net.sf.beanlib.util
Class AbstractCollection<E>

java.lang.Object
  net.sf.beanlib.util.AbstractCollection<E>

All Implemented Interfaces:

Iterable<E>, Collection<E>

public abstract class AbstractCollection<E>
extends Object
implements Collection<E>

This class provides a skeletal implementation of the Collection interface, to minimize the effort required to implement this interface.

To implement an unmodifiable collection, the programmer needs only to extend this class and provide implementations for the iterator and size methods. (The iterator returned by the iterator method must implement hasNext and next.)

To implement a modifiable collection, the programmer must additionally override this class's add method (which otherwise throws an UnsupportedOperationException), and the iterator returned by the iterator method must additionally implement its remove method.

The programmer should generally provide a void (no argument) and Collection constructor, as per the recommendation in the Collection interface specification.

The documentation for each non-abstract methods in this class describes its implementation in detail. Each of these methods may be overridden if the collection being implemented admits a more efficient implementation.

This class is a member of the Java Collections Framework.

Since:

1.2

Version:

1.24, 01/18/03

Author:

Josh Bloch, Neal Gafter

See Also:

Collection

Constructor Summary

protected

AbstractCollection() Sole constructor.

Method Summary

boolean	add(E e)
boolean	addAll(Collection<? extends E> c)
void	clear()
boolean	contains(Object o)
boolean	containsAll(Collection<?> c)
boolean	isEmpty()
abstract Iterator<E>	iterator() Returns an iterator over the elements contained in this collection.
boolean	remove(Object o)
boolean	removeAll(Collection<?> c)
boolean	retainAll(Collection<?> c)
abstract int	size()
Object[]	toArray()
<T> T[]	toArray(T[] a)
String	toString() Returns a string representation of this collection.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Collection

equals, hashCode

Constructor Detail

AbstractCollection

protected AbstractCollection()

Sole constructor. (For invocation by subclass constructors, typically implicit.)

Method Detail

iterator

public abstract Iterator<E> iterator()

Returns an iterator over the elements contained in this collection.

Specified by:

iterator in interface Iterable<E>

Specified by:

iterator in interface Collection<E>

Returns:

an iterator over the elements contained in this collection

size

public abstract int size()

Specified by:

size in interface Collection<E>

isEmpty

public boolean isEmpty()

This implementation returns size() == 0.

Specified by:

isEmpty in interface Collection<E>

contains

public boolean contains(Object o)

This implementation iterates over the elements in the collection, checking each element in turn for equality with the specified element.

Specified by:

contains in interface Collection<E>

Throws:

ClassCastException

NullPointerException

toArray

public Object[] toArray()

This implementation allocates the array to be returned, and iterates over the elements in the collection, storing each object reference in the next consecutive element of the array, starting with element 0.

Specified by:

toArray in interface Collection<E>

toArray

public <T> T[] toArray(T[] a)

This implementation checks if the array is large enough to contain the collection; if not, it allocates a new array of the correct size and type (using reflection). Then, it iterates over the collection, storing each object reference in the next consecutive element of the array, starting with element 0. If the array is larger than the collection, a null is stored in the first location after the end of the collection.

Specified by:

toArray in interface Collection<E>

Throws:

ArrayStoreException

NullPointerException

add

public boolean add(E e)

This implementation always throws an UnsupportedOperationException.

Specified by:

add in interface Collection<E>

Throws:

UnsupportedOperationException

ClassCastException

NullPointerException

IllegalArgumentException

IllegalStateException

remove

public boolean remove(Object o)

This implementation iterates over the collection looking for the specified element. If it finds the element, it removes the element from the collection using the iterator's remove method.

Note that this implementation throws an UnsupportedOperationException if the iterator returned by this collection's iterator method does not implement the remove method and this collection contains the specified object.

Specified by:

remove in interface Collection<E>

Throws:

UnsupportedOperationException

ClassCastException

NullPointerException

containsAll

public boolean containsAll(Collection<?> c)

This implementation iterates over the specified collection, checking each element returned by the iterator in turn to see if it's contained in this collection. If all elements are so contained true is returned, otherwise false.

Specified by:

containsAll in interface Collection<E>

Throws:

ClassCastException

NullPointerException

See Also:

contains(Object)

addAll

public boolean addAll(Collection<? extends E> c)

This implementation iterates over the specified collection, and adds each object returned by the iterator to this collection, in turn.

Note that this implementation will throw an UnsupportedOperationException unless add is overridden (assuming the specified collection is non-empty).

Specified by:

addAll in interface Collection<E>

Throws:

UnsupportedOperationException

ClassCastException

NullPointerException

IllegalArgumentException

IllegalStateException

See Also:

add(Object)

removeAll

public boolean removeAll(Collection<?> c)

This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection. If it's so contained, it's removed from this collection with the iterator's remove method.

Note that this implementation will throw an UnsupportedOperationException if the iterator returned by the iterator method does not implement the remove method and this collection contains one or more elements in common with the specified collection.

Specified by:

removeAll in interface Collection<E>

Throws:

UnsupportedOperationException

ClassCastException

NullPointerException

See Also:

remove(Object), contains(Object)

retainAll

public boolean retainAll(Collection<?> c)

This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection. If it's not so contained, it's removed from this collection with the iterator's remove method.

Note that this implementation will throw an UnsupportedOperationException if the iterator returned by the iterator method does not implement the remove method and this collection contains one or more elements not present in the specified collection.

Specified by:

retainAll in interface Collection<E>

Throws:

UnsupportedOperationException

ClassCastException

NullPointerException

See Also:

remove(Object), contains(Object)

clear

public void clear()

This implementation iterates over this collection, removing each element using the Iterator.remove operation. Most implementations will probably choose to override this method for efficiency.

Note that this implementation will throw an UnsupportedOperationException if the iterator returned by this collection's iterator method does not implement the remove method and this collection is non-empty.

Specified by:

clear in interface Collection<E>

Throws:

UnsupportedOperationException

toString

public String toString()

Returns a string representation of this collection. The string representation consists of a list of the collection's elements in the order they are returned by its iterator, enclosed in square brackets ("[]"). Adjacent elements are separated by the characters ", " (comma and space). Elements are converted to strings as by String.valueOf(Object).

Overrides:

toString in class Object

Returns:

a string representation of this collection