/**
 * Models ants living in a 1-dimensional world.<br>
 * A queen ant can make a bunch of ants and spread them around in a
 * 1-dimensional world.  An ant from a particular colony can always calculate
 * its distance from its queen.  An ant can also move its queen to a different
 * location.  Wherever the queen moves to, her ants always know how their
 * relative distance from her.<br>
 * The above is modeled by a <code>Queen</code> class with an abstract
 * <code>Ant</code> inner class.
 * The <code>Ant<code> inner objects has direct access to the location of its
 * outer <code>Queen</code> object.
 * @author S.B. Wong
 * @author D.X. Nguyen
 */
public class Queen {

    private int origin;  // what does it mean for origin to be static?

    /**
     * Is part of a <code>Queen</code> instance, just like the
     * <code>origin</code> field and the <code>makeAnt()</code> method are
     * parts of a Queen instance.
     */
    public abstract class Ant {

        public abstract int calcDist();

        public void moveQueen(int origin) {
            Queen.this.origin = origin;
        }
    }

    public Queen(int origin) {
        this.origin = origin;
    }

    /**
     * Factory method: relegate the task of manufacturing concrete Ant objects
     * to the Queen object because the Queen object intrinsically "knows" how
     * to make its inner objects.
     */
    public Ant makeAnt(final int loc){
        return new Ant() {              // Anonymously created Ant object
            public int calcDist(){      // overriding calcDist.  As long as this
                return loc - origin;    // object is alive, the value of loc
            }                           // stays with it and does not change.
        };
    }
}

/**
 * Test class for used with DrJava.
 <pre>
 // After compiling, enter the following in the interactions window.
 TestQueen.vicAnt1.calcDist()
 TestQueen.vicAnt2.calcDist()
 TestQueen.lizAnt1.calcDist()
 TestQueen.lizAnt2.calcDist()

 // Now move the queens around:
 TestQueen.lizAnt2.moveQueen(0)
 TestQueen.vicAnt1.moveQueen(-1)

 // Check the distance again:
 TestQueen.vicAnt1.calcDist()
 TestQueen.vicAnt2.calcDist()
 TestQueen.lizAnt1.calcDist()
 TestQueen.lizAnt2.calcDist()
 </pre>
 */
class TestQueen{
    public static Queen vicky = new Queen(10);
    public static Queen lizzy = new Queen(-10);
    public static Queen.Ant vicAnt1 = vicky.makeAnt(5);
    public static Queen.Ant vicAnt2 = vicky.makeAnt(-7);
    public static Queen.Ant lizAnt1 = lizzy.makeAnt(-6);
    public static Queen.Ant lizAnt2 = lizzy.makeAnt(2);
}