### Question:
Bubble extends Point<Bubble> { boolean touches(Bubble b) { return (this.coordinateX - b.coordinateX) * (this.coordinateX - b.coordinateX) + (this.coordinateY - b.coordinateY) * (this.coordinateY - b.coordinateY) <= (this.radius + b.radius) * (this.radius + b.radius); } Bubble(int x, int y, int id, int radius);   }### Answer:
@Test void touchesTest() { var b1 = new Bubble(0, 0, 1, 2); var b2 = new Bubble(1, 1, 2, 1); var b3 = new Bubble(10, 10, 3, 1); assertTrue(b1.touches(b2)); assertFalse(b1.touches(b3)); }