Mega Code Archive
A hash-code generator and a collection of static hash-code generation methods
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/*
* JBoss, Home of Professional Open Source
* Copyright 2005, JBoss Inc., and individual contributors as indicated
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
import java.io.Serializable;
/**
* A hash-code generator and a collection of static hash-code generation
* methods.
*
* @version <tt>$Revision: 2800 $</tt>
* @author <a href="mailto:jason@planet57.com">Jason Dillon</a>
*/
@SuppressWarnings("unchecked")
public final class HashCode implements Serializable, Cloneable, Comparable {
/** The serialVersionUID */
private static final long serialVersionUID = 2391396931740264021L;
/** Hashcode for a 'null' value. */
private static final int NULL_HASHCODE = 0;
/** Hashcode for a 'true' boolean */
private static final int TRUE_HASHCODE = 1231; // completely arbitrary
/** Hashcode for a 'false' boolean */
private static final int FALSE_HASHCODE = 1237; // completely arbitrary
/** The hash-code value. */
private int value;
/**
* Construct a new <tt>HashCode</tt> using the given <tt>int</tt> as the
* base value.
*
* @param value
* <tt>int</tt> to use as the base value.
*/
public HashCode(final int value) {
this.value = value;
}
/**
* Construct a new <tt>HashCode</tt>.
*/
public HashCode() {
this(0);
}
/**
* Add the hash-code of the given value.
*
* @param b
* Value to get hash-code from.
* @return <i>This</i> <tt>HashCode</tt>.
*/
public HashCode add(final boolean b) {
value ^= generate(b);
return this;
}
/**
* Add the hash-code of the given value.
*
* @param n
* Value to get hash-code from.
* @return <i>This</i> <tt>HashCode</tt>.
*/
public HashCode add(final byte n) {
value ^= n;
return this;
}
/**
* Add the hash-code of the given value.
*
* @param n
* Value to get hash-code from.
* @return <i>This</i> <tt>HashCode</tt>.
*/
public HashCode add(final char n) {
value ^= n;
return this;
}
/**
* Add the hash-code of the given value.
*
* @param n
* Value to get hash-code from.
* @return <i>This</i> <tt>HashCode</tt>.
*/
public HashCode add(final short n) {
value ^= n;
return this;
}
/**
* Add the hash-code of the given value.
*
* @param n
* Value to get hash-code from.
* @return <i>This</i> <tt>HashCode</tt>.
*/
public HashCode add(final int n) {
value ^= n;
return this;
}
/**
* Add the hash-code of the given value.
*
* @param n
* Value to get hash-code from.
* @return <i>This</i> <tt>HashCode</tt>.
*/
public HashCode add(final long n) {
value ^= generate(n);
return this;
}
/**
* Add the hash-code of the given value.
*
* @param f
* Value to get hash-code from.
* @return <i>This</i> <tt>HashCode</tt>.
*/
public HashCode add(final float f) {
value ^= generate(f);
return this;
}
/**
* Add the hash-code of the given value.
*
* @param f
* Value to get hash-code from.
* @return <i>This</i> <tt>HashCode</tt>.
*/
public HashCode add(final double f) {
value ^= generate(f);
return this;
}
/**
* Add the hash-code of the given object.
*
* @param obj
* Value to get hash-code from.
* @return <i>This</i> <tt>HashCode</tt>.
*/
public HashCode add(final Object obj) {
value ^= generate(obj);
return this;
}
/**
* Get the hash-code.
*
* @return Hash-code.
*/
public int hashCode() {
return value;
}
/**
* Compares this object with the specified <tt>int</tt> for order.
*
* @param other
* Value to compare with.
* @return A negative integer, zero, or a positive integer as this object is
* less than, equal to, or greater than the specified object.
*/
public int compareTo(final int other) {
return (value < other) ? -1 : (value == other) ? 0 : 1;
}
/**
* Compares this object with the specified object for order.
*
* @param obj
* Value to compare with.
* @return A negative integer, zero, or a positive integer as this object is
* less than, equal to, or greater than the specified object.
*
* @throws ClassCastException
* Object is not a <tt>HashCode</tt>.
*/
public int compareTo(final Object obj) throws ClassCastException {
HashCode hashCode = (HashCode) obj;
return compareTo(hashCode.value);
}
/**
* Test the equality of this <tt>HashCode</tt> and another object.
*
* @param obj
* Object to test equality with.
* @return True if object is equal.
*/
public boolean equals(final Object obj) {
if (obj == this)
return true;
if (obj != null && obj.getClass() == getClass()) {
return value == ((HashCode) obj).value;
}
return false;
}
/**
* Return a string representation of this <tt>HashCode</tt>.
*
* @return A string representation of this <tt>HashCode</tt>.
*/
public String toString() {
return String.valueOf(value);
}
/**
* Return a cloned copy of this <tt>HashCode</tt>.
*
* @return Cloned <tt>HashCode</tt>.
*/
public Object clone() {
try {
return super.clone();
} catch (CloneNotSupportedException e) {
throw new InternalError();
}
}
// ///////////////////////////////////////////////////////////////////////
// Generation Methods //
// ///////////////////////////////////////////////////////////////////////
/**
* Generate a hash code for a boolean value.
*
* @param value
* Boolean value to generate hash code from.
* @return Hash code.
*/
public static int generate(final boolean value) {
return value ? TRUE_HASHCODE : FALSE_HASHCODE;
}
/**
* Generate a hash code for a long value.
*
* @param value
* Long value to generate hash code from.
* @return Hash code.
*/
public static int generate(final long value) {
return (int) (value ^ (value >> 32));
}
/**
* Generate a hash code for a double value.
*
* @param value
* Double value to generate hash code from.
* @return Hash code.
*/
public static int generate(final double value) {
return generate(Double.doubleToLongBits(value));
}
/**
* Generate a hash code for a float value.
*
* @param value
* Float value to generate hash code from.
* @return Hash code.
*/
public static int generate(final float value) {
return Float.floatToIntBits(value);
}
/**
* Generate a hash code for a byte array.
*
* @param bytes
* An array of bytes to generate a hash code from.
* @return Hash code.
*/
public static int generate(final byte[] bytes) {
int hashcode = 0;
for (int i = 0; i < bytes.length; i++) {
hashcode <<= 1;
hashcode ^= bytes[i];
}
return hashcode;
}
/**
* Generate a hash code for an object array.
*
* <p>
* Does not handle nested primitive array elements.
*
* @param array
* Array to generate hashcode for.
* @param deep
* True to traverse elements which are arrays to determine the
* elements hash code.
* @return Hash code.
*/
public static int generate(final Object array[], final boolean deep) {
int hashcode = 0;
for (int i = 0; i < array.length; i++) {
if (deep && (array[i] instanceof Object[])) {
hashcode ^= generate((Object[]) array[i], true);
} else {
hashcode ^= array[i].hashCode();
}
}
return hashcode;
}
/**
* Generate a shallow hash code for an object array.
*
* @param array
* Array to generate hashcode for.
* @return Hash code.
*/
public static int generate(final Object array[]) {
return generate(array, false);
}
/**
* Generate a hash code for an object.
*
* @param obj
* Object to generate hashcode for.
* @return Hash code.
*/
public static int generate(final Object obj) {
if (obj != null) {
return obj.hashCode();
}
return NULL_HASHCODE;
}
}
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