Summary: Simon continues his exploration of the Java language... with sample code.

Into Java, Part II - Online Manual

By: Simon Gronlund

The Java environment is chock-full of different classes, methods and possibilities. How to get to know it all? Don't do as I did, my first Java lab work. Last year we were using C in our lab works, so I were used of doing quite a lot of work of my own. If I wished a certain object, I had to implement it myself since not so many classes were predefined.

Now our first lab work was to do a text mode application, holding different objects, like rectangles, squares, polygons, circles and so on. Eagerly I jumped straight into the coding part, the planning and designing phase was quickly rushed through. I think it must have been the transport of joy sipping Java, not decaffeinated. So, I did the tiresome work of implementing things, like an abstract RectangleLike class to inherit from (a very important topic of the next column). Finally it was done.

When I then found out that Rectangle is a Java class already implemented, I didn't laugh too much, I'll say! To my relief I soon found out that I wasn't the only one doing that mistake. But stupidity is only allowed once, isn't it?

Javadoc

Please navigate to your Java11 folder. There, find the docs folder, then the api folder. Perhaps you have installed Java 1.1.7 on the C disk, so the path will be C:\Java11\docs\api. Now open the packages.html. For most purposes this is a good starting point, so bookmark it in your browser.

I am not one hundred percent pleased with this IBM documentation. Everything is there, up to 1.1.7, but try for example to load the "index" page. It is a file called AllNames.html, and it's 1,430 kilobyte big. Yes, you were correct, 1.43 MB, and in spite of being on your HD it is still slow to load every now and then. IBM, please make this index file in smaller chunks.

Soon you'll see for yourself why I grunt about this part, but I will explain my feelings right away. Often you have a feeling of what method name to expect, but you would like to check it out. Let's imagine, we are looking for a method that will draw a filled rectangle on the screen. Possibly the method name will be drawRectangle, but we aren't sure, and we don't find this method in the class Rectangle. We will try using the Index. There we click the "D", scrolls and there we are.

After many seconds we have found that the drawing method resides in java.awt.Graphics, that is the class Graphics. But it wasn't drawRectangle we were looking for, since it only draws the outline. A shortcut now is to click the "drawRectangle" and hope that the expected method will reside nearby. Yes! Within the Graphic class, the method above is the one, "fillRect". Consider doing this kind of search a dozen times an hour, with tens of seconds running away waiting for the browser to work every link we use, soon you will get rather tired.

SUN

How to use it?

Mainly the documentation is divided in three categories; the packages, the classes and the methods within a selected class. The Java11/docs/api/API_users_guide.html will give you the basic introduction. I suggest you turn to that page soon and study it.

To sum it up, most time we are going to develop Java app's, we will have a browser open at the same time. I often find myself switching between the code editor and the browser quite a lot. Many times I know what I would like to do, and I know how to do it. I still search the API to see if there is a better way to do it, another method or perhaps to get some other angles of approach.

Of course there are a lot more to know than is written in the API, which for a beginner is too poor. Therefore, never miss an issue of OS/2 e-Zine!