Modify the LabeledPoint class of of Exercise P16.12 so that it implements the Co

Question

Modify the LabeledPoint class of of Exercise P16.12 so that it implements the Comparable interface. Sort points first by their x-coordinates. If two points have the same x-coordinate, sort them by their y-coordinates. If two points have the same x- and y-coordinates, sort them by their label. Write a tester program that checks all cases.

16.12
A labeled point has x- and y-coordinates and a string label. Provide a class LabeledPoint with a constructor LabeledPoint(int x, int y, String label) and hashCode and equals methods. Two labeled points are considered the same when they have the same location and label.

Explanation / Answer

public class LabeledPoint implements Comparable<LabeledPoint>
{
    private double x,y;
    private String label;

    ...


    public int compareTo(LabeledPoint rhs)
    {
        if(rhs.x != x)
        {
            if(x < rhs.x)
                return -1;
            else
                return 1;
        }
        else if(rhs.y != y)
        {
            if(y < rhs.y)
                return -1;
            else
                return 1;
        }
        else
        {
            return label.compareTo(rhs.label);
        }
    }
}

I leave the test class up to you - making test cases is trivial.

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