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  1. class Point {
  2. 	protected int x, y;
  3.  
  4. 	public boolean equals(Object o) {
  5. 		if (!(o instanceof Point)) return false;
  6. 		Point other = (Point)o;
  7. 		return other.x == x && other.y == y;
  8. 	}
  9.  
  10. 	public int hashCode() {
  11. 		return x * 31 + y;
  12. 	}
  13. }
  14.  
  15. class ColoredPoint extends Point {
  16. 	protected int color;
  17.  
  18. 	public boolean equals(Object o) {
  19. 		if (!(o instanceof ColoredPoint)) return false;
  20. 		ColoredPoint cp = (ColoredPoint) o;
  21. 		return super.equals(o) && cp.color == color;
  22. 	}
  23.  
  24. 	public int hashCode() {
  25. 		return super.hashCode() * 31 + color;
  26. 	}
  27. }
  28.  
  29. class BuggyInit {
  30. 	public static void main (String[] args) {
  31. 		Point center = new Point();
  32. 		ColoredPoint white = new ColoredPoint();
  33. 		ColoredPoint red = new ColoredPoint();
  34. 		red.color = 0xff0000;
  35.  
  36. 		System.out.println("center == white ? " + center.equals(white));
  37. 		System.out.println("center == red ? " + center.equals(red));
  38. 		System.out.println("Well, center == white, center == red, so, white == red, isn't it ? " + white.equals(red));
  39. 		System.out.println("Hm... center == white, so white == center, I'm sure.  " + white.equals(center));
  40. 	}
  41. }
Success #stdin #stdout 0.07s 380224KB
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Standard input is empty
stdout
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center == white ? true
center == red ? true
Well, cented == white, center == red, so, white == red, isn't it ? false
Hm... center == white, so white == center, I'm sure.  false
https://ideone.com/TShTlc
language:
Java (HotSpot 12)
created:
12 years ago
visibility:
public

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