de.frame4j.util

Class PropMap.KeySet<S>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractSet<S>

de.frame4j.util.PropMap.KeySet<S>

All Implemented Interfaces:

Iterable<S>, Collection<S>, Set<S>

Enclosing class:

PropMap

public final class PropMap.KeySet<S>
extends AbstractSet<S>
implements Set<S>

The keys as Set.

An object of this inner class features a set view of the enclosing PropMap's keys.

This KeySet object always mirrors (1:1) the enclosing PropMap's state. For that reason on will get just one (pseudo singleton per PropMap) PropMap.KeySet object no matter how many are requested.

Hint: The seldom used (partly expensive or not recommended) methods AbstractCollection.add(Object) AbstractCollection.addAll(java.util.Collection), AbstractCollection.retainAll(java.util.Collection), AbstractCollection.toArray(Object[]) and AbstractSet.removeAll(java.util.Collection) are unchanged inheritance.


© Copyright 2004 Albrecht Weinert.

Version:

like enclosing class PropMap

Author:

Albrecht Weinert

See Also:

Map.size(), PropMap.size()

Method Summary

Modifier and Type	Method and Description
boolean	add(Object key) Add a new entry (key, null).
void	clear() Delete all keys.
boolean	contains(Object o) Is an object (as key) contained.
boolean	equals(Object other) Equality with other object.
int	hashCode() HashCode (of the PropMap).
boolean	isEmpty() Is the map empty.
Iterator<S>	iterator() An Iterator over all keys.
boolean	remove(Object o) Remove a key.
int	size() Number of keys.
Object[]	toArray() The keys as array.

Methods inherited from class java.util.AbstractSet

removeAll

Methods inherited from class java.util.AbstractCollection

addAll, containsAll, retainAll, toArray, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Set

addAll, containsAll, removeAll, retainAll, spliterator, toArray

Methods inherited from interface java.util.Collection

parallelStream, removeIf, stream

Methods inherited from interface java.lang.Iterable

forEach

Method Detail

size

public int size()

Number of keys.

Specified by:

size in interface Collection<S>

Specified by:

size in interface Set<S>

Specified by:

size in class AbstractCollection<S>

Returns:

PropMap.size()

See Also:

Map.size()

hashCode

public int hashCode()

HashCode (of the PropMap).

Specified by:

hashCode in interface Collection<S>

Specified by:

hashCode in interface Set<S>

Overrides:

hashCode in class AbstractSet<S>

equals

public boolean equals(Object other)

Equality with other object.

Returns true is the enclosing PropMap has the same set of keys as the other object contains Strings respectively CharSequences as set.
This method returns false if the other object is no Set, if its size is not equal to the enclosing PropMap or if it contains anything that is not a CharSequence.

Specified by:

equals in interface Collection<S>

Specified by:

equals in interface Set<S>

Overrides:

equals in class AbstractSet<S>

iterator

public Iterator<S> iterator()

An Iterator over all keys.

This method returns an Iterator over all keys. Even if returning a new Iterator object every time, the call is quite inexpensive.

The returned Iterator's behaviour will get partly unpredictable if the enclosing PropMap changes while using the iterator.

Specified by:

iterator in interface Iterable<S>

Specified by:

iterator in interface Collection<S>

Specified by:

iterator in interface Set<S>

Specified by:

iterator in class AbstractCollection<S>

Returns:

a new Iterator object (anonymous inner class)

isEmpty

public final boolean isEmpty()

Is the map empty.

Specified by:

isEmpty in interface Collection<S>

Specified by:

isEmpty in interface Set<S>

Overrides:

isEmpty in class AbstractCollection<S>

Returns:

false

See Also:

AbstractCollection.isEmpty()

toArray

public Object[] toArray()

The keys as array.

This method returns an array of all keys of the enclosing PropMap. It is dense (contains no null) and is of the actual size.

Specified by:

toArray in interface Collection<S>

Specified by:

toArray in interface Set<S>

Overrides:

toArray in class AbstractCollection<S>

Returns:

an array of String, may be empty, but never null

See Also:

AbstractCollection.toArray()

contains

public boolean contains(Object o)

Is an object (as key) contained.

This method returns true, if o is a non empty CharSequence and is equal to an existing key.

Specified by:

contains in interface Collection<S>

Specified by:

contains in interface Set<S>

Overrides:

contains in class AbstractCollection<S>

Returns:

true if o is a key contained

See Also:

AbstractCollection.contains(java.lang.Object)

clear

public void clear()

Delete all keys.

The effect is a complete clearance of the enclosing PropMap object (by just calling clear()).

Specified by:

clear in interface Collection<S>

Specified by:

clear in interface Set<S>

Overrides:

clear in class AbstractCollection<S>

See Also:

AbstractCollection.clear(), PropMap.clear()

add

public boolean add(Object key)

Add a new entry (key, null).

If the enclosing PropMap did not yet contain an entry with key, it is (in the end by add(key, null)) newly generated and true is returned. This only happens if key is accordance with PropMap's contract.

Is there already an entry (key), it is left unchanged and false is returned.

Specified by:

add in interface Collection<S>

Specified by:

add in interface Set<S>

Overrides:

add in class AbstractCollection<S>

Parameters:

key - the key of the new entry

Returns:

true, if an new entry was added.

Throws:

ClassCastException - if type or value of key violates the contract.

See Also:

PropMap.add(CharSequence, CharSequence), AbstractCollection.add(java.lang.Object)

remove

public boolean remove(Object o)

Remove a key.

If existing, an entry with key o will be removed from the enclosing PropMap.

Specified by:

remove in interface Collection<S>

Specified by:

remove in interface Set<S>

Overrides:

remove in class AbstractCollection<S>

Parameters:

o - the key of the entry to be removed

Returns:

true, in case of a removal

See Also:

AbstractCollection.remove(java.lang.Object)