org.deduced.utilities
Class HashCodeUtilities

java.lang.Object
  org.deduced.utilities.HashCodeUtilities

public final class HashCodeUtilities
extends java.lang.Object

Collected methods which allow easy implementation of hashCode. Example use case:

 public int hashCode()
 {
        int result = HashCodeUtilities.SEED;
        //collect the contributions of various fields
        result = HashCodeUtilities.hash(result, fPrimitive);
        result = HashCodeUtilities.hash(result, fObject);
        result = HashCodeUtilities.hash(result, fArray);
        return result;
 }
 

Author:

Steve McDuff

Field Summary

private static int	INITIAL_PRIME_NUMBER a random prime number to use when merging hash codes
static int	INTEGER_BIT_COUNT bit count of a Integer
static int	SEED An initial value for a hashCode, to which is added contributions from fields.

Constructor Summary

HashCodeUtilities()

Method Summary

private static int	firstTerm(int aSeed) modify the hash code for merging
static int	hash(int aSeed, boolean aBoolean) merge hash code with a boolean.
static int	hash(int aSeed, char aChar) merge hash code with a char.
static int	hash(int aSeed, double aDouble) merge hash code with a double.
static int	hash(int aSeed, float aFloat) merge hash code with a float.
static int	hash(int aSeed, int aInt) merge hash code with a int.
static int	hash(int aSeed, long aLong) merge hash code with a long.
static int	hash(int aSeed, java.lang.Object aObject) merge hash code with a java object.
private static boolean	isArray(java.lang.Object aObject) test if an object is an array

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

INTEGER_BIT_COUNT

public static final int INTEGER_BIT_COUNT

bit count of a Integer

See Also:

Constant Field Values

SEED

public static final int SEED

An initial value for a hashCode, to which is added contributions from fields. Using a non-zero value decreases collisions of hashCode values.

See Also:

Constant Field Values

INITIAL_PRIME_NUMBER

private static final int INITIAL_PRIME_NUMBER

a random prime number to use when merging hash codes

See Also:

Constant Field Values

Constructor Detail

HashCodeUtilities

public HashCodeUtilities()

Method Detail

hash

public static int hash(int aSeed,
                       boolean aBoolean)

merge hash code with a boolean.

Parameters:

aSeed - the seed hash code

aBoolean - the boolean value

Returns:

the boolean hash code

hash

public static int hash(int aSeed,
                       char aChar)

merge hash code with a char.

Parameters:

aSeed - the seed hash code

aChar - the char value

Returns:

the merged hash code

hash

public static int hash(int aSeed,
                       int aInt)

merge hash code with a int.

Parameters:

aSeed - the seed hash code

aInt - the int value

Returns:

the merged hash code

hash

public static int hash(int aSeed,
                       long aLong)

merge hash code with a long.

Parameters:

aSeed - the seed hash code

aLong - the long value

Returns:

the merged hash code

hash

public static int hash(int aSeed,
                       float aFloat)

merge hash code with a float.

Parameters:

aSeed - the seed hash code

aFloat - the float value

Returns:

the merged hash code

hash

public static int hash(int aSeed,
                       double aDouble)

merge hash code with a double.

Parameters:

aSeed - the seed hash code

aDouble - the double value

Returns:

the merged hash code

hash

public static int hash(int aSeed,
                       java.lang.Object aObject)

merge hash code with a java object. aObject is a possibly-null object field, and possibly an array. If aObject is an array, then each element may be a primitive or a possibly-null object.

Parameters:

aSeed - the seed hash code

aObject - the object

Returns:

the merged hash code

firstTerm

private static int firstTerm(int aSeed)

modify the hash code for merging

Parameters:

aSeed - the current hash code

Returns:

the hash code ready to be merged

isArray

private static boolean isArray(java.lang.Object aObject)

test if an object is an array

Parameters:

aObject - the object to test

Returns:

true if the object is an array