Wrapper classes

[Li Wenfeng]

2. Given:
Integer i = new Integer (42);
Long 1 = new Long (42);
Double d = new Double (42.0);
Which two expressions evaluate to True? (Choose Two)
A. (i ==1)
B. (i == d)
C. (d == 1)
D. (i.equals (d))
E. (d.equals (i))
F. (i.equals (42))
I was given the answer D,E. But both D and E result in "false", because english is not my native language, so maybe I misunderstanded the question sentence: "evaluate to True", does it mean "which two of the options could be compiled fine?" rather than "get result of "true""?
thanks!

[Alfred Kemety]

The answer given is WRONG, all the cases evaluate to false. In wrapper classes, if the argument passed in the equal() method is of a different run-time type, then the equals method returns false. The following code prints false 3 times.

public class Test {
public static void main(String[] args) {
Integer i = new Integer (42);
Long l = new Long (42);
Double d = new Double (42.0);
System.out.println(i.equals(l));
System.out.println(l.equals(i));
System.out.println(d.equals(l));
}
}

[ October 29, 2002: Message edited by: Alfred Kemety ]