Package com.tangosol.util

Class CircularArrayList

java.lang.Object
java.util.AbstractCollection
java.util.AbstractList
com.tangosol.util.CircularArrayList
All Implemented Interfaces:
Serializable, Cloneable, Iterable, Collection, List, RandomAccess, SequencedCollection
public class CircularArrayList extends AbstractList implements List, RandomAccess, Cloneable, Serializable
Resizable-array implementation of the List interface. Implements all optional list operations, and permits all elements, including null. (This class is roughly equivalent to ArrayList, except that it is optimized for removing elements at the front and back of the list to facilitate use as a queue or deque.

The size, isEmpty, get, set, iterator, and listIterator operations run in constant time. The add operation runs in amortized constant time, that is, adding n elements requires O(n) time. All of the other operations run in linear time (roughly speaking). The constant factor is low compared to that for the LinkedList implementation.

Each CircularArrayList instance has a capacity. The capacity is the size of the array used to store the elements in the list. It is always at least as large as the list size. As elements are added to an CircularArrayList, its capacity grows automatically. The details of the growth policy are not specified beyond the fact that adding an element has constant amortized time cost.

An application can increase the capacity of an CircularArrayList instance before adding a large number of elements using the ensureCapacity operation. This may reduce the amount of incremental reallocation.

Note that this implementation is not synchronized. If multiple threads access a CircularArrayList concurrently, and at least one of the threads modifies the list structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more elements, or explicitly resizes the backing array; merely setting the value of an element is not a structural modification.) This is typically accomplished by synchronizing on some object that naturally encapsulates the list. If no object exists, the list should be "wrapped" using the Collections.synchronizedList method. This is best done at creation time, to prevent accidental unsynchronized access to the list: 

   List list = Collections.synchronizedList(new CircularArrayList(...));

The iterators returned by this class's iterator and listIterator methods are fail-fast: if list is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, the iterator will throw a ConcurrentModificationException. Thus, in the face of concurrent modification, the iterator fails quickly and cleanly, rather than risking arbitrary, non-deterministic behavior at an undetermined time in the future.

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis. Therefore, it would be wrong to write a program that depended on this exception for its correctness: the fail-fast behavior of iterators should be used only to detect bugs.

Since:
Coherence 3.5
Author:
djl 2008.10.22
See Also:

  • Field Details

    • m_aoData

      protected Object[] m_aoData
      The array into which the elements of the list are stored. The capacity of the list is the length of this array buffer.

    • m_iFirst

      protected int m_iFirst
      The offset to the first element.

    • m_iLast

      protected int m_iLast
      The offset to one past the last element.

    • m_cElements

      protected int m_cElements
      The size of the list (the number of elements it contains).

  • Constructor Details

    • CircularArrayList

      public CircularArrayList()
      Create a new CircularArrayList with default settings.

    • CircularArrayList

      public CircularArrayList(int cInitialElements)
      Create a new CircularArrayList with the specified initial capacity.
      Parameters:
      cInitialElements - the initial capacity of the list
      Throws:
      IllegalArgumentException - if the specified initial capacity is negative

    • CircularArrayList

      public CircularArrayList(Collection c)
      Construct a CircularArrayList containing the elements of the specified collection in the order they are returned by the collection's iterator.
      Parameters:
      c - the collection whose elements are to be placed into this list

  • Method Details

    • trimToSize

      public void trimToSize()
      Trim the capacity of this list instance to be as small as possible.

    • ensureCapacity

      public boolean ensureCapacity(int cMin)
      Increase the capacity of this list instance, if necessary, to ensure that it can hold at least the specified number of elements.
      Parameters:
      cMin - the minimum allowable capacity
      Returns:
      true if the capacity was increased

    • size

      public int size()
      Specified by:
      size in interface Collection
      Specified by:
      size in interface List
      Specified by:
      size in class AbstractCollection

    • isEmpty

      public boolean isEmpty()
      Specified by:
      isEmpty in interface Collection
      Specified by:
      isEmpty in interface List
      Overrides:
      isEmpty in class AbstractCollection

    • contains

      public boolean contains(Object o)
      Specified by:
      contains in interface Collection
      Specified by:
      contains in interface List
      Overrides:
      contains in class AbstractCollection

    • indexOf

      public int indexOf(Object o)
      Search for the first occurence of the given argument, testing for equality using the equals method.
      Specified by:
      indexOf in interface List
      Overrides:
      indexOf in class AbstractList
      Parameters:
      o - the element to search for
      Returns:
      the index of the first occurrence of the argument in this list; returns -1 if the object is not found

    • lastIndexOf

      public int lastIndexOf(Object o)
      Returns the index of the last occurrence of the specified object in this CycicArrayList.
      Specified by:
      lastIndexOf in interface List
      Overrides:
      lastIndexOf in class AbstractList
      Parameters:
      o - the element to search for
      Returns:
      the index of the last occurrence of the specified object in this list; returns -1 if the object is not found

    • toArray

      public Object[] toArray()
      Specified by:
      toArray in interface Collection
      Specified by:
      toArray in interface List
      Overrides:
      toArray in class AbstractCollection

    • toArray

      public Object[] toArray(Object[] ao)
      Specified by:
      toArray in interface Collection
      Specified by:
      toArray in interface List
      Overrides:
      toArray in class AbstractCollection

    • get

      public Object get(int index)
      Specified by:
      get in interface List
      Specified by:
      get in class AbstractList

    • set

      public Object set(int index, Object o)
      Specified by:
      set in interface List
      Overrides:
      set in class AbstractList

    • add

      public boolean add(Object o)
      Specified by:
      add in interface Collection
      Specified by:
      add in interface List
      Overrides:
      add in class AbstractList

    • add

      public void add(int index, Object o)
      Insert the element at the specified position in this list. Shifts the element currently at that position (if any) and any subsequent elements to the right (adds one to their indices).
      Specified by:
      add in interface List
      Overrides:
      add in class AbstractList
      Parameters:
      index - the index at which the specified element will be inserted
      o - the element to be inserted
      Throws:
      IndexOutOfBoundsException - if index is out of range

    • remove

      public Object remove(int index)
      Removes the element at the specified position in this list. Shifts any subsequent elements to the left (subtracts one from their indices).
      Specified by:
      remove in interface List
      Overrides:
      remove in class AbstractList
      Parameters:
      index - the index of the element to removed
      Returns:
      the element that was removed from the list
      Throws:
      IndexOutOfBoundsException - if index out of range

    • clear

      public void clear()
      Specified by:
      clear in interface Collection
      Specified by:
      clear in interface List
      Overrides:
      clear in class AbstractList

    • addAll

      public boolean addAll(Collection c)
      Appends all of the elements in the specified Collection to the end of this list, in the order that they are returned by the specified Collection's Iterator. The behavior of this operation is undefined if the specified Collection is modified while the operation is in progress. (This implies that the behavior of this call is undefined if the specified Collection is this list, and this list is nonempty.)
      Specified by:
      addAll in interface Collection
      Specified by:
      addAll in interface List
      Overrides:
      addAll in class AbstractCollection
      Parameters:
      c - the elements to be inserted into this list
      Returns:
      true if this list changed as a result of the call
      Throws:
      NullPointerException - if the specified collection is null.

    • addAll

      public boolean addAll(int index, Collection c)
      Inserts all of the elements in the specified Collection into this list, starting at the specified position. Shift the element currently at that position (if any) and any subsequent elements to the right (increases their indices). The new elements will appear in the list in the order that they are returned by the specified Collection's iterator.
      Specified by:
      addAll in interface List
      Overrides:
      addAll in class AbstractList
      Parameters:
      index - the index at which to insert first element from the specified collection
      c - the elements to be inserted into this list
      Returns:
      true if this list changed as a result of the call
      Throws:
      IndexOutOfBoundsException - if index out of range
      NullPointerException - if the specified Collection is null

    • removeRange

      protected void removeRange(int fromIndex, int toIndex)
      Removes from this list all of the elements whose indexes are between fromIndex, inclusive and toIndex, exclusive. Shifts any succeeding elements to the left (reduces their index). This call shortens the list by (toIndex - fromIndex) elements. (If toIndex==fromIndex, this operation has no effect.)
      Overrides:
      removeRange in class AbstractList
      Parameters:
      fromIndex - the index of first element to be removed
      toIndex - the index after last element to be removed.

    • clone

      public Object clone()
      Returns a shallow copy of this list instance. The elements themselves are not copied.
      Overrides:
      clone in class Object
      Returns:
      a clone of this list instance

    • effectiveIndex

      protected int effectiveIndex(int index)
      Calculate the effective index taking into account offsets and the circular nature of CircularArrayList.
      Parameters:
      index - the index to transform
      Returns:
      the effective index in the physical storage array

    • rangeCheck

      protected void rangeCheck(int index)
      Check if the given index is in range. If not, throw an appropriate runtime exception.
      Parameters:
      index - the index to be checked for being between size() and 0 inclusive
      Throws:
      IndexOutOfBoundsException - if the index is not in the range

    • ensureEffectiveIndex

      protected int ensureEffectiveIndex(int index)
      After range checking Calculate the effective index while taking into account the offsets and the circular nature of the list.
      Parameters:
      index - the index to transform
      Returns:
      the effective index in the physical storage array
      Throws:
      IndexOutOfBoundsException - if the index is not in the range

    • ensureCompactness

      protected boolean ensureCompactness()
      Ensure the representation of this list is appropriatly compact by shrinking if necessary.
      Returns:
      true if an actual compaction happened; false otherwise

    • dump

      public void dump()
      Outputs information to standard output about representation for debugging purposes.