In this chapter we have looked at the basic characteristics of Java, and how portability between different computers is achieved. We have also introduced the elements of object-oriented programming. There are bound to be some aspects of what we have discussed that you don't feel are completely clear to you. Don't worry about it. Everything we have discussed here we will be revisiting again in more detail later on in the book.
The essential points we have covered in this chapter are:
Java applets are programs that are designed to be embedded in an HTML document. Java applications are standalone programs. Java applications can be console programs that only support text output to the screen, or they can be windowed applications with a GUI.
Java programs are intrinsically object-oriented.
Java sourcecode is stored in files with the extension .java.
Java programs are compiled to byte codes, which are instructions for the Java Virtual Machine. The Java Virtual Machine is the same on all the computers on which it is implemented, thus ensuring the portability of Java programs.
Java object code is stored in files with the extension .class.
Java programs are executed by the Java interpreter, which analyses the byte codes and carries out the operations they specify.
The Java System Development Kit ( the SDK) supports the compilation and execution of Java applications and applets.
Experience is what you get when you are expecting something else.