org.mortbay.util
Class LazyList

java.lang.Object
  |
  +--java.util.AbstractCollection
        |
        +--java.util.AbstractList
              |
              +--org.mortbay.util.LazyList
All Implemented Interfaces:
java.util.Collection, java.util.List

public class LazyList
extends java.util.AbstractList

Lazy List creation. A List helper class that attempts to avoid unneccessary List creation. If a method needs to create a List to return, but it is expected that this will either be empty or frequently contain a single item, then using LazyList will avoid additional object creations by using Collections.EMPTY_LIST or Collections.singletonList where possible.

Usage

   LazyList lazylist =null;
   while(loopCondition)
   {
     Object item = getItem();
     if (item.isToBeAdded())
         lazylist = LazyList.add(lazylist,item);
   }
   return LazyList.getList(lazylist);
 
An ArrayList of default size is used as the initial LazyList.

Version:
$Revision: 1.3 $
Author:
Greg Wilkins (gregw)
See Also:
List

Method Summary
static LazyList add(LazyList list, int initialSize, java.lang.Object item)
          Add an item to a LazyList
static LazyList add(LazyList list, java.lang.Object item)
          Add an item to a LazyList
 java.lang.Object get(int i)
           
static java.lang.Object get(LazyList list, int i)
          Get item from the list
static java.util.List getList(LazyList list)
          Get the real List from a LazyList.
static java.util.List getList(LazyList list, boolean nullForEmpty)
          Get the real List from a LazyList.
 java.util.Iterator iterator()
           
 java.util.ListIterator listIterator()
           
 java.util.ListIterator listIterator(int i)
           
 int size()
           
static int size(LazyList list)
          The size of a lazy List
 
Methods inherited from class java.util.AbstractList
add, add, addAll, clear, equals, hashCode, indexOf, lastIndexOf, remove, set, subList
 
Methods inherited from class java.util.AbstractCollection
addAll, contains, containsAll, isEmpty, remove, removeAll, retainAll, toArray, toArray, toString
 
Methods inherited from class java.lang.Object
getClass, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface java.util.List
addAll, contains, containsAll, isEmpty, remove, removeAll, retainAll, toArray, toArray
 

Method Detail

add

public static LazyList add(LazyList list,
                           java.lang.Object item)
Add an item to a LazyList
Parameters:
list - The list to add to or null if none yet created.
item - The item to add.
Returns:
The lazylist created or added to.

add

public static LazyList add(LazyList list,
                           int initialSize,
                           java.lang.Object item)
Add an item to a LazyList
Parameters:
list - The list to add to or null if none yet created.
initialSize - A size to use when creating the real list
item - The item to add.
Returns:
The lazylist created or added to.

getList

public static java.util.List getList(LazyList list)
Get the real List from a LazyList.
Parameters:
list - A LazyList returned from LazyList.add(Object)
Returns:
The List of added items, which may be an EMPTY_LIST or a SingletonList.

getList

public static java.util.List getList(LazyList list,
                                     boolean nullForEmpty)
Get the real List from a LazyList.
Parameters:
list - A LazyList returned from LazyList.add(Object) or null
nullForEmpty - If true, null is returned instead of an empty list.
Returns:
The List of added items, which may be null, an EMPTY_LIST or a SingletonList.

size

public static int size(LazyList list)
The size of a lazy List
Parameters:
list - A LazyList returned from LazyList.add(Object) or null
Returns:
the size of the list.

get

public static java.lang.Object get(LazyList list,
                                   int i)
Get item from the list
Parameters:
list - A LazyList returned from LazyList.add(Object) or null
int - i index
Returns:
the item from the list.

get

public java.lang.Object get(int i)
Overrides:
get in class java.util.AbstractList

size

public int size()
Overrides:
size in class java.util.AbstractCollection

listIterator

public java.util.ListIterator listIterator()
Overrides:
listIterator in class java.util.AbstractList

listIterator

public java.util.ListIterator listIterator(int i)
Overrides:
listIterator in class java.util.AbstractList

iterator

public java.util.Iterator iterator()
Overrides:
iterator in class java.util.AbstractList


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