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Practise Typing & Typed By Stephen Chung From  [ 訪客無法瀏覽此圖片或下載點，請先註冊或登入會員。]

Getting Started

THIS chapter gives a quick introduction to the Java technology. First, we explain what the Java platform is and what it can do. Next are step-by-step instructions on how to compile and run two simple programs on the Win32, the UNIX/Linux or the MacOS platforms. After that, we take a look at the code for the two programs, so you can see how they work. The chapter ends with questions and exercises to test and expand your knowledge, followed by a table of download instructions for the code used in this chapter.

The software development knits (SDKs) that Sun Microsystems provides include a minimal set of tools to let you run and compile your programs. Serious developers are advised to use a professional Integrated Development Environment (IDE). See Integrated Development Environments (page 540) for a list of IDEs.

About the Java Technology

Talk about Java technology seems to be everywhere, but what exactly is it? The next two sections explain how it is both a programming language and a platform.

The Java Programming Language

The Java programming language is a high-level language that can be characterized by all the following buzzwords:

When you’re finished, the dialog box should look like Figure 5. Now click Save and exit NotePad.

Compile the Souce File
From the Start menu, select the MS-DOS Prompt (Windows 95/98) or Command Prompt (Windows NT/2000) application. When the application launches, it should look like Figure 6.

The prompt shows your current directory. When you bring up the prompt for Windows 95/98, your current directory is usually WINDOWS on your C drive (as shown in Figure 6) or WINNT for Windows NT. To compile your source code file, changes your current directory to the one in which your file is located. For example, if your source directory is java on the C drive, you would type the following command at the prompt and press Enter:
cd c:\java

Now the prompt should change to C;\java. To change to a directory on a different drive, you must type an extra command. As shown in Figure 7, to change to the java directory on the D drive, you must reenter the drive, d:.

In our example, the java directory is on the C drive. The dir command lists the files in your current directory. If your current directory is C:\java and your enter dir at the prompt, you should see your file (Figure 8).

Now You can compile. At the prompt, type the following command and press Enter:
        Javac HelloWorldApp.java
If your prompt reappears without error messages, congratulations. You have successfully compiles your program. If you encounter errors, see Error Explanation (Win32) to help you fix the problems.

The compiler has generated a Java bytecode file, HelloWorldApp.class. At the prompt, type dir to see the new file that was generated (Figure 9). Now that you have a .class file, you can run your program.

Run the program
In the same directory, enter the following command at prompt:
        Java HelloWorldApp

Figure 10 shows what you should see.

Creating Your First Applet
HelloWorldApp is an example of an application, a standalone program. Now you will create an applet called HelloWorld,  [color=blue][size=2][ [u]瀏覽完整內容請先註冊或登入會員[/u]。][/size][/color]