java.util.Date的行为

Question

Foo a;
...
Date b = a.getDate();
Date c = new Date(b.getTime());

if (b.equals(c)) System.out.println("equal");
else System.out.println("not equal");

System.out.println(b.toString());
System.out.println(b.getTime());
System.out.println(c.toString());
System.out.println(c.getTime());

以上打印:

not equal
2011-07-23 22:24:21.834
1311459861834
Sat Jul 23 22:24:21
1311459861834

为什么是这样？这是日期中的错误吗？这很难相信.

Answer 1

a.getDate() 明显回归 java.sql.Timestamp

java.sql.Timestamp有java.uti.Date基本上不同的等于方法

return obj instanceof Date && getTime() == ((Date) obj).getTime();

Timestamp然而,它更复杂,它也需要目标Timestamp.

if (ts instanceof Timestamp) {
    return this.equals((Timestamp)ts);//the impl checks nanos too
  } else {
    return false;
  }

你可能使用Hibernate或者类似的东西,持续java.util.Date的Timestamp.