Java Notes

Compiling a Java program

Turning a Java source program into an object program takes a couple of steps. Assuming that you are using the popular, but awkward, JDK (Java Development Kit) by Sun Microsystems, do the following:
  1. Create the source program with a text editor (eg, jEdit, TextPad, ...). Save it in a file with the same name as the public class adding the extension ".java" (eg, A common error is to use a different name for the file and the class. The name before the "." must be the same as the class name, including upper- or lowercase. Many programmers save their source file every 10 minutes or so -- it's quick and saves the aggravation of having to type it again if there is a system crash.
  2. Open a DOS command window and cd to the directory containing the source file. This is easy if you've used short directory names without spaces.
  3. Compile the source program ( in this example) with the following DOS command:
  4. This produces one or more ".class" files, which are the object (Java byte code) form of Java programs. You can produce a ".exe" file from this, but that isn't normally done.
  5. Run it with:
    java Greeting
    This loads the Greeting.class file and all necessary classes. Execution starts with the main method in the Greeting class.
Continue in this cycle until the program works.