org.eclipse.jetty.util

## Class LazyList

- java.lang.Object
- - org.eclipse.jetty.util.LazyList

- All Implemented Interfaces:
    Serializable, Cloneable

      public class LazyList
      extends Object
      implements Cloneable, Serializable

  Lazy List creation. A List helper class that attempts to avoid unnecessary 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(Object)` where possible.

  LazyList works by passing an opaque representation of the list in and out of all the LazyList methods. This opaque object is either null for an empty list, an Object for a list with a single entry or an `ArrayList` for a list of items.

  #### Usage

         Object 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.
  See Also:
    `List`, Serialized Form

- - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `static Object` | `add(Object list, int index, Object item)` Add an item to a LazyList
    `static Object` | `add(Object list, Object item)` Add an item to a LazyList
    `static Object` | `addArray(Object list, Object[] array)` Add the contents of an array to a LazyList
    `static Object` | `addCollection(Object list, Collection<?> collection)` Add the contents of a Collection to a LazyList
    `static <T> T[]` | `addToArray(T[] array, T item, Class<?> type)` Add element to an array
    `static <E> List<E>` | `array2List(E[] array)`
    `static Object` | `clone(Object list)`
    `static boolean` | `contains(Object list, Object item)`
    `static Object` | `ensureSize(Object list, int initialSize)` Ensure the capacity of the underlying list.
    `static <E> E` | `get(Object list, int i)` Get item from the list
    `static <E> List<E>` | `getList(Object list)` Get the real List from a LazyList.
    `static <E> List<E>` | `getList(Object list, boolean nullForEmpty)` Get the real List from a LazyList.
    `static <E> Iterator<E>` | `iterator(Object list)`
    `static <E> ListIterator<E>` | `listIterator(Object list)`
    `static Object` | `remove(Object list, int i)`
    `static Object` | `remove(Object list, Object o)`
    `static <T> T[]` | `removeFromArray(T[] array, Object item)`
    `static int` | `size(Object list)` The size of a lazy List
    `static Object` | `toArray(Object list, Class<?> clazz)` Convert a lazylist to an array
    `static String` | `toString(Object list)`
    `static String[]` | `toStringArray(Object list)`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Method Detail

    - #### add

          public static Object add(Object list,
                   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 Object add(Object list,
                   int index,
                   Object item)

      Add an item to a LazyList
      Parameters:
        `list` - The list to add to or null if none yet created.
        `index` - The index to add the item at.
        `item` - The item to add.
      Returns:
        The lazylist created or added to.

    - #### addCollection

          public static Object addCollection(Object list,
                             Collection<?> collection)

      Add the contents of a Collection to a LazyList
      Parameters:
        `list` - The list to add to or null if none yet created.
        `collection` - The Collection whose contents should be added.
      Returns:
        The lazylist created or added to.

    - #### addArray

          public static Object addArray(Object list,
                        Object[] array)

      Add the contents of an array to a LazyList
      Parameters:
        `list` - The list to add to or null if none yet created.
        `array` - The array whose contents should be added.
      Returns:
        The lazylist created or added to.

    - #### ensureSize

          public static Object ensureSize(Object list,
                          int initialSize)

      Ensure the capacity of the underlying list.

    - #### remove

          public static Object remove(Object list,
                      Object o)

    - #### remove

          public static Object remove(Object list,
                      int i)

    - #### getList

          public static <E> List<E> getList(Object 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 <E> List<E> getList(Object 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.

    - #### toStringArray

          public static String[] toStringArray(Object list)

    - #### toArray

          public static Object toArray(Object list,
                       Class<?> clazz)

      Convert a lazylist to an array
      Parameters:
        `list` - The list to convert
        `clazz` - The class of the array, which may be a primitive type
      Returns:
        array of the lazylist entries passed in

    - #### size

          public static int size(Object 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 <E> E get(Object list,
                  int i)

      Get item from the list
      Parameters:
        `list` - A LazyList returned from LazyList.add(Object) or null
        `i` - int index
      Returns:
        the item from the list.

    - #### contains

          public static boolean contains(Object list,
                         Object item)

    - #### clone

          public static Object clone(Object list)

    - #### toString

          public static String toString(Object list)

    - #### iterator

          public static <E> Iterator<E> iterator(Object list)

    - #### listIterator

          public static <E> ListIterator<E> listIterator(Object list)

    - #### array2List

          public static <E> List<E> array2List(E[] array)

      Parameters:
        `array` - Any array of object
      Returns:
        A new modifiable list initialised with the elements from `array`.

    - #### addToArray

          public static <T> T[] addToArray(T[] array,
                           T item,
                           Class<?> type)

      Add element to an array
      Parameters:
        `array` - The array to add to (or null)
        `item` - The item to add
        `type` - The type of the array (in case of null array)
      Returns:
        new array with contents of array plus item

    - #### removeFromArray

          public static <T> T[] removeFromArray(T[] array,
                                Object item)

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