com.phloc.commons.hash.HashCodeCalculator Maven / Gradle / Ivy
/**
* Copyright (C) 2006-2014 phloc systems
* http://www.phloc.com
* office[at]phloc[dot]com
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.phloc.commons.hash;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;
import com.phloc.commons.CGlobal;
import com.phloc.commons.annotations.PresentForCodeCoverage;
/**
* This class provides the hash code generation for different data types.
*
* @author Philip Helger
*/
@Immutable
public final class HashCodeCalculator
{
/**
* Each value is multiplied with this value. 31 because it can easily be
* optimized to (1 << 5) - 1.
*/
public static final int MULTIPLIER = 31;
/**
* The hash code value to be used for null values. Do not use 0
* as e.g. BigDecimal ("0") also results in a 0 hash code.
*/
public static final int HASHCODE_NULL = 129;
@PresentForCodeCoverage
@SuppressWarnings ("unused")
private static final HashCodeCalculator s_aInstance = new HashCodeCalculator ();
private HashCodeCalculator ()
{}
/**
* Atomic type hash code generation.
*
* @param nPrevHashCode
* The previous hash code used as the basis for calculation
* @param x
* Array to add
* @return The updated hash code
*/
public static int append (final int nPrevHashCode, final boolean x)
{
return append (nPrevHashCode, x ? 1231 : 1237);
}
/**
* Atomic type hash code generation.
*
* @param nPrevHashCode
* The previous hash code used as the basis for calculation
* @param x
* Array to add
* @return The updated hash code
*/
public static int append (final int nPrevHashCode, final byte x)
{
return append (nPrevHashCode, (int) x);
}
/**
* Atomic type hash code generation.
*
* @param nPrevHashCode
* The previous hash code used as the basis for calculation
* @param x
* Array to add
* @return The updated hash code
*/
public static int append (final int nPrevHashCode, final char x)
{
return append (nPrevHashCode, (int) x);
}
/**
* Atomic type hash code generation.
*
* @param nPrevHashCode
* The previous hash code used as the basis for calculation
* @param x
* Array to add
* @return The updated hash code
*/
public static int append (final int nPrevHashCode, final double x)
{
// ESCA-JAVA0078:
return append (nPrevHashCode, x == 0.0 ? 0L : Double.doubleToLongBits (x));
}
/**
* Atomic type hash code generation.
*
* @param nPrevHashCode
* The previous hash code used as the basis for calculation
* @param x
* Array to add
* @return The updated hash code
*/
public static int append (final int nPrevHashCode, final float x)
{
// ESCA-JAVA0078:
return append (nPrevHashCode, x == 0.0F ? 0 : Float.floatToIntBits (x));
}
/**
* Atomic type hash code generation.
*
* @param nPrevHashCode
* The previous hash code used as the basis for calculation
* @param x
* Array to add
* @return The updated hash code
*/
public static int append (final int nPrevHashCode, final int x)
{
return nPrevHashCode * MULTIPLIER + x;
}
/**
* Atomic type hash code generation.
*
* @param nPrevHashCode
* The previous hash code used as the basis for calculation
* @param x
* Array to add
* @return The updated hash code
*/
public static int append (final int nPrevHashCode, final long x)
{
final int nTemp = append (nPrevHashCode, (int) (x >>> CGlobal.BITS_PER_INT));
return append (nTemp, (int) (x & 0xffffffffL));
}
/**
* Atomic type hash code generation.
*
* @param nPrevHashCode
* The previous hash code used as the basis for calculation
* @param x
* Array to add
* @return The updated hash code
*/
public static int append (final int nPrevHashCode, final short x)
{
return append (nPrevHashCode, (int) x);
}
/**
* Object hash code generation.
*
* @param nPrevHashCode
* The previous hash code used as the basis for calculation
* @param x
* Object to add. May be null.
* @return The updated hash code
*/
public static int append (final int nPrevHashCode, @Nullable final Object x)
{
return append (nPrevHashCode, HashCodeImplementationRegistry.getHashCode (x));
}
}