In this Ant tutorial installment, we will use ant Properties to specify the work directory structure that will contain our .class and .jar files. The work directory structure tends to be a personal preference, and properties will allow us to centralize the structure definition so that any change will be relatively pain-free. We specify the directories with a location attribute, thereby binding the property to a file system location. This allows us to pass the property to another ant process without any local directory side effects.

The deeper you delve into the innards of a particular technology, the better you'll understand it. Computer technologies are like the open expanse of the Sea; it all looks the same on the surface, but when you dive below into the deep, you discover wonders you'd never have dreamt existed. The Java programming language has no pointers, so it's very difficult for programmers to find out what's happening under the hood. The .class file comes tumbling across the wires and executes on you machine, but it's difficult to figure out how. An in-depth discussion of the .class file will help clear up a lot of your doubts. For example, in C/C++ when we use printf(), we know that the linker adds the code for that function into our .exe file, but that's not what happens when we say System.out.println in Java. You can only discover the details by reading the .class file.

You carefully designed your code, got it to compile, and now it does not work correctly. What should you do? The first method most people use is to add a lot of print statements. This method requires recompiling your code and often takes many tries to see what you want. Using a debugger is a much more efficient method of doing this work. Debuggers allow one, among other things, to examine variables, change the values, and control the execution of the program.Keep in mind that a debugger isn't a substitute for thinking. It is important to reason through how things may have happened and to choose the test data intelligently.

DDD is a graphical interface that allows debugging of many different types of code. It supports C++, JAVA, perl, and other choices. There are several advantages to DDD. First, once you learn it for one language you can use the same techniques on other languages. Second, its graphical interface is much easier to use then most of the other Unix debuggers. This will make your life easier (and it will be more like the PC if you are used to that!).

First things first. This chapter will show you the structure of an applet, the basic drawing methods, how to use images and how to create a user interface.
It really is not that hard, and you will be able to perform visual actions within a few minutes