Summary

We have barely scratched the surface, both in terms of Java as well as OO

Java

• Not covered:– C.21: applets– C.22: network programming ( 312 next year)

• Java 2:– Improved Collection class stuff– Swing in addition to AWT– Better graphics: Java2D, Java3D– Internationalization– Java beans– JNI: java native interface– Sound– JDBC: connect to SQL databases– RMI: remote method invocation– Servlets

Java development• Java 1.3:

– Lots of improvement to libraries– (HotSpot)– Reflection– Corba– Applet caching/jar indexing

• Java 1.4:– NIO: New IO API– XML– Better Swing performance– Assertion facility– AWT: full-screen mode, headless support, better focus architecture

• Java 1.5: – Generics (templates)– …

Object-oriented concepts

• Multiple inheritance– Not just interface, but also implementation (=

code)– Need “conflict resolution”

• Inherit same names (fields or methods) along multiple pathes

• C++: user must specify explicitly• Dylan, Common Lisp: automatic, use a class-

precedence list

Prototypes

• No distinction between Class and Instance

• Every instance can be used as the Prototype (“class”) for other instances, use socalled delegation instead of methods

• Usually rather dynamic

• SELF system (was also important milestone for JIT research)

• NewtonOS

Generic functions (Dylan, CL)

• All parameters influence method selection (cf. parametric overloading: 2step process)

• Generic functions: all arguments’ runtime types influence choice (theoretically slower)

• Not directly attached to a single class:defeats(Object a, Object b) { return false;}

defeats(Paper a, Rock b) {return true;}

defeats(Rock a, Scissors b) {return true;}

defeats(Scissors a, Paper b) {return true;}

Predicate dispatch

Predicate dispatch

Multiple dispatch

Single dispatch

Cecil,…

Dylan, CL,…

Java, C++,Smalltalk, Delphi,…

public int f(A x, B y) when x.df1() instanceOf C or not(y instanceOf D) { …}

• Keep (having fun) – learning about Java (and possibly other programming

languages)– practising by writing more and more complex

programs

• How: – 3rd/4th year papers– Books (library)– Internet (WWW, newsgroups, mailing-lists)