de.aristaflow.adept2.util

Class HashCalc

java.lang.Object

de.aristaflow.adept2.util.HashCalc

public class HashCalc
extends java.lang.Object

A disposable class to facilitate the calculation of hash codes, i.e. this class is intended to be used in implementations of Object.hashCode().

This class knows how to deal with primitive types and objects, but also arrays (of primitive types and objects), even nested ones. It also deals with order, i.e. feeding it the same values in a different order will also produce a different hash code. null values don't have to be treated specially either.

The initial hash code is based on the class name provided in the constructor. Arbitrary values (usually those that are also queried in Object.equals(Object)) can then be fed to the HashCalc using the various feed(..) methods. The resulting hash code can be retrieved with hashCode().

Constructor Summary

Constructors

Constructor and Description
HashCalc(java.lang.Class<?> forClass) Constructs a new HashCalc for an object of the specified class.

Method Summary

Modifier and Type	Method and Description
boolean	equals(java.lang.Object obj)
static boolean	equals(java.lang.Object first, java.lang.Object second) Compares two values for equality.
HashCalc	feed(boolean value) Feeds a boolean to the computed hash code.
HashCalc	feed(boolean[] array) Feeds a boolean array to the computed hash code.
HashCalc	feed(byte value) Feeds a byte to the computed hash code.
HashCalc	feed(byte[] array) Feeds a byte array to the computed hash code.
HashCalc	feed(char value) Feeds a char to the computed hash code.
HashCalc	feed(double value) Feeds a double to the computed hash code.
HashCalc	feed(double[] array) Feeds a double array to the computed hash code.
HashCalc	feed(float value) Feeds a float to the computed hash code.
HashCalc	feed(float[] array) Feeds a float array to the computed hash code.
HashCalc	feed(int value) Feeds a int to the computed hash code.
HashCalc	feed(int[] array) Feeds a int array to the computed hash code.
HashCalc	feed(long value) Feeds a long value to the computed hash code.
HashCalc	feed(long[] array) Feeds a long array to the computed hash code.
HashCalc	feed(java.lang.Object object) Feeds an Object to the computed hash code.
HashCalc	feed(java.lang.Object[] array) Feeds an Object array to the computed hash code.
HashCalc	feed(short value) Feeds a short to the computed hash code.
HashCalc	feed(short[] array) Feeds a short array to the computed hash code.
HashCalc	feedShallow(java.lang.Object[] array) Feeds an Object array to the computed hash code.
int	hashCode() Returns the computed hash code.

Methods inherited from class java.lang.Object

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

Constructor Detail

HashCalc

public HashCalc(java.lang.Class<?> forClass)

Constructs a new HashCalc for an object of the specified class.

Parameters:

forClass - the type of object for which to calculate a hash code

Method Detail

feed

public HashCalc feed(boolean value)

Feeds a boolean to the computed hash code.

Parameters:

value - value to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(char value)

Feeds a char to the computed hash code.

Parameters:

value - value to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(byte value)

Feeds a byte to the computed hash code.

Parameters:

value - value to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(short value)

Feeds a short to the computed hash code.

Parameters:

value - value to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(int value)

Feeds a int to the computed hash code.

All other feed() methods are redirected to this method. So in order to provide custom hash code computations only this method needs to be overridden.

Parameters:

value - value to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(long value)

Feeds a long value to the computed hash code.

Parameters:

value - value to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(float value)

Feeds a float to the computed hash code.

Parameters:

value - value to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(double value)

Feeds a double to the computed hash code.

Parameters:

value - value to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(java.lang.Object object)

Feeds an Object to the computed hash code. This is done by getting the object's own hash code.

Parameters:

object - object to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(boolean[] array)

Feeds a boolean array to the computed hash code. The arrays hash code is acquired using Arrays.hashCode(boolean[]).

Parameters:

array - array to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(byte[] array)

Feeds a byte array to the computed hash code. The arrays hash code is acquired using Arrays.hashCode(byte[]).

Parameters:

array - array to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(short[] array)

Feeds a short array to the computed hash code. The arrays hash code is acquired using Arrays.hashCode(short[]).

Parameters:

array - array to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(int[] array)

Feeds a int array to the computed hash code. The arrays hash code is acquired using Arrays.hashCode(int[]).

Parameters:

array - array to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(long[] array)

Feeds a long array to the computed hash code. The arrays hash code is acquired using Arrays.hashCode(long[]).

Parameters:

array - array to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(float[] array)

Feeds a float array to the computed hash code. The arrays hash code is acquired using Arrays.hashCode(float[]).

Parameters:

array - array to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(double[] array)

Feeds a double array to the computed hash code. The arrays hash code is acquired using Arrays.hashCode(double[]).

Parameters:

array - array to be included in the hash code

Returns:

this HashCalc

feed

public HashCalc feed(java.lang.Object[] array)

Feeds an Object array to the computed hash code. The array's deep (!) hash code is acquired using Arrays.deepHashCode(Object[]). So be careful if the array could potentially contain direct or indirect references to itself! If you are absolutely sure that the array does not contain any other arrays, using feedShallow(Object[]) may save some instanceofs.

Parameters:

array - array to be included in the hash code

Returns:

this HashCalc

feedShallow

public HashCalc feedShallow(java.lang.Object[] array)

Feeds an Object array to the computed hash code. The array's shallow (!) hash code is acquired using Arrays.hashCode(Object[]). So if the array contains other arrays, their hash code is based on their identity rather than their content. This may be useful if the array could potentially contain direct or indirect references to itself.

Parameters:

array - array to be included in the hash code

Returns:

this HashCalc

hashCode

public int hashCode()

Returns the computed hash code.

Overrides:

hashCode in class java.lang.Object

Returns:

the computed hash code

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

equals

public static boolean equals(java.lang.Object first,
                             java.lang.Object second)

Compares two values for equality. If the first value is null, the second also has to be null. Otherwise equals(Object) is on the first value will be returned.

Parameters:

first - The first value which to check for equality.

second - The second value which to check for equality.

Returns:

Whether the first and the second value are equal with respect to null and equals(Object).