HEMANT SONKER'S BLOG

Wednesday, October 15, 2008

Running a Java Program from Command Prompt

  • Create a temporary folder C:\mywork. Using Notepad or another text editor, create a small Java file Hello.java with the following text:
     class Hello
    {
    public static void main(String[] args)
    {
    System.out.println("Hello, World!");
    }
    }

    Save your file as Hello.java in C:\mywork. To make sure your file name is Hello.java, (not Hello.java.txt), first choose "Save as file type:" All files, then type in the file name Hello.java.

  • Run Command Prompt (found under All Programs/Accessories in the Start menu). Type
    C:\> cd \javaprog
    This makes C:\mywork the current directory.
    C:\javaprog> dir
    This displays the directory contents. You should see HelloWorld.java among the files.
    C:\javaprog> set path=%path%;C:\Program Files\Java\jdk1.5.0_09\bin
    This tells the system where to find JDK programs.
    C:\javaprog> javac Hello.java
    This runs javac.exe, the compiler. You should see nothing but the next system prompt...
    C:\javaprog> dir
    javac has created the Hello.class file. You should see Hello.java and HelloWorld.class among the files.
    C:\javaprog> java Hello
    This runs the Java interpreter. You should see the program output:
    Hello, World!

    If the system cannot find javac, check the set path command. If javac runs but you get errors, check your Java text. If the program compiles but you get an exception, check the spelling and capitalization in the file name and the class name and the java Hello command. Java is case-sensitive!

  • It is possible to make the path setting permanent but you have to be very careful because your system might crash if you make a mistake.

Click "Edit" and at the end append

;C:\Program Files\Java\jdk1.5.0_09\bin

(or the path to the appropriate folder where the latest version of JDK is installed). Do not put spaces before the appended path string.

Click OK on the path edit box and OK on the Ennvironment Variables box. The new setting will go into effect next time you run Command Prompt.

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