Java in a Nutshell, 5th Edition

Name

CopyOnWriteArrayList<E>

Synopsis

This class is a threadsafe java.util.List implementation based on an array. Any number of read operations may proceed concurrently. All update methods are synchronized and make a completely new copy of the internal array, so this class is best suited to applications in which reads greatly outnumber updates. The Iterator of a CopyOnWriteArrayList operates on the copy of the array that was current when the iterator( ) method was called: it does not see any updates that occur after the call to iterator( ) and is guaranteed never to throw ConcurrentModificationException. Update methods of the Iterator and ListIterator interfaces are not supported and throw UnsupportedOperationException.

CopyOnWriteArrayList defines a few useful methods beyond those specified by the List interface. addIfAbsent( ) atomically adds an element to the list, but only if the list does not already contain that element. addAllAbsent( ) adds all elements of a collection that are not already in the list. Two new indexOf( ) and lastIndexOf( ) methods are defined that specify a starting index for the search. These provide a convenient alternative to using a subList( ) view when searching for repeated matches in a list.

Figure 16-78. java.util.concurrent.CopyOnWriteArrayList<E>

public class CopyOnWriteArrayList<E> implements java.util.List<E>, java.util.RandomAccess, Cloneable, ...