Package org.apache.sis.metadata

Class HashCode

java.lang.Object

org.apache.sis.metadata.MetadataVisitor<Integer>

org.apache.sis.metadata.HashCode

final class HashCode
extends MetadataVisitor<Integer>

Computes a hash code for the specified metadata. The hash code is defined as the sum of hash codes of all non-empty properties, plus the hash code of the interface. This is a similar contract than Set.hashCode() (except for the interface) and ensures that the hash code value is insensitive to the ordering of properties.

Since:

1.0

Version:

1.0

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.sis.metadata.MetadataVisitor

MetadataVisitor.Filter

Field Summary

Fields

Modifier and Type	Field	Description
private int	code	The hash code value, returned by MetadataStandard.hashCode(Object) after calculation.
private static final ThreadLocal<HashCode>	VISITORS	Provider of visitor instances used by MetadataStandard.hashCode(Object).

Fields inherited from class org.apache.sis.metadata.MetadataVisitor

SKIP_SIBLINGS

Constructor Summary

Constructors

Modifier	Constructor	Description
private	HashCode()	Instantiated by VISITORS only.

Method Summary

Modifier and Type	Method	Description
(package private) final ThreadLocal<HashCode>	creator()	Returns the thread-local variable that created this HashCode instance.
(package private) static HashCode	getOrCreate()	Returns the visitor for the current thread if it already exists, or creates a new one otherwise.
(package private) MetadataVisitor.Filter	preVisit(PropertyAccessor accessor)	Resets the hash code to an initial value for a new metadata instance.
(package private) Integer	result()	Returns the hash code result after visiting all elements in a metadata instance.
(package private) Object	visit(Class<?> type, Object value)	Adds the hash code of the given metadata property value.

Methods inherited from class org.apache.sis.metadata.MetadataVisitor

getCurrentPropertyPath, setCurrentProperty, walk

Methods inherited from class java.lang.Object

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

Field Details

VISITORS

private static final ThreadLocal<HashCode> VISITORS

Provider of visitor instances used by MetadataStandard.hashCode(Object).

code

private int code

The hash code value, returned by MetadataStandard.hashCode(Object) after calculation.

Constructor Details

HashCode

private HashCode()

Instantiated by VISITORS only.

Method Details

getOrCreate

static HashCode getOrCreate()

Returns the visitor for the current thread if it already exists, or creates a new one otherwise.

creator

final ThreadLocal<HashCode> creator()

Returns the thread-local variable that created this HashCode instance.

Overrides:

creator in class MetadataVisitor<Integer>

preVisit

MetadataVisitor.Filter preVisit(PropertyAccessor accessor)

Resets the hash code to an initial value for a new metadata instance. If another hash code computation was in progress, that code shall be saved before this method is invoked.

Overrides:

preVisit in class MetadataVisitor<Integer>

Parameters:

accessor - contains the standard interface of the metadata for which a hash code value will be computed.

Returns:

MetadataVisitor.Filter.NON_EMPTY since this visitor is not restricted to writable properties.

visit

Object visit(Class<?> type,
 Object value)

Adds the hash code of the given metadata property value. Invoking this method may cause recursive calls to HashCode methods on this visitor instance if the given value is itself another metadata object.

Specified by:

visit in class MetadataVisitor<Integer>

Parameters:

value - the metadata property value for which to add hash code.

type - the type of elements. Note that this is not necessarily the type of given value argument if the latter is a collection.

Returns:

null, meaning to not modify the metadata property value.

result

Integer result()

Returns the hash code result after visiting all elements in a metadata instance.

Overrides:

result in class MetadataVisitor<Integer>