public class HashCodeTest {
	public static void main(String[] args) {
		Collection set = new HashSet();
		Point p1 = new Point(1, 1);
		Point p2 = new Point(1, 2);

		set.add(p1);
		set.add(p2);
		
		p2.setX(10);
		p2.setY(10);
		
		set.remove(p2);

		Iterator iterator = set.iterator();
		while (iterator.hasNext()) {
			Object object = iterator.next();
			System.out.println(object);
		}
	}
}

class Point {
	private int x;
	private int y;

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


	public int getX() {
		return x;
	}


	public void setX(int x) {
		this.x = x;
	}


	public int getY() {
		return y;
	}


	public void setY(int y) {
		this.y = y;
	}


	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + x;
		result = prime * result + y;
		return result;
	}


	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		Point other = (Point) obj;
		if (x != other.x)
			return false;
		if (y != other.y)
			return false;
		return true;
	}


	@Override
	public String toString() {
		return "x:" + x + ",y:" + y;
	}

}
 

x:1,y:1
x:10,y:10