Inner classes and implementation of ArrayList - Data Structures and Problem Solving Using Java - page 581

1 package weiss.util;
2
3 /**
4 * AbstractCollection provides default implementations for
5 * some of the easy methods in the Collection interface.
6 */
7 public abstract class AbstractCollection<AnyType> implements Collection<AnyType>
8 {
9 /**
10 * Tests if this collection is empty.
11 * @return true if the size of this collection is zero.
12 */
13 public boolean isEmpty( )
14 {
15 return size( ) == 0;
16 }
17
18 /**
19 * Change the size of this collection to zero.
20 */
21 public void clear( )
22 {
23 Iterator<AnyType> itr = iterator( );
24 while( itr.hasNext( ) )
25 {
26 itr.next( );
27 itr.remove( );
28 }
29 }
30
31 /**
32 * Adds x to this collections.
33 * This default implementation always throws an exception.
34 * @param x the item to add.
35 * @throws UnsupportedOperationException always.
36 */
37 public boolean add( AnyType x )
38 {
39 throw new UnsupportedOperationException( );
40 }
figure 15.10
Sample implementation of AbstractCollection (part 1)
of contains and remove . Both implementations use a sequential search, so they
are not efficient, and need to be overridden by respectable implementations of
the Set interface.