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Compiling the Program into a Class File
Before you can try out the program, it must be compiled. The term compile might be unfamiliar to you now, but you will become quite familiar with it in the coming hours. When you compile a program, you take the instructions you have given the computer and convert them into a form the computer can better understand. You also make the program run as efficiently as possible. Java programs must be compiled before you can run them. With the Java Development Kit, programs are compiled using the javac program.
The javac program, like all programs included with the Kit, is a command-line utility. You run the program by using your keyboard to type a command at a command line that can accept the input.
Because most Linux usage is handled at the command line, readers with that operating system will be familiar with how the Kit's programs are used. Anyone who used MS-DOS prior to the introduction of Windows also has used a command line.
Many Windows users might not be aware that their operating system includes a command-line feature of its own: the MS-DOS Command Prompt window.
To get to a command line in Windows:
On a Mac, access a command line by choosing Applications, Utilities, Terminal. To compile the Saluton program using the Java Development Kit, go to a command line, open the folder on your system where the Saluton.java file is located, then type the following at the command line:
If the program compiles successfully, a new file called Saluton.class is created in the same folder as Saluton.java. If you see any error messages, refer to the following section, "Fixing Errors." All Java programs are compiled into class files which are given the .class file extension. A Java program can be made up of several classes that work together, but in a simple program such as Saluton only one class is needed.
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