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com.tangosol.util
Class NullImplementation.NullSet

java.lang.Object
java.util.AbstractCollection
java.util.AbstractSet
com.tangosol.util.NullImplementation.NullSet

All Implemented Interfaces:

ExternalizableLite, PortableObject, Serializable, Iterable, Collection, Set

Enclosing class:

NullImplementation

public static class NullImplementation.NullSet

extends AbstractSet

implements Serializable, ExternalizableLite, PortableObject

An immutable set which contains nothing.

Field Summary

static Set

INSTANCE Since the set contains no information, only one ever has to exist.

Constructor Summary

NullImplementation.NullSet()
Default constructor (for ExternalizableLite and PortableObject).

Method Summary

boolean	add(Object o) Ensures that this Collection contains the specified element.
void	clear() Removes all of the elements from this Collection.
boolean	contains(Object o) Returns true if this Collection contains the specified element.
boolean	equals(Object o) Compares the specified object with this set for equality.
int	hashCode() Returns the hash code value for this set.
Iterator	iterator() Returns an Iterator over the elements contained in this Collection.
void	readExternal(DataInput in) Restore the contents of this object by loading the object's state from the passed DataInput object.
void	readExternal(PofReader in) Restore the contents of a user type instance by reading its state using the specified PofReader object.
boolean	remove(Object o) Removes a single instance of the specified element from this Collection, if it is present (optional operation).
int	size() Returns the number of elements in this Collection.
Object[]	toArray() Returns an array containing all of the elements in this Set.
void	writeExternal(DataOutput out) Save the contents of this object by storing the object's state into the passed DataOutput object.
void	writeExternal(PofWriter out) Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Methods inherited from class java.util.AbstractSet

removeAll

Methods inherited from class java.util.AbstractCollection

addAll, containsAll, isEmpty, retainAll, toArray, toString

Methods inherited from interface java.util.Set

addAll, containsAll, isEmpty, retainAll, toArray

Field Detail

INSTANCE

public static final Set INSTANCE

Since the set contains no information, only one ever has to exist.

Constructor Detail

NullImplementation.NullSet

public NullImplementation.NullSet()

Default constructor (for ExternalizableLite and PortableObject).

Method Detail

toArray

public Object[] toArray()

Returns an array containing all of the elements in this Set. Obeys the general contract of Collection.toArray.

Specified by:

toArray in interface Collection

Specified by:

toArray in interface Set

Overrides:

toArray in class AbstractCollection

Returns:

an Object array containing all of the elements in this Set

iterator

public Iterator iterator()

Returns an Iterator over the elements contained in this Collection.

Specified by:

iterator in interface Iterable

Specified by:

iterator in interface Collection

Specified by:

iterator in interface Set

Specified by:

iterator in class AbstractCollection

Returns:

an Iterator over the elements contained in this Collection

size

public int size()

Returns the number of elements in this Collection.

Specified by:

size in interface Collection

Specified by:

size in interface Set

Specified by:

size in class AbstractCollection

Returns:

the number of elements in this Collection

contains

public boolean contains(Object o)

Returns true if this Collection contains the specified element. More formally, returns true if and only if this Collection contains at least one element e such that (o==null ? e==null : o.equals(e)).

Specified by:

contains in interface Collection

Specified by:

contains in interface Set

Overrides:

contains in class AbstractCollection

Parameters:

o - the object to search for in the set

Returns:

true if this set contains the specified object

add

public boolean add(Object o)

Ensures that this Collection contains the specified element.

Specified by:

add in interface Collection

Specified by:

add in interface Set

Overrides:

add in class AbstractCollection

Parameters:

o - element whose presence in this Collection is to be ensured

Returns:

true if the Collection changed as a result of the call

remove

public boolean remove(Object o)

Removes a single instance of the specified element from this Collection, if it is present (optional operation). More formally, removes an element e such that (o==null ? e==null : o.equals(e)), if the Collection contains one or more such elements. Returns true if the Collection contained the specified element (or equivalently, if the Collection changed as a result of the call).

Specified by:

remove in interface Collection

Specified by:

remove in interface Set

Overrides:

remove in class AbstractCollection

Parameters:

o - element to be removed from this Collection, if present

Returns:

true if the Collection contained the specified element

clear

public void clear()

Removes all of the elements from this Collection.

Specified by:

clear in interface Collection

Specified by:

clear in interface Set

Overrides:

clear in class AbstractCollection

equals

public boolean equals(Object o)

Description copied from class: java.util.AbstractSet

Compares the specified object with this set for equality. Returns true if the given object is also a set, the two sets have the same size, and every member of the given set is contained in this set. This ensures that the equals method works properly across different implementations of the Set interface.

This implementation first checks if the specified object is this set; if so it returns true. Then, it checks if the specified object is a set whose size is identical to the size of this set; if not, it returns false. If so, it returns containsAll((Collection) o).

Specified by:

equals in interface Collection

Specified by:

equals in interface Set

Overrides:

equals in class AbstractSet

Parameters:

o - Object to be compared for equality with this set.

Returns:

true if the specified object is equal to this set.

See Also:

Object.equals(Object), Set.equals(Object), List.equals(Object)

hashCode

public int hashCode()

Description copied from class: java.util.AbstractSet

Returns the hash code value for this set. The hash code of a set is defined to be the sum of the hash codes of the elements in the set. This ensures that s1.equals(s2) implies that s1.hashCode()==s2.hashCode() for any two sets s1 and s2, as required by the general contract of Object.hashCode.

This implementation enumerates over the set, calling the hashCode method on each element in the collection, and adding up the results.

Specified by:

hashCode in interface Collection

Specified by:

hashCode in interface Set

Overrides:

hashCode in class AbstractSet

Returns:

the hash code value for this set.

See Also:

Object.hashCode(), Object.equals(Object)

readExternal

public void readExternal(DataInput in)
                  throws IOException

Restore the contents of this object by loading the object's state from the passed DataInput object.

Specified by:

readExternal in interface ExternalizableLite

Parameters:

in - the DataInput stream to read data from in order to restore the state of this object

Throws:

IOException - if an I/O exception occurs

NotActiveException - if the object is not in its initial state, and therefore cannot be deserialized into

writeExternal

public void writeExternal(DataOutput out)
                   throws IOException

Save the contents of this object by storing the object's state into the passed DataOutput object.

Specified by:

writeExternal in interface ExternalizableLite

Parameters:

out - the DataOutput stream to write the state of this object to

Throws:

IOException - if an I/O exception occurs

readExternal

public void readExternal(PofReader in)
                  throws IOException

Restore the contents of a user type instance by reading its state using the specified PofReader object.

Specified by:

readExternal in interface PortableObject

Parameters:

in - the PofReader from which to read the object's state

Throws:

IOException - if an I/O error occurs

writeExternal

public void writeExternal(PofWriter out)
                   throws IOException

Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Specified by:

writeExternal in interface PortableObject

Parameters:

out - the PofWriter to which to write the object's state

Throws:

IOException - if an I/O error occurs

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