An immutable Point class to limits bounds to [-10, 10]

Point10.java

// A point class must be immutable

class Point
{
    public final double x;
    public final double y;

    public Point(double x, double y)
    {
	this.x = x;
	this.y = y;
    }

    public Point(Point p)
    {
	this.x = p.x;
	this.y = p.y;
    }

    public String toString()
    {
	return new StringBuilder()
	    .append('[')
	    .append(x)
	    .append(',')
	    .append(y)
	    .append(']')
	    .toString();
    }
}

public final class Point10
    extends Point
{
    public Point10(double x, double y)
    {
	super(checkBounds(x), checkBounds(y));
    }

    public Point10(Point p)
    {
	this(p.x, p.y);
    }

    public Point10(Point10 p)
    {
	// Bypass checks
	super(p.x, p.y);
    }

    private static final double checkBounds(double coord)
    {
	if (coord < -10 || coord > 10)
	    throw new IllegalArgumentException("value out of bounds");
	return coord;
    }



    // Example code
    public static void main(String[] args)
    {
	System.out.println(new Point10(4.0, 8.0));
	System.out.println(new Point10(4.0, 18.0));
    }
}