Java OCA OCP Practice Question 608

Question

What is the result of executing the following fragment of code: 

boolean b1 = false; 
boolean b2 = false; 
if  (b2  != b1 =  !b2){ 
   System.out.println ("true"); 
} 
else{ 
   System.out.println ("false"); 
}

Select 1 option

  • A. Compile time error.
  • B. It will print true.
  • C. It will print false.
  • D. Runtime error.
  • E. It will print nothing. 


Correct Option is  : A

Note

Note that boolean operators have more precedence than =.

In (b2 != b 1 = !b2) first b2 != b 1 is evaluated which returns a value 'false'.

So the expression becomes false = !b2.

And this is illegal because false is a value and not a variable!

Had it been something like (b2 = b1 != b2)

then it is valid because it will boil down to : b2 = false.

Because all an if() needs is a boolean, now b1 != b2 returns false which is a boolean and as b2 = false is an expression and every expression has a return value which is actually the Left Hand Side of the expression.

Here, it returns false, which is again a boolean.

Note that return value of expression : i = 10 , where i is an int, is 10, which is an int.




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