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Thinking in Java
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Summary

To review the containers provided in the standard Java library:

  1. An array associates numerical indices to objects. It holds objects of a known type so that you don’t have to cast the result when you’re looking up an object. It can be multidimensional, and it can hold primitives. However, its size cannot be changed once you create it.
  2. A Collection holds single elements, and a Map holds associated pairs.
  3. Like an array, a List also associates numerical indices to objects—you can think of arrays and Lists as ordered containers. The List automatically resizes itself as you add more elements. But a List can hold only Object references, so it won’t hold primitives, and you must always cast the result when you pull an Object reference out of a container.
  4. Use an ArrayList if you’re doing a lot of random accesses, but a LinkedList if you will be doing a lot of insertions and removals in the middle of the list.
  5. The behavior of queues, deques, and stacks is provided via the LinkedList.
  6. A Map is a way to associate not numbers, but objects with other objects. The design of a HashMap is focused on rapid access, whereas a TreeMap keeps its keys in sorted order, and thus is not as fast as a HashMap. A LinkedHashMap keeps its elements in insertion order, but may also reorder them with its LRU algorithm.
  7. A Set only accepts one of each type of object. HashSets provide maximally fast lookups, whereas TreeSets keep the elements in sorted order. LinkedHashSets keep elements in insertion order. There’s no need to use the legacy classes Vector, Hashtable, and Stack in new code.
    Thinking in Java
    Prev Contents / Index Next

 
 
   Reproduced courtesy of Bruce Eckel, MindView, Inc. Design by Interspire