Null Safe Hash Code : Hash Code « Development Class « Java
Null Safe Hash Code
import java.lang.reflect.Array;
import java.util.Arrays;
/*
* Copyright 2002-2007 the original author or authors.
*
* 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.
*/
//Revised from springframework
/**
* Miscellaneous object utility methods. Mainly for internal use within the
* framework; consider Jakarta's Commons Lang for a more comprehensive suite
* of object utilities.
*
* @author Juergen Hoeller
* @author Keith Donald
* @author Rod Johnson
* @author Rob Harrop
* @author Alex Ruiz
* @since 19.03.2004
* @see org.apache.commons.lang.ObjectUtils
*/
abstract class ObjectUtils {
private static final int INITIAL_HASH = 7;
private static final int MULTIPLIER = 31;
private static final String EMPTY_STRING = "";
private static final String NULL_STRING = "null";
private static final String ARRAY_START = "{";
private static final String ARRAY_END = "}";
private static final String EMPTY_ARRAY = ARRAY_START + ARRAY_END;
private static final String ARRAY_ELEMENT_SEPARATOR = ", ";
/**
* Return a hash code based on the contents of the specified array.
* If <code>array</code> is <code>null</code>, this method returns 0.
*/
public static int nullSafeHashCode(boolean[] array) {
if (array == null) {
return 0;
}
int hash = INITIAL_HASH;
int arraySize = array.length;
for (int i = 0; i < arraySize; i++) {
hash = MULTIPLIER * hash + hashCode(array[i]);
}
return hash;
}
/**
* Return a hash code based on the contents of the specified array.
* If <code>array</code> is <code>null</code>, this method returns 0.
*/
public static int nullSafeHashCode(byte[] array) {
if (array == null) {
return 0;
}
int hash = INITIAL_HASH;
int arraySize = array.length;
for (int i = 0; i < arraySize; i++) {
hash = MULTIPLIER * hash + array[i];
}
return hash;
}
/**
* Return a hash code based on the contents of the specified array.
* If <code>array</code> is <code>null</code>, this method returns 0.
*/
public static int nullSafeHashCode(char[] array) {
if (array == null) {
return 0;
}
int hash = INITIAL_HASH;
int arraySize = array.length;
for (int i = 0; i < arraySize; i++) {
hash = MULTIPLIER * hash + array[i];
}
return hash;
}
/**
* Return a hash code based on the contents of the specified array.
* If <code>array</code> is <code>null</code>, this method returns 0.
*/
public static int nullSafeHashCode(double[] array) {
if (array == null) {
return 0;
}
int hash = INITIAL_HASH;
int arraySize = array.length;
for (int i = 0; i < arraySize; i++) {
hash = MULTIPLIER * hash + hashCode(array[i]);
}
return hash;
}
/**
* Return a hash code based on the contents of the specified array.
* If <code>array</code> is <code>null</code>, this method returns 0.
*/
public static int nullSafeHashCode(float[] array) {
if (array == null) {
return 0;
}
int hash = INITIAL_HASH;
int arraySize = array.length;
for (int i = 0; i < arraySize; i++) {
hash = MULTIPLIER * hash + hashCode(array[i]);
}
return hash;
}
/**
* Return a hash code based on the contents of the specified array.
* If <code>array</code> is <code>null</code>, this method returns 0.
*/
public static int nullSafeHashCode(int[] array) {
if (array == null) {
return 0;
}
int hash = INITIAL_HASH;
int arraySize = array.length;
for (int i = 0; i < arraySize; i++) {
hash = MULTIPLIER * hash + array[i];
}
return hash;
}
/**
* Return a hash code based on the contents of the specified array.
* If <code>array</code> is <code>null</code>, this method returns 0.
*/
public static int nullSafeHashCode(long[] array) {
if (array == null) {
return 0;
}
int hash = INITIAL_HASH;
int arraySize = array.length;
for (int i = 0; i < arraySize; i++) {
hash = MULTIPLIER * hash + hashCode(array[i]);
}
return hash;
}
/**
* Return a hash code based on the contents of the specified array.
* If <code>array</code> is <code>null</code>, this method returns 0.
*/
public static int nullSafeHashCode(short[] array) {
if (array == null) {
return 0;
}
int hash = INITIAL_HASH;
int arraySize = array.length;
for (int i = 0; i < arraySize; i++) {
hash = MULTIPLIER * hash + array[i];
}
return hash;
}
/**
* Return the same value as <code>{@link Boolean#hashCode()}</code>.
* @see Boolean#hashCode()
*/
public static int hashCode(boolean bool) {
return bool ? 1231 : 1237;
}
/**
* Return the same value as <code>{@link Double#hashCode()}</code>.
* @see Double#hashCode()
*/
public static int hashCode(double dbl) {
long bits = Double.doubleToLongBits(dbl);
return hashCode(bits);
}
/**
* Return the same value as <code>{@link Float#hashCode()}</code>.
* @see Float#hashCode()
*/
public static int hashCode(float flt) {
return Float.floatToIntBits(flt);
}
/**
* Return the same value as <code>{@link Long#hashCode()}</code>.
* @see Long#hashCode()
*/
public static int hashCode(long lng) {
return (int) (lng ^ (lng >>> 32));
}
}
