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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.
*/
package org.jboss.ws.core.utils;
import java.lang.reflect.Array;
/**
* Collected methods which allow easy implementation of <code>hashCode</code>.
*
* Example use case:
* <pre>
* public int hashCode(){
* int result = HashCodeUtil.SEED;
* //collect the contributions of various fields
* result = HashCodeUtil.hash(result, fPrimitive);
* result = HashCodeUtil.hash(result, fObject);
* result = HashCodeUtil.hash(result, fArray);
* return result;
* }
* </pre>
*/
public final class HashCodeUtil
{
/**
* An initial value for a <code>hashCode</code>, to which is added contributions
* from fields. Using a non-zero value decreases collisons of <code>hashCode</code>
* values.
*/
public static final int SEED = 23;
/**
* booleans.
*/
public static int hash(int aSeed, boolean aBoolean)
{
return org.jboss.ws.core.utils.HashCodeUtil.firstTerm(aSeed) + (aBoolean ? 1 : 0);
}
/**
* chars.
*/
public static int hash(int aSeed, char aChar)
{
return org.jboss.ws.core.utils.HashCodeUtil.firstTerm(aSeed) + (int)aChar;
}
/**
* ints.
*/
public static int hash(int aSeed, int aInt)
{
/*
* Implementation Note
* Note that byte and short are handled by this method, through
* implicit conversion.
*/
return org.jboss.ws.core.utils.HashCodeUtil.firstTerm(aSeed) + aInt;
}
/**
* longs.
*/
public static int hash(int aSeed, long aLong)
{
return org.jboss.ws.core.utils.HashCodeUtil.firstTerm(aSeed) + (int)(aLong ^ (aLong >>> 32));
}
/**
* floats.
*/
public static int hash(int aSeed, float aFloat)
{
return org.jboss.ws.core.utils.HashCodeUtil.hash(aSeed, Float.floatToIntBits(aFloat));
}
/**
* doubles.
*/
public static int hash(int aSeed, double aDouble)
{
return org.jboss.ws.core.utils.HashCodeUtil.hash(aSeed, Double.doubleToLongBits(aDouble));
}
/**
* <code>aObject</code> is a possibly-null object field, and possibly an array.
*
* If <code>aObject</code> is an array, then each element may be a primitive
* or a possibly-null object.
*/
public static int hash(int aSeed, Object aObject)
{
int result = aSeed;
if (aObject == null)
{
result = org.jboss.ws.core.utils.HashCodeUtil.hash(result, 0);
}
else if (!org.jboss.ws.core.utils.HashCodeUtil.isArray(aObject))
{
result = org.jboss.ws.core.utils.HashCodeUtil.hash(result, aObject.hashCode());
}
else
{
int length = Array.getLength(aObject);
for (int idx = 0; idx < length; ++idx)
{
Object item = Array.get(aObject, idx);
//recursive call!
result = org.jboss.ws.core.utils.HashCodeUtil.hash(result, item);
}
}
return result;
}
/// PRIVATE ///
private static final int fODD_PRIME_NUMBER = 37;
private static int firstTerm(int aSeed)
{
return org.jboss.ws.core.utils.HashCodeUtil.fODD_PRIME_NUMBER * aSeed;
}
private static boolean isArray(Object aObject)
{
return aObject.getClass().isArray();
}
}
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