Package org.apache.juneau.commons.lang

Class HashCode

java.lang.Object

org.apache.juneau.commons.lang.HashCode

public class HashCode
extends Object

Utility class for generating integer hash codes.

General usage:

int hashCode = HashCode.create().add("foobar").add(myobject).add(123).get();

Constructor Summary

Constructors

Constructor	Description
HashCode()

Method Summary

Modifier and Type	Method	Description
HashCode	add(int i)	Hashes the hashcode into this object.
HashCode	add(Object o)	Hashes the hashcode of the specified object into this object.
static final HashCode	create()	Create a new HashCode object.
int	get()	Return the calculated hashcode value.
static final int	of(Object... objects)	Calculates a hash code over the specified objects.
protected Object	unswap(Object o)	Converts the object to a normalized form before grabbing it's hashcode.

Methods inherited from class java.lang.Object

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

Constructor Details

HashCode

public HashCode()

Method Details

create

public static final HashCode create()

Create a new HashCode object.

Returns:

A new HashCode object.

of

public static final int of(Object... objects)

Calculates a hash code over the specified objects.

Uses the same algorithm as Objects.hash(Object...) (31 * result + element hash).

Special handling is provided for:

• Annotations: Uses AnnotationUtils.hash(Annotation) to ensure consistent hashing according to the Annotation.hashCode() contract.
• Arrays: Uses content-based hashing via Arrays.hashCode(Object[]) instead of identity-based hashing.
• Null values: Treated as 0 in the hash calculation.

Parameters:

objects - The objects to calculate a hashcode over.

Returns:

A numerical hashcode value.

See Also:

• add(Object)
• AnnotationUtils.hash(Annotation)
• Objects.hash(Object...)

add

public HashCode add(int i)

Hashes the hashcode into this object.

The formula is simply hashCode = 31*hashCode + i;

Parameters:

i - The hashcode to hash into this object's hashcode.

Returns:

This object.

add

public HashCode add(Object o)

Hashes the hashcode of the specified object into this object.

The formula is hashCode = 31*hashCode + elementHash;

Special handling is provided for:

• Null values: Adds 0 to the hash code.
• Annotations: Uses AnnotationUtils.hash(Annotation) to ensure consistent hashing according to the Annotation.hashCode() contract.
• Arrays: Uses content-based hashing via Arrays.hashCode(Object[]) instead of identity-based hashing. Supports all primitive array types and object arrays.
• Other objects: Uses the object's Object.hashCode() method.

Parameters:

o - The object whose hashcode will be hashed with this object.

Returns:

This object.

See Also:

• AnnotationUtils.hash(Annotation)
• Arrays.hashCode(Object[])

get

public int get()

Return the calculated hashcode value.

Returns:

The calculated hashcode.

unswap

protected Object unswap(Object o)

Converts the object to a normalized form before grabbing it's hashcode.

Subclasses can override this method to provide specialized handling (e.g. converting numbers to strings so that 123 and "123" end up creating the same hashcode.)

Default implementation does nothing.

Parameters:

o - The object to normalize before getting it's hashcode.

Returns:

The normalized object.