CombinedCollection (Tensegrity API)

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com.tensegrity.generic.util
Class CombinedCollection

java.lang.Object
  com.tensegrity.generic.util.CombinedCollection

All Implemented Interfaces:: java.util.Collection, java.util.List

public class CombinedCollection
extends java.lang.Object
implements java.util.List

Class CombinedCollection merges two collections into a new collection view consisting of the contents of both. Because the underlying collections are not physically combined, the cost of creating the combined List is linear.

An instance does not allow modification to any of its contents, but changes to the underlying collections are immediately reflected. The sole exception is during an iteration. In other words, it is possible to iterate over a CombinedCollection and change the underlying lists without having a ConcurrentModificationException being thrown.

It is not possible to alter the combined collection instance or their contents directly, however.

Unsupported operations will cause a RuntimeException to be thrown, which indicates that the user is trying something defined by the Collection interface yet which contradicts the semantics of the read-only view that a CombinedCollection provides.

The cost of creating a new CombinedCollection instance is very low and allows quick pseudo-concatenation of two existing Collection instances. The resulting object can be traversed with an Iterator and its size can also be determined. Additionally, the instance can be passed to constructors of other standard Collection objects, since its toObject method has been appropriately overridden. The number of operations that are supported by this class are limited, however, and restricted to read-only operations.

Combined collections can be recursively nested. Suppose you have three rather large collections, for example ArrayLists, and you wish to combine them into a single Collection object. The code would look like this:

 public Collection combineArrayLists (ArrayList a, ArrayList b, ArrayList c)
 {
   return new CombinedCollection ( a, new CombinedCollection (b, c));
 }

Version:: $Id: CombinedCollection.java,v 1.29 2005/11/14 15:50:04 KevinCVS Exp $
Author:: StepanRutz

Field Summary
`protected java.util.Collection`	`a` Reference to the first of the two combined collections.
`protected java.util.Collection`	`b` Reference to the second of the two combined collections.

Constructor Summary
`CombinedCollection(java.util.Collection a, java.util.Collection b)` Constructs a new CombinedCollection instance that consists of the two specified

Method Summary
`void`	`add(int index, java.lang.Object element)`
`boolean`	`add(java.lang.Object o)`
`boolean`	`addAll(java.util.Collection c)`
`boolean`	`addAll(int index, java.util.Collection c)`
`void`	`clear()`
`boolean`	`contains(java.lang.Object o)`
`boolean`	`containsAll(java.util.Collection c)`
`java.lang.Object`	`get(int index)`
`int`	`indexOf(java.lang.Object o)`
`boolean`	`isEmpty()`
`java.util.Iterator`	`iterator()`
`int`	`lastIndexOf(java.lang.Object o)`
`java.util.ListIterator`	`listIterator()`
`java.util.ListIterator`	`listIterator(int index)`
`java.lang.Object`	`remove(int index)`
`boolean`	`remove(java.lang.Object o)`
`boolean`	`removeAll(java.util.Collection c)`
`boolean`	`retainAll(java.util.Collection c)`
`java.lang.Object`	`set(int index, java.lang.Object element)`
`int`	`size()`
`java.util.List`	`subList(int fromIndex, int toIndex)`
`java.lang.Object[]`	`toArray()`
`java.lang.Object[]`	`toArray(java.lang.Object[] array)`

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.List

equals, hashCode

Field Detail

a

protected java.util.Collection a

Reference to the first of the two combined collections.

b

protected java.util.Collection b

Reference to the second of the two combined collections.

Constructor Detail