commons-lang-1.0.1.jar - Apache Commons Lang
commons-lang-1.0.1.jar is the JAR file for Apache Commons Lang 1.0.1, which
provides a host of helper utilities for the java.lang API.
JAR File Size and Download Location:
File name: commons-lang-1.0.1.jar File size: 63980 bytes Date modified: 11/22/2002 Download: Apache Commons Lang Website
✍: FYIcenter.com
⏎ org/apache/commons/lang/builder/HashCodeBuilder.java
/* ====================================================================
* 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
* <http://www.apache.org/>.
*/
package org.apache.commons.lang.builder;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
/**
* <code>HashCode</code> generation routines.
* <p>
* 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.
* <p>
* 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.
* <p>
* To use this class write code as follows:
* <pre>
* 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();
* }
* }
* </pre>
* <p>
* Alternatively, there is a method that uses reflection to determine
* the fields to test. Because these fields are usually private, the method,
* <code>reflectionHashCode</code>, uses <code>Field.setAccessible</code> 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.
* <p>
* A typical invocation for this method would look like:
* <pre>
* public boolean hashCode(Object o) {
* return HashCodeBuilder.reflectionHashCode(this);
* }
* </pre>
*
* @author <a href="mailto:scolebourne@joda.org">Stephen Colebourne</a>
* @version $Id: HashCodeBuilder.java,v 1.4 2002/10/01 20:02:08 stevencaswell 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 a non-zero, odd number used as the initial value
* @param multiplierNonZeroOddNumber a non-zero, odd number used as the multiplier
* @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.
* <p>
* 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.
* Static fields will not be tested.
* 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.
* <p>
* 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.
* Static fields will not be tested.
* 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.
* <p>
* 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.
* Static fields will not be tested.
* <p>
* 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 a non-zero, odd number used as the initial value
* @param multiplierNonZeroOddNumber a non-zero, odd number used as the multiplier
* @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, false);
}
/**
* This method uses reflection to build a valid hash code.
* <p>
* 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.
* Static fields will not be tested.
* <p>
* 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())) {
if (!Modifier.isStatic(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;
}
}
⏎ org/apache/commons/lang/builder/HashCodeBuilder.java
⇒ Using commons-lang3.jar in Java Programs
⇐ commons-lang-2.6.jar - Apache Commons Lang
2017-04-15, 18761👍, 0💬
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