ParticleVector { public Double getX() { return list.get(0); } ParticleVector();  ParticleVector(double vectorX, double vectorY); void add(ParticleVector vector); void set(double vectorX, double vectorY); Double getX(); Double getY(); @Override boolean equals(Object object); @Override int hashCode();  }
@Test public void testGetX() { ParticleVector vector1 = new ParticleVector(); Assert.assertEquals(0.0, vector1.getX(), 0.001); vector1 = new ParticleVector(10, 10); Assert.assertEquals(10, vector1.getX(), 0.001); }