#vulnerable code 
                             @Test
	public void nullAndEmpty() {
		// toJson测试 //

		// Null Bean
		TestBean nullBean = null;
		String nullBeanString = binder.toJson(nullBean);
		assertEquals("null", nullBeanString);

		// Empty List
		List<String> emptyList = Lists.newArrayList();
		String emptyListString = binder.toJson(emptyList);
		assertEquals("[]", emptyListString);

		// fromJson测试 //

		// Null String for Bean
		TestBean nullBeanResult = binder.fromJson(null, TestBean.class);
		assertNull(nullBeanResult);

		nullBeanResult = binder.fromJson("null", TestBean.class);
		assertNull(nullBeanResult);

		// Null/Empty String for List
		List nullListResult = binder.fromJson(null, List.class);
		assertNull(nullListResult);

		nullListResult = binder.fromJson("null", List.class);
		assertNull(nullListResult);

		nullListResult = binder.fromJson("[]", List.class);
		assertEquals(0, nullListResult.size());
	} 
                            #location 32 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             @Test
	public void nullAndEmpty() {
		// toJson测试 //

		// Null Bean
		TestBean nullBean = null;
		String nullBeanString = binder.toJson(nullBean);
		assertThat(nullBeanString).isEqualTo("null");

		// Empty List
		List<String> emptyList = Lists.newArrayList();
		String emptyListString = binder.toJson(emptyList);
		assertThat(emptyListString).isEqualTo("[]");

		// fromJson测试 //

		// Null String for Bean
		TestBean nullBeanResult = binder.fromJson(null, TestBean.class);
		assertThat(nullBeanResult).isNull();

		nullBeanResult = binder.fromJson("null", TestBean.class);
		assertThat(nullBeanResult).isNull();

		// Null/Empty String for List
		List nullListResult = binder.fromJson(null, List.class);
		assertThat(nullListResult).isNull();

		nullListResult = binder.fromJson("null", List.class);
		assertThat(nullListResult).isNull();

		nullListResult = binder.fromJson("[]", List.class);
		assertThat(nullListResult).isEmpty();
	}