Writing a Java Program

Java source code is written in plain text, using a text editor.

• This could range from a plain text editor like Notepad, to a programmers' editor such as TextPad, EditPlus, or Crimson Editor, to a complex integrated development environment (IDE) like NetBeans, Eclipse, or JDeveloper.
• The source code file should have a .java extension.

The javac compiler is then used to compile the source code into bytecode.

1	javac MyClass.java

• The bytecode is stored in a file with an extension .class
• Bytecode is universal - one bytecode file will run on any supported platform.

You then run the java runtime engine, which will then interpret the bytecode to execute the program.

1	java MyClass

• The executable program you are running is: java.
• The class name tells the JVM what class to load and run the main method for.
• You must have a JVM made specifically for your hardware/OS platform.