true, transient members will be + * tested, otherwise they are ignored, as they are likely derived fields, and + * not part of the value of the object. + * This constructor uses two hard coded choices for the constants needed + * to build a hash code. + * + * @param object the object to create a hash code for + * @param testTransients whether to include transient fields + * @return int hash code + * @throws IllegalArgumentException if the object is null + */ + public static int reflectionHashCode(Object object, boolean testTransients) { + return reflectionHashCode(17, 37, object, testTransients); + } + + /** + * This method uses reflection to build a valid hash code. + *

+ * It uses Field.setAccessible to gain access to private fields. This means + * that it will throw a security exception if run under a security manger, if + * the permissions are not set up. + * It is also not as efficient as testing explicitly. + * If the TestTransients parameter is set to true, transient members will be + * tested, otherwise they are ignored, as they are likely derived fields, and + * not part of the value of the object. + *

+ * Two randomly chosen, non-zero, odd numbers must be passed in. Ideally + * these should be different for each class, however this is not vital. + * Prime numbers are preferred, especially for the multiplier. + * + * @param initialNonZeroOddNumber + * @param multiplierNonZeroOddNumber + * @param object the object to create a hash code for + * @param testTransients whether to include transient fields + * @return int hash code + * @throws IllegalArgumentException if the object is null + * @throws IllegalArgumentException if the number is zero or even + */ + public static int reflectionHashCode( + int initialNonZeroOddNumber, int multiplierNonZeroOddNumber, + Object object, boolean testTransients) { + + if (object == null) { + throw new IllegalArgumentException("The object to build a hash code for must not be null"); + } + HashCodeBuilder hashCodeBuilder = new HashCodeBuilder(initialNonZeroOddNumber, multiplierNonZeroOddNumber); + Field[] fields = object.getClass().getDeclaredFields(); + Field.setAccessible(fields, true); + for (int i = 0; i < fields.length; ++i) { + Field f = fields[i]; + if (testTransients || !Modifier.isTransient(f.getModifiers())) { + try { + hashCodeBuilder.append(f.get(object)); + } catch (IllegalAccessException e) { + //this can't happen. Would get a Security exception instead + //throw a runtime exception in case the impossible happens. + throw new InternalError("Unexpected IllegalAccessException"); + } + } + } + return hashCodeBuilder.toHashCode(); + } + + //------------------------------------------------------------------------- + + /** + * Append a hashCode for an Object. + * + * @param object the object to add to the hashCode + * @return this + */ + public HashCodeBuilder append(Object object) { + if (object == null) { + iTotal = iTotal * iConstant; + + } else { + if (object.getClass().isArray() == false) { + //the simple case, not an array, just the element + iTotal = iTotal * iConstant + object.hashCode(); + + } else { + //'Switch' on type of array, to dispatch to the correct handler + // This handles multi dimensional arrays + if (object instanceof long[]) { + append((long[]) object); + } else if (object instanceof int[]) { + append((int[]) object); + } else if (object instanceof short[]) { + append((short[]) object); + } else if (object instanceof char[]) { + append((char[]) object); + } else if (object instanceof byte[]) { + append((byte[]) object); + } else if (object instanceof double[]) { + append((double[]) object); + } else if (object instanceof float[]) { + append((float[]) object); + } 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. + * + * @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; + } + + /** + * Append a hashCode for an int. + * + * @param value the int to add to the hashCode + * @return this + */ + public HashCodeBuilder append(int value) { + iTotal = iTotal * iConstant + value; + return this; + } + + /** + * Append a hashCode for a short. + * + * @param value the short to add to the hashCode + * @return this + */ + 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; + } + +}