com.jn.langx.util

类 Maths.HashMaths

java.lang.Object

com.jn.langx.util.Maths.HashMaths

封闭类:

Maths

public static final class Maths.HashMaths
extends Object

从以下版本开始:

4.1.0

方法概要

限定符和类型	方法和说明
static int	multiHashOrdered(int accumulatedHash, int nextHash) A hash function which combines an accumulated hash with a next hash such that f(f(k, b), a) ≠ₙ f(f(k, a), b).
static int	multiHashOrdered(int accumulatedHash, int prime, int nextHash) A hash function which combines an accumulated hash with a next hash such that f(f(k, p2, b), p1, a) ≠ₙ f(f(k, p1, a), p2, b).
static int	multiHashUnordered(int accumulatedHash, int nextHash) A hash function which combines an accumulated hash with a next hash such that f(f(k, b), a) = f(f(k, a), b).
static int	multiHashUnordered(int accumulatedHash, int prime, int nextHash) A hash function which combines an accumulated hash with a next hash such that f(f(k, p2, b), p1, a) = f(f(k, p1, a), p2, b).
static int	multiplyWrap(int a, int b) Multiply two unsigned integers together.
static int	roundToPowerOfTwo(int value) Round the given value up to the next positive power of two.

从类继承的方法 java.lang.Object

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

方法详细资料

roundToPowerOfTwo

public static int roundToPowerOfTwo(int value)

Round the given value up to the next positive power of two.

参数:

value - the value (must not be negative and must be less than or equal to 2^31)

返回:

the rounded power of two value

multiHashOrdered

public static int multiHashOrdered(int accumulatedHash,
                                   int prime,
                                   int nextHash)

A hash function which combines an accumulated hash with a next hash such that f(f(k, p2, b), p1, a) ≠ₙ f(f(k, p1, a), p2, b). This function is suitable for object chains whose order affects the overall equality of the hash code.

The exact algorithm is not specified and is therefore subject to change and should not be relied upon for hash codes that persist outside of the JVM process.

参数:

accumulatedHash - the accumulated hash code of the previous stage

prime - a prime multiplier

nextHash - the hash code of the next single item

返回:

the new accumulated hash code

multiHashUnordered

public static int multiHashUnordered(int accumulatedHash,
                                     int prime,
                                     int nextHash)

A hash function which combines an accumulated hash with a next hash such that f(f(k, p2, b), p1, a) = f(f(k, p1, a), p2, b). This function is suitable for object chains whose order does not affect the overall equality of the hash code.

The exact algorithm is not specified and is therefore subject to change and should not be relied upon for hash codes that persist outside of the JVM process.

参数:

accumulatedHash - the accumulated hash code of the previous stage

prime - a prime multiplier

nextHash - the hash code of the next single item

返回:

the new accumulated hash code

multiHashOrdered

public static int multiHashOrdered(int accumulatedHash,
                                   int nextHash)

A hash function which combines an accumulated hash with a next hash such that f(f(k, b), a) ≠ₙ f(f(k, a), b). This function is suitable for object chains whose order affects the overall equality of the hash code.

The exact algorithm is not specified and is therefore subject to change and should not be relied upon for hash codes that persist outside of the JVM process.

参数:

accumulatedHash - the accumulated hash code of the previous stage

nextHash - the hash code of the next single item

返回:

the new accumulated hash code

multiHashUnordered

public static int multiHashUnordered(int accumulatedHash,
                                     int nextHash)

A hash function which combines an accumulated hash with a next hash such that f(f(k, b), a) = f(f(k, a), b). This function is suitable for object chains whose order does not affect the overall equality of the hash code.

The exact algorithm is not specified and is therefore subject to change and should not be relied upon for hash codes that persist outside of the JVM process.

参数:

accumulatedHash - the accumulated hash code of the previous stage

nextHash - the hash code of the next single item

返回:

the new accumulated hash code

multiplyWrap

public static int multiplyWrap(int a,
                               int b)

Multiply two unsigned integers together. If the result overflows a 32-bit number, XOR the overflowed bits back into the result. This operation is commutative, i.e. if we designate the ⨰ symbol to represent this operation, then a ⨰ b = b ⨰ a. This operation is not associative, i.e. (a ⨰ b) ⨰ c ≠ₙ a ⨰ (b ⨰ c) (the symbol ≠ₙ meaning "not necessarily equal to"), therefore this operation is suitable for ordered combinatorial hash functions.

参数:

a - the first number to multiply

b - the second number to multiply

返回:

the wrapped multiply result