Boolean.TRUE == myBoolean vs. Boolean.TRUE.equals(

问题:

Is there ever a situation where using equals(Boolean) and == would return different results when dealing with Boolean objects?

Boolean.TRUE == myBoolean;

Boolean.TRUE.equals(myBoolean);

I'm not thinking about primitive types here, just Boolean objects.

回答1:

How about:

System.out.println(new Boolean(true) == new Boolean(true));
System.out.println(new Boolean(true) == Boolean.TRUE);

(both print false, for the same reason as any other type of objects).

回答2:

It would be dangerous to use == because myBoolean may not have originated from one of the constants, but have been constructed as new Boolean(boolValue), in which case == would always result in false. You can use just

myBoolean.booleanValue()

with neither == nor equals involved, giving reliable results. If you must cater for null-values as well, then there's nothing better than your equals approach.

回答3:

== only works for primitive types
when you compare Objects you should always use o.equls(Object ob)

回答4:

     if(Boolean.TRUE == new Boolean(true)){
            System.out.println("==");
        }

        if(Boolean.TRUE.equals(myBoolean)){
            System.out.println("equals");;
        }

In this case first one is false. Only second if condition is true. Prints :

equals