Java™ How to Program, Seventh Edition

18.7. Raw Types

The test programs for generic class Stack in Section 18.6 instantiate Stacks with type arguments Double and Integer. It is also possible to instantiate generic class Stack without specifying a type argument, as follows:

Stack objectStack = new Stack( 5 ); // no type argument specified

In this case, the objectStack is said to have a raw type, which means that the compiler implicitly uses type Object throughout the generic class for each type argument. Thus the preceding statement creates a Stack that can store objects of any type. This is important for backward compatibility with prior versions of Java. For example, the data structures of the Java Collections Framework (see Chapter 19, Collections) all stored references to