speiger.src.collections.utils

Class HashUtil

java.lang.Object

speiger.src.collections.utils.HashUtil

public class HashUtil
extends java.lang.Object

Helper class that is used for HashMap functions reduce duplicated code

Field Summary

Fields

Modifier and Type	Field and Description
static float	DEFAULT_LOAD_FACTOR Default HashMap Load Factor
static int	DEFAULT_MIN_CAPACITY Minimum HashMap Capacity
static int	DEFAULT_MIN_CONCURRENCY Minimum ConcurrentHashMap Concurrency
static float	FAST_LOAD_FACTOR HashMap Load Factor with reduced hash collisions but more memory usage
static float	FASTER_LOAD_FACTOR HashMap Load Factor with minimal hash collisions but more memory usage

Constructor Summary

Constructors

Constructor and Description
HashUtil()

Method Summary

Modifier and Type	Method and Description
static int	arraySize(int size, float loadFactor) Helper function that creates the ideal array size for HashMap
static int	getRequiredBits(int value) Function that finds out how many bits are required to store the number Provided
static int	getRequiredBits(long value) Function that finds out how many bits are required to store the number Provided
static int	invMix(int x) The inverse of mix(int).
static int	mix(int x) Quickly mixes the bits of an integer.
static int	nextPowerOfTwo(int x) Function that rounds up to the closest power of 2 A modified version of https://stackoverflow.com/a/466242
static long	nextPowerOfTwo(long x) Function that rounds up to the closest power of 2 A modified version of https://stackoverflow.com/a/466242

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MIN_CAPACITY

public static final int DEFAULT_MIN_CAPACITY

Minimum HashMap Capacity

See Also:

Constant Field Values

DEFAULT_MIN_CONCURRENCY

public static final int DEFAULT_MIN_CONCURRENCY

Minimum ConcurrentHashMap Concurrency

See Also:

Constant Field Values

DEFAULT_LOAD_FACTOR

public static final float DEFAULT_LOAD_FACTOR

Default HashMap Load Factor

See Also:

Constant Field Values

FAST_LOAD_FACTOR

public static final float FAST_LOAD_FACTOR

HashMap Load Factor with reduced hash collisions but more memory usage

See Also:

Constant Field Values

FASTER_LOAD_FACTOR

public static final float FASTER_LOAD_FACTOR

HashMap Load Factor with minimal hash collisions but more memory usage

See Also:

Constant Field Values

Constructor Detail

HashUtil

public HashUtil()

Method Detail

mix

public static int mix(int x)

Quickly mixes the bits of an integer.

This method mixes the bits of the argument by multiplying by the golden ratio and xorshifting the result. It is borrowed from Koloboke,

Parameters:

x - an integer.

Returns:

a hash value obtained by mixing the bits of x.

See Also:

invMix(int)

invMix

public static int invMix(int x)

The inverse of mix(int). This method is mainly useful to create unit tests.

Parameters:

x - an integer.

Returns:

a value that passed through mix(int) would give x.

nextPowerOfTwo

public static int nextPowerOfTwo(int x)

Function that rounds up to the closest power of 2 A modified version of https://stackoverflow.com/a/466242

Parameters:

x - that should be converted to the next power of two

Returns:

the input number rounded up to the next power of two

nextPowerOfTwo

public static long nextPowerOfTwo(long x)

Function that rounds up to the closest power of 2 A modified version of https://stackoverflow.com/a/466242

Parameters:

x - that should be converted to the next power of two

Returns:

the input number rounded up to the next power of two

getRequiredBits

public static int getRequiredBits(int value)

Function that finds out how many bits are required to store the number Provided

Parameters:

value - to get the required bits to store.

Returns:

the required bits to store that number

Note:

Really useful for compression. Reducing data that is inserted into a GZIP algorithm.

getRequiredBits

public static int getRequiredBits(long value)

Function that finds out how many bits are required to store the number Provided

Parameters:

value - to get the required bits to store.

Returns:

the required bits to store that number

Note:

Really useful for compression. Reducing data that is inserted into a GZIP algorithm.

arraySize

public static int arraySize(int size,
                            float loadFactor)

Helper function that creates the ideal array size for HashMap

Parameters:

size - the original array size

loadFactor - the load factor

Returns:

the new array size