Code Wont Run, Got Strange Error [closed]

You seem to be mis-understanding the basics of Java syntax. Specifically, you cannot define your class’s members and methods inside main() the way you are attempting to do:

import java.awt.*;
public class Alien {
    public static void main(String[] args) {
        // TODO Auto-generated method stub

        /**
         * The Alien class. 
         */


            public static int ALIEN_HEIGHT = 25;  // you can't put this here
            public static int ALIEN_WIDTH = 15;   // you can't put this here

            private int leftPosition = 0;         // you can't put this here
            private int heightPosition = 0;       // you can't put this here
            //etc

To get this to compile, you need to close main() and delete all the extra } you have at the end of your code:

import java.awt.*;

public class Alien {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
    }

    /**
     * The Alien class. 
     */
    public static int ALIEN_HEIGHT = 25;
    public static int ALIEN_WIDTH = 15;
    //etc

You’ll also need to add some code to main() before your program actually does anything.

I would suggest that before you continue your current program you read some of the excellent tutorials online. A good place to start is The Java™ Tutorials on the oracle website.

Look at the Trails Covering the Basics section and work your way through Getting Started and Learning the Java Language before doing anything else.