org.josef.util

Class HashUtil

java.lang.Object

org.josef.util.HashUtil

@Status(stage=TEST,
        unitTests=COMPLETE)
 @Review(by="Kees Schotanus",
        at="2009-09-28")
public final class HashUtil
extends Object

Utility class to compute hash codes.
See: Joshua Bloch, Effective Java second edition. Item 9.

Version:

1.0 $Revision: 3753 $

Author:

Kees Schotanus

Field Summary

Fields

Modifier and Type	Field and Description
static int	INITIAL_HASH_CODE Initial hash code value as suggested by Joshua Bloch, Effective Java second edition.
static int	ODD_PRIME_HASH_CODE Value to multiply each individual hash code by, as suggested by Joshua Bloch, Effective Java second edition.

Method Summary

Modifier and Type	Method and Description
static int	computeHashCode(int currentHashCode, boolean value) Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied value, to it.
static int	computeHashCode(int currentHashCode, double value) Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied value, to it.
static int	computeHashCode(int currentHashCode, float value) Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied value, to it.
static int	computeHashCode(int currentHashCode, int value) Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied value, to it.
static int	computeHashCode(int currentHashCode, long value) Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied value, to it.
static int	computeHashCode(int currentHashCode, Object object) Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied object, to it.

Methods inherited from class java.lang.Object

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

Field Detail

INITIAL_HASH_CODE

public static final int INITIAL_HASH_CODE

Initial hash code value as suggested by Joshua Bloch, Effective Java second edition. Item 9.

See Also:

Constant Field Values

ODD_PRIME_HASH_CODE

public static final int ODD_PRIME_HASH_CODE

Value to multiply each individual hash code by, as suggested by Joshua Bloch, Effective Java second edition. Item 9.

See Also:

Constant Field Values

Method Detail

computeHashCode

public static int computeHashCode(int currentHashCode,
                                  boolean value)

Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied value, to it.

Parameters:

currentHashCode - The currently computed hash code.

value - The value to compute the hash code for.

Returns:

Mathematically this method returns: currenthashCode * ODD_PRIME_HASH_CODE + hash code of value.

computeHashCode

public static int computeHashCode(int currentHashCode,
                                  int value)

Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied value, to it.

Parameters:

currentHashCode - The currently computed hash code.

value - The value to compute the hash code for.

Returns:

Mathematically this method returns: currenthashCode * ODD_PRIME_HASH_CODE + hash code of value.

computeHashCode

public static int computeHashCode(int currentHashCode,
                                  long value)

Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied value, to it.

Parameters:

currentHashCode - The currently computed hash code.

value - The value to compute the hash code for.

Returns:

Mathematically this method returns: currenthashCode * ODD_PRIME_HASH_CODE + hash code of value.

computeHashCode

public static int computeHashCode(int currentHashCode,
                                  float value)

Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied value, to it.

Parameters:

currentHashCode - The currently computed hash code.

value - The value to compute the hash code for.

Returns:

Mathematically this method returns: currenthashCode * ODD_PRIME_HASH_CODE + hash code of value.

computeHashCode

public static int computeHashCode(int currentHashCode,
                                  double value)

Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied value, to it.

Parameters:

currentHashCode - The currently computed hash code.

value - The value to compute the hash code for.

Returns:

Mathematically this method returns: currenthashCode * ODD_PRIME_HASH_CODE + hash code of value.

computeHashCode

public static int computeHashCode(int currentHashCode,
                                  Object object)

Multiplies the supplied currentHashCode by ODD_PRIME_HASH_CODE and adds the hash code, computed for the supplied object, to it.

Parameters:

currentHashCode - The currently computed hash code.

object - The object to compute the hash code for.

Returns:

Mathematically this method returns: currenthashCode * ODD_PRIME_HASH_CODE + hash code of object.
When the supplied object is null, zero is used as the hash code, otherwise object.hashCode() is executed.