The Java Developers Almanac 1.4


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e346. Storing Primitive Types in a Collection

Collections can only store objects, not primitive types like int and double. Primitive types must be placed in a wrapper object before they can be placed in a collection. This example demonstrates the storing of int values in a Map.

See also: e58 Wrapping a Primitive Type in a Wrapper Object.

    // Create map
    Map map = new HashMap();
    
    // Create int wrapper object
    Integer refInt = new Integer(123);
    
    // Store int in map
    map.put("key", refInt);
    
    // Get int value from map
    refInt = (Integer)map.get("key");
    
    // Get the integer value from wrapper object
    int i = refInt.intValue();

 Related Examples
e342. Implementing a Queue
e343. Implementing a Stack
e344. Implementing a Least-Recently-Used (LRU) Cache
e345. Listing the Elements of a Collection
e347. Creating a Copy of a Collection
e348. Making a Collection Read-Only

See also: Arrays    Bits    Dates    Hash Tables    Lists    Property Files    Sets    Sorted Collections    Time    Timers   


© 2002 Addison-Wesley.