### Question:
StrokeMap implements Cloneable, Serializable { public Stroke getStroke(Comparable key) { ParamChecks.nullNotPermitted(key, "key"); return this.store.get(key); } StrokeMap(); Stroke getStroke(Comparable key); boolean containsKey(Comparable key); void put(Comparable key, Stroke stroke); void clear(); @Override boolean equals(Object obj); @Override Object clone();  }### Answer:
@Test public void testGetStroke() { StrokeMap m1 = new StrokeMap(); assertEquals(null, m1.getStroke("A")); m1.put("A", new BasicStroke(1.1f)); assertEquals(new BasicStroke(1.1f), m1.getStroke("A")); m1.put("A", null); assertEquals(null, m1.getStroke("A")); try { m1.getStroke(null); fail("IllegalArgumentException should have been thrown on null argument"); } catch (IllegalArgumentException e) { assertEquals("Null 'key' argument.", e.getMessage()); } }