Basic HTML version of Foils prepared 18 May 97

Foil 43 Java Language -- Types of Classes - II

From Java Tutorial - Spring 1997 Part II: Java Language and Object-Oriented Concepts Peking Tutorial, Web Certificate -- Spring-Summer 1997. by Nancy J. McCracken,Geoffrey C. Fox


1 threadsafe: Instance or static variables will never change asynchronously and so can use compiler optimizations such as assigning to registers. Next modifier -- final -- is also valuable to compilers
2 final -- Cannot have a subclass for classes
  • cannot be overridden for methods
  • final variables have a constant value e.g.
    • final int ageatdeath = 101;
3 transient -- specifies that objects are not persistent
4 Note most of these modifiers can be used either for a class or an object -- a particular instance of a class
  • abstract only makes sense for a class and transient is perhaps more useful on an object basis

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