Basic HTML version of Foils prepared 16 May 98

Foil 55 Java Features -- It's Dynamic

From Introduction to Java to be used in (Scientific) Computing CEWES Java Tutorial -- Spring Semester 98. by Geoffrey C. Fox, Nancy McCracken


1 Java model is more dynamic than C++ and closer to Smalltalk or Perl.
2 Subclasses don't need to to be recompiled after superclass implementation is updated.
3 C++ has "fragile superclass" problem where must recompile children if change anything (method/instance variable) in a superclass or referenced class -- Java resolves references at runtime and avoids this.
4 Classes have runtime representation (implemented in terms of the Class class) which allows one to look up type of a given object instance at runtime (in C cannot know if pointer is to integer or browser!)
  • JDK1.1 allows introspection to dynamically find out the structure of a class at runtime
  • used for automatic object serialization as when sending over network or saving on disk

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