About Wrapper classes.

[Michael Zhang]

Consider the following variables definitions.
Float f1 = new Float("10F");
Float f2 = new Float("10F");
Double d1 = new Double("10D");
Which of the following yields a boolean value of true.
a)f1 == f2
b)f1.equals(f2)
c)f2.equals(d1)
d)f2.equals(new Float("10"))
ANS: b,d
c is incorrect. why answer c returns false?

[dragon ji]

the equals method at wraper class will return true only if the argument is not null and is a same object that represents the same value as this object.

[Abu Yoosuf]

The equals() method defined in the java.lang.Float class is copied below.

 
public boolean equals(Object obj) {
        //just showing the part we need
return (obj instanceof Float) && ... ;
}
 

In order to return true for an equality check, first of all, the object must be an instance of class Float.
[ December 05, 2002: Message edited by: Abu Yoosuf ]
[ December 05, 2002: Message edited by: Abu Yoosuf ]
[ December 05, 2002: Message edited by: Abu Yoosuf ]