doubt in boxing

[Tashi Rautela]

public class Boxing6 {
public static void main(String[] args) {
Boolean b1 = new Boolean(true);
Boolean b2 = new Boolean(true);
boolean b3 = true;
Boolean b4 = true;
System.out.println(b1==b2);
System.out.println(b1==b3);
System.out.println(b3 == b4);
System.out.println(b1 == b4);
}
}

the answer is false true true false how??? anyone please explain

[Vassili Vladimir]

Hi,

The first if statement is checking for the references, and since each object refers to a different object on the heap, you'll get false.

The second if statement automatically un-boxes b1 and compares it with b3 which is true, so you'll get true.

The third if statement automatically un-boxes b4 (which was automatically boxed) and compares it with b3 which is true, so you'll get true.

The fourth statement is also checking for references (because, remember, b4 is an automatic boxing), so you'll get false.

Best of luck ...

[Quintin Stephenson]

Hi Tashi

Read the following forum:
http://www.coderanch.com/t/262155/java-programmer-SCJP/certification/equals


It deals with the same set of topics (shallow vs. deep comparisons and autoboxing)

Cheers
Q

[Chandra Bhatt]

public class Boxing6 {
public static void main(String[] args) {
Boolean b1 = new Boolean(true);
Boolean b2 = new Boolean(true);
boolean b3 = true;
Boolean b4 = true;
System.out.println(b1==b2); //different references results false
System.out.println(b1==b3); //Wrapper Boolean is converted into primitive
//boolean before comparison, result true
System.out.println(b3 == b4); //b4 is unboxed to primitive before comparison
System.out.println(b1 == b4); //again reference comparison, false because
//both are different
}
}

Thanks,

[Tashi Rautela]

thanks to all...understood