ListE


List<E> java.util

Java 1.2 collection

This interface represents an ordered collection of objects. In Java 5.0 List is a generic interface and the type variable E represents the type of the objects in the list. Each element in a List has an index, or position, in the list, and elements can be inserted, queried, and removed by index. The first element of a List has an index of . The last element in a list has index size ( )-1 .

In addition to the methods defined by the superinterface, Collection , List defines a number of methods for working with its indexed elements. get( ) and set( ) query and set the object at a particular index, respectively. Versions of add( ) and addAll( ) that take an index argument insert an object or Collection of objects at a specified index. The versions of add( ) and addAll( ) that do not take an index argument insert an object or collection of objects at the end of the list. List defines a version of remove( ) that removes the object at a specified index.

The iterator( ) method is just like the iterator( ) method of Collection , except that the Iterator it returns is guaranteed to enumerate the elements of the List in order. listIterator( ) returns a ListIterator object, which is more powerful than a regular Iterator and allows the list to be modified while iteration proceeds. listIterator( ) can take an index argument to specify where in the list iteration should begin.

indexOf( ) and lastIndexOf( ) perform linear searches from the beginning and end, respectively, of the list, searching for a specified object. Each method returns the index of the first matching object it finds, or -1 if it does not find a match. Finally, subList( ) returns a List that contains only a specified contiguous range of list elements. The returned list is simply a view into the original list, so changes in the original List are visible in the returned List . This subList( ) method is particularly useful if you want to sort , search, clear( ) , or otherwise manipulate only a partial range of a larger list.

An interface cannot specify constructors, but it is conventional that all implementations of List provide at least two standard constructors: one that takes no arguments and creates an empty list, and a copy constructor that accepts an arbitrary Collection object that specifies the initial contents of the new List .

As with Collection , List methods that change the contents of the list are optional, and implementations that do not support them simply throw java.lang.UnsupportedOperationException . Different implementations of List may have significantly different efficiency characteristics. For example, the get( ) and set( ) methods of an ArrayList are much more efficient than those of a LinkedList . On the other hand, the add( ) and remove( ) methods of a LinkedList can be more efficient than those of an ArrayList . See also Collection , Set , Map , ArrayList , and LinkedList .

Figure 16-39. java.util.List<E>

 public interface  List<E>  extends Collection<E> {  // Public Instance Methods  boolean  add  (E  o  );        void  add  (int  index  , E  element  );        boolean  addAll  (Collection<? extends E>  c  );        boolean  addAll  (int  index  , Collection<? extends E>  c  );        void  clear  ( );        boolean  contains  (Object  o  );        boolean  containsAll  (Collection<?>  c  );        boolean  equals  (Object  o  );        E  get  (int  index  );        int  hashCode  ( );        int  indexOf  (Object  o  );        boolean  isEmpty  ( );        Iterator<E>  iterator  ( );        int  lastIndexOf  (Object  o  );        ListIterator<E>  listIterator  ( );        ListIterator<E>  listIterator  (int  index  );        boolean  remove  (Object  o  );        E  remove  (int  index  );        boolean  removeAll  (Collection<?>  c  );        boolean  retainAll  (Collection<?>  c  );        E  set  (int  index  , E  element  );        int  size  ( );        List<E>  subList  (int  fromIndex  , int  toIndex  );        Object[ ]  toArray  ( );        <T> T[ ]  toArray  (T[ ]  a  );   } 

Implementations

AbstractList , ArrayList , LinkedList , Vector , java.util.concurrent.CopyOnWriteArrayList

Passed To

Too many methods to list.

Returned By

Too many methods to list.

Type Of

Collections.EMPTY_LIST



Java In A Nutshell
Java In A Nutshell, 5th Edition
ISBN: 0596007736
EAN: 2147483647
Year: 2004
Pages: 1220

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