### Question:
Bubble extends Point<Bubble> { void pop(Hashtable<Integer, Bubble> allBubbles) { LOGGER.info("Bubble " + this.id + " popped at (" + this.coordinateX + "," + this.coordinateY + ")!"); allBubbles.remove(this.id); } Bubble(int x, int y, int id, int radius);   }### Answer:
@Test void popTest() { var b1 = new Bubble(10, 10, 1, 2); var b2 = new Bubble(0, 0, 2, 2); var bubbles = new Hashtable<Integer, Bubble>(); bubbles.put(1, b1); bubbles.put(2, b2); b1.pop(bubbles); assertNull(bubbles.get(1)); assertNotNull(bubbles.get(2)); }