Writing My First Java Program

Java Tutorials - Herong's Tutorial Notes

Dr. Herong Yang, Version 6.00

∟Writing My First Java Program

This section provides a tutorial example on how to write, compile, and execute the first Java program with JDK 1.5.0. Notes were taken in 2007.

When JDK is installed on your machine, it provides two commands for you to compile and run Java programs.

"javac class_name.java" - Compiles a Java program stored a file named with the program class name.
"java -cp . class_name" - Runs a compiled Java program. "-cp ." specifies the current directory as the class path.

Let's try these commands with a very simple Java program. Use NotePad to enter the following Java program into a file called Hello.java:

class Hello {
   public static void main(String[] a) {
      System.out.println("Hello world!"); 	
   }
}

Then compile this program in a command window with the "javac" command:

C:\>\progra~1\java\jdk1.6.0_02\bin\javac Hello.java

To execute the program, use the java command:

C:\>\progra~1\java\jdk1.6.0_02\bin\java Hello
Hello world!

Congratulations, you have successfully entered, compiled and executed your first Java program.

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Dr. Herong Yang, updated in 2008

Writing My First Java Program