Object比较 - 未名空间MITBBS历史存档

国际科技财经博客移民网络热点娱乐民生时事公众号

Redian新闻

>未名空间

>Java - 爪哇娇娃

Object比较

Object比较# Java - 爪哇娇娃

s*y2006-12-18 08:12

1 楼

我记得== 只适用于数值比较
对于Object, 要用 a.equal(b)来进行比较
那么对于下面的的code, "==" 应该返回不等; "e . equal ( f )"应该返回相等
可运行的结果却是两个都不相等
== shows e and f are not equal
e . equal ( f ) shows they are not equal
这是什么原因? 谢谢

B*h2006-12-18 08:12

2 楼

o1 == o2 : only when o1 and o2 are the same object.
o1.equals(o2): implemented as {return o2 ==null ? false : o1 == o2;}by defau
lt in Object class.

【在 s******y 的大作中提到】

: 我记得== 只适用于数值比较
: 对于Object, 要用 a.equal(b)来进行比较
: 那么对于下面的的code, "==" 应该返回不等; "e . equal ( f )"应该返回相等
: 可运行的结果却是两个都不相等
: == shows e and f are not equal
: e . equal ( f ) shows they are not equal
: 这是什么原因? 谢谢

s*y2006-12-18 08:12

3 楼

e.equal(f) 在这个case里, 依你说, 是应该等还是不等呢?

defau

【在 B*********h 的大作中提到】

: o1 == o2 : only when o1 and o2 are the same object.
: o1.equals(o2): implemented as {return o2 ==null ? false : o1 == o2;}by defau
: lt in Object class.

B*h2006-12-18 08:12

4 楼

were you reading my post?

【在 s******y 的大作中提到】

: e.equal(f) 在这个case里, 依你说, 是应该等还是不等呢?
:
: defau

m*y2006-12-18 08:12

5 楼

你要在Officer class里override那个equals方法
只有你自己知道应该怎么判断相等的标准
否则by default用==比较就是不相等

【在 s******y 的大作中提到】

s*y2006-12-18 08:12

6 楼

Of course, but still a little confused, from what you said
e.equal(f) still should be true.
But why did the code return false instead

【在 B*********h 的大作中提到】

: were you reading my post?

B*h2006-12-18 08:12

7 楼

how are e and f THE same object?
e = new Officer(...);
f = new Officer(...);
different objects.

【在 s******y 的大作中提到】

: Of course, but still a little confused, from what you said
: e.equal(f) still should be true.
: But why did the code return false instead

m*y2006-12-18 08:12

8 楼

As BulletTooth said,
the default impl of equals is
public boolean equals(Object obj) {
return (this == obj);
}
If u don't override, u will always get "false"...

【在 s******y 的大作中提到】

: Of course, but still a little confused, from what you said
: e.equal(f) still should be true.
: But why did the code return false instead

s*y2006-12-18 08:12

9 楼

I see. Thanks you guys

【在 m******y 的大作中提到】

: As BulletTooth said,
: the default impl of equals is
: public boolean equals(Object obj) {
: return (this == obj);
: }
: If u don't override, u will always get "false"...

s*y2006-12-18 08:12

10 楼

thanks a lot.

【在 B*********h 的大作中提到】

: how are e and f THE same object?
: e = new Officer(...);
: f = new Officer(...);
: different objects.