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我正在阅读J. Bloch的有效Java并需要刷新equals
/hashCode
合同和关系。测试重写等于方法
我有以下的JavaBean类:
public class MyJavaBean{
private int id;
private Properties fItem; //Enumeration type
private String value;
private Rule rule; //Enumeration type
private int fId;
//GET, SET
@Override
public boolean equals(Object o){
if(!(o instanceof MyJavaBean))
return false;
MyJavaBeanv = (MyJavaBean) o;
return (fItem == null ? v.fItem == null : fItem.equals(v.fItem)) &&
(value == null ? v.value == null : value.equals(v.value)) &&
(rule == null ? v.rule == null : rule.equals(v.rule)) &&
fId == v.fId && id == v.id;
}
@Override
public int hashCode(){
int result = 17;
if(fItem != null)
result = 31 * result + fItem.hashCode();
if(value != null)
result = 31 * result + value.hashCode();
if(rule != null)
result = 31 * result + rule.hashCode();
result = 31 * result + fId;
result = 31 * result + id;
return result;
}
}
他还建议我们写单元测试,以确保合同实际上是满意的。这就是他所说的(斜体粗体强调雷):
当你写完你的equals方法,问自己三个 问题:它是对称的?它是传递性的吗?它一致吗?和 不只是问问自己; 编写单元测试检查这些 属性是否成立!
所以,我无法想象如何为这个非常简单的情况编写单元测试。好吧,我会写这样的事情:
public class MyTest{
//Each pair consists of the equals object
private Map<MyJavaBean, MyJavaBean> equalValueMap;
@Before
public void init(){
//initializing the map, using ThredLocalRandom
//to get ints and enums randomly
}
@Test
public void testReflexive(){
for(MyJavaBean fiv: equalValueMap.keySet()){
Assert.assertEquals(fiv.equals(fiv), true);
}
}
@Test
public void testSymmetric(){
for(MyJavaBean fiv: equalValueMap.keySet()){
Assert.assertEquals(equalValueMap.get(fiv).equals(fiv), true);
Assert.assertEquals(fiv.equals(equalValueMap.get(fiv)), true);
}
}
@Test
public void testHashCode(){
for(FilterItemValue fiv: equalFilterValueMap.keySet()){
Assert.assertEquals(equalFilterValueMap.get(fiv).hashCode(), fiv.hashCode());
}
}
}
但我认为这样的测试只是浪费构建时,因其简单而意义。为简单的JavaBeans的方法编写测试值得吗?