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Clarify... Wrapper Classes...

 
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Integer i = new Integer (42);
Long l = new Long (42);
Double d = new Double (42.0);

Which expressions evaluate to True?
A. (i == l)
B. (i == d)
C. (d == l)
D. (i.equals (d))
E. (d.equals (i))
F. (i.equals (42))
G. (i.equals (l))
H. (l.equals (d))
 
Ranch Hand
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I assume you're using 1.5.

The equals methods in Integer, Long, and Double will not return true if the parameter to equals is not the correct class.

So I would guess f is the only one that is true. But you can type in a test class and determine if that's right.
 
Shiaber Shaam
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Need still more clarifications..............
 
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A. (i == l) //compile-time error
B. (i == d) //compile-time error
C. (d == l) //compile-time error
D. (i.equals(d)) //false because d is not an instance of Integer
E. (d.equals(i)) //false because i is not an instance of Double
F. (i.equals(42))//true
G. (i.equals(l)) //false because l is not an instance of Integer
H. (l.equals(d)) //false because d is not an instance of Long
 
Greenhorn
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A. (i == l) //compiler error, compare objects of different class
B. (i == d) //compiler error, compare objects of different class
C. (d == l) //compiler error, compare objects of different class
D. (i.equals (d)) //false, compare objects of different class
E. (d.equals (i)) //false, compare objects of different class
F. (i.equals (42)) //true, 42 autoboxing to Integer and then compare contents
G. (i.equals (l)) //false, compare objects of different class
H. (l.equals (d)) //false, compare objects of different class

Method equals() for Wrapper classes always return false if compared objects diffrents class
P.S Sorry for bad English
 
Shiaber Shaam
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Thanks for your Posts.....
 
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