public interface

List

implements Collection<E>
java.util.List<E>
Known Indirect Subclasses

Class Overview

A List is a collection which maintains an ordering for its elements. Every element in the List has an index. Each element can thus be accessed by its index, with the first index being zero. Normally, Lists allow duplicate elements, as compared to Sets, where elements have to be unique.

Summary

Public Methods
abstract boolean add(E object)
Adds the specified object at the end of this List.
abstract void add(int location, E object)
Inserts the specified object into this List at the specified location.
abstract boolean addAll(Collection<? extends E> collection)
Adds the objects in the specified collection to the end of this List.
abstract boolean addAll(int location, Collection<? extends E> collection)
Inserts the objects in the specified collection at the specified location in this List.
abstract void clear()
Removes all elements from this List, leaving it empty.
abstract boolean contains(Object object)
Tests whether this List contains the specified object.
abstract boolean containsAll(Collection<?> collection)
Tests whether this List contains all objects contained in the specified collection.
abstract boolean equals(Object object)
Compares the given object with the List, and returns true if they represent the same object using a class specific comparison.
abstract E get(int location)
Returns the element at the specified location in this List.
abstract int hashCode()
Returns the hash code for this List.
abstract int indexOf(Object object)
Searches this List for the specified object and returns the index of the first occurrence.
abstract boolean isEmpty()
Returns whether this List contains no elements.
abstract Iterator<E> iterator()
Returns an iterator on the elements of this List.
abstract int lastIndexOf(Object object)
Searches this List for the specified object and returns the index of the last occurrence.
abstract ListIterator<E> listIterator(int location)
Returns a list iterator on the elements of this List.
abstract ListIterator<E> listIterator()
Returns a List iterator on the elements of this List.
abstract E remove(int location)
Removes the object at the specified location from this List.
abstract boolean remove(Object object)
Removes the first occurrence of the specified object from this List.
abstract boolean removeAll(Collection<?> collection)
Removes all occurrences in this List of each object in the specified collection.
abstract boolean retainAll(Collection<?> collection)
Removes all objects from this List that are not contained in the specified collection.
abstract E set(int location, E object)
Replaces the element at the specified location in this List with the specified object.
abstract int size()
Returns the number of elements in this List.
abstract List<E> subList(int start, int end)
Returns a List of the specified portion of this List from the given start index to the end index minus one.
abstract Object[] toArray()
Returns an array containing all of the elements in this list in proper sequence (from first to last element).
abstract <T> T[] toArray(T[] a)
Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array.
[Expand]
Inherited Methods
From interface java.lang.Iterable
From interface java.util.Collection

Public Methods

public abstract boolean add (E object)

Adds the specified object at the end of this List.

Parameters
object the object to add.
Returns
  • always true.
Throws
UnsupportedOperationException if adding to this List is not supported.
ClassCastException if the class of the object is inappropriate for this List.
IllegalArgumentException if the object cannot be added to this List.

public abstract void add (int location, E object)

Inserts the specified object into this List at the specified location. The object is inserted before the current element at the specified location. If the location is equal to the size of this List, the object is added at the end. If the location is smaller than the size of this List, then all elements beyond the specified location are moved by one position towards the end of the List.

Parameters
location the index at which to insert.
object the object to add.
Throws
UnsupportedOperationException if adding to this List is not supported.
ClassCastException if the class of the object is inappropriate for this List.
IllegalArgumentException if the object cannot be added to this List.
IndexOutOfBoundsException if location < 0 || location > size()

public abstract boolean addAll (Collection<? extends E> collection)

Adds the objects in the specified collection to the end of this List. The objects are added in the order in which they are returned from the collection's iterator.

Parameters
collection the collection of objects.
Returns
  • true if this List is modified, false otherwise (i.e. if the passed collection was empty).
Throws
UnsupportedOperationException if adding to this List is not supported.
ClassCastException if the class of an object is inappropriate for this List.
IllegalArgumentException if an object cannot be added to this List.

public abstract boolean addAll (int location, Collection<? extends E> collection)

Inserts the objects in the specified collection at the specified location in this List. The objects are added in the order they are returned from the collection's iterator.

Parameters
location the index at which to insert.
collection the collection of objects to be inserted.
Returns
  • true if this List has been modified through the insertion, false otherwise (i.e. if the passed collection was empty).
Throws
UnsupportedOperationException if adding to this List is not supported.
ClassCastException if the class of an object is inappropriate for this List.
IllegalArgumentException if an object cannot be added to this List.
IndexOutOfBoundsException if location < 0 || > size()

public abstract void clear ()

Removes all elements from this List, leaving it empty.

Throws
UnsupportedOperationException if removing from this List is not supported.
See Also

public abstract boolean contains (Object object)

Tests whether this List contains the specified object.

Parameters
object the object to search for.
Returns
  • true if object is an element of this List, false otherwise

public abstract boolean containsAll (Collection<?> collection)

Tests whether this List contains all objects contained in the specified collection.

Parameters
collection the collection of objects
Returns
  • true if all objects in the specified collection are elements of this List, false otherwise.

public abstract boolean equals (Object object)

Compares the given object with the List, and returns true if they represent the same object using a class specific comparison. For Lists, this means that they contain the same elements in exactly the same order.

Parameters
object the object to compare with this object.
Returns
  • boolean true if the object is the same as this object, and false if it is different from this object.
See Also

public abstract E get (int location)

Returns the element at the specified location in this List.

Parameters
location the index of the element to return.
Returns
  • the element at the specified location.
Throws
IndexOutOfBoundsException if location < 0 || >= size()

public abstract int hashCode ()

Returns the hash code for this List. It is calculated by taking each element' hashcode and its position in the List into account.

Returns
  • the hash code of the List.

public abstract int indexOf (Object object)

Searches this List for the specified object and returns the index of the first occurrence.

Parameters
object the object to search for.
Returns
  • the index of the first occurrence of the object or -1 if the object was not found.

public abstract boolean isEmpty ()

Returns whether this List contains no elements.

Returns
  • true if this List has no elements, false otherwise.
See Also

public abstract Iterator<E> iterator ()

Returns an iterator on the elements of this List. The elements are iterated in the same order as they occur in the List.

Returns
  • an iterator on the elements of this List.
See Also

public abstract int lastIndexOf (Object object)

Searches this List for the specified object and returns the index of the last occurrence.

Parameters
object the object to search for.
Returns
  • the index of the last occurrence of the object, or -1 if the object was not found.

public abstract ListIterator<E> listIterator (int location)

Returns a list iterator on the elements of this List. The elements are iterated in the same order as they occur in the List. The iteration starts at the specified location.

Parameters
location the index at which to start the iteration.
Returns
  • a list iterator on the elements of this List.
Throws
IndexOutOfBoundsException if location < 0 || location > size()
See Also

public abstract ListIterator<E> listIterator ()

Returns a List iterator on the elements of this List. The elements are iterated in the same order that they occur in the List.

Returns
  • a List iterator on the elements of this List
See Also

public abstract E remove (int location)

Removes the object at the specified location from this List.

Parameters
location the index of the object to remove.
Returns
  • the removed object.
Throws
UnsupportedOperationException if removing from this List is not supported.
IndexOutOfBoundsException if location < 0 || >= size()

public abstract boolean remove (Object object)

Removes the first occurrence of the specified object from this List.

Parameters
object the object to remove.
Returns
  • true if this List was modified by this operation, false otherwise.
Throws
UnsupportedOperationException if removing from this List is not supported.

public abstract boolean removeAll (Collection<?> collection)

Removes all occurrences in this List of each object in the specified collection.

Parameters
collection the collection of objects to remove.
Returns
  • true if this List is modified, false otherwise.
Throws
UnsupportedOperationException if removing from this List is not supported.

public abstract boolean retainAll (Collection<?> collection)

Removes all objects from this List that are not contained in the specified collection.

Parameters
collection the collection of objects to retain.
Returns
  • true if this List is modified, false otherwise.
Throws
UnsupportedOperationException if removing from this List is not supported.

public abstract E set (int location, E object)

Replaces the element at the specified location in this List with the specified object. This operation does not change the size of the List.

Parameters
location the index at which to put the specified object.
object the object to insert.
Returns
  • the previous element at the index.
Throws
UnsupportedOperationException if replacing elements in this List is not supported.
ClassCastException if the class of an object is inappropriate for this List.
IllegalArgumentException if an object cannot be added to this List.
IndexOutOfBoundsException if location < 0 || >= size()

public abstract int size ()

Returns the number of elements in this List.

Returns
  • the number of elements in this List.

public abstract List<E> subList (int start, int end)

Returns a List of the specified portion of this List from the given start index to the end index minus one. The returned List is backed by this List so changes to it are reflected by the other.

Parameters
start the index at which to start the sublist.
end the index one past the end of the sublist.
Returns
  • a list of a portion of this List.
Throws
IndexOutOfBoundsException if start < 0, start > end or end > size()

public abstract Object[] toArray ()

Returns an array containing all of the elements in this list in proper sequence (from first to last element).

The returned array will be "safe" in that no references to it are maintained by this list. (In other words, this method must allocate a new array even if this list is backed by an array). The caller is thus free to modify the returned array.

This method acts as bridge between array-based and collection-based APIs.

Returns
  • an array containing all of the elements in this list in proper sequence
See Also

public abstract T[] toArray (T[] a)

Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array. If the list fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this list.

If the list fits in the specified array with room to spare (i.e., the array has more elements than the list), the element in the array immediately following the end of the list is set to null. (This is useful in determining the length of the list only if the caller knows that the list does not contain any null elements.)

Like the toArray() method, this method acts as bridge between array-based and collection-based APIs. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs.

Suppose x is a list known to contain only strings. The following code can be used to dump the list into a newly allocated array of String: 

 String[] y = x.toArray(new String[0]);
Note that toArray(new Object[0]) is identical in function to toArray().

Parameters
a the array into which the elements of this list are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose.
Returns
  • an array containing the elements of this list
Throws
ArrayStoreException if the runtime type of the specified array is not a supertype of the runtime type of every element in this list
NullPointerException if the specified array is null