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();

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