In this chapter you've looked at the basic characteristics of Java, and how portability between different computers is achieved. I have also introduced you to the elements of object-oriented programming. There are bound to be some aspects of what I've discussed that you don't feel are completely clear to you. Don't worry about it. Everything I have discussed here I will be revisiting again in more detail later on in the book.
The essential points I 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 source code is stored in files with the extension .java.
Java programs are compiled to bytecodes, 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 bytecodes and carries out the operations they specify.
The Java Development Kit (JDK) supports the compilation and execution of Java applications and applets.