Java OCA OCP Practice Question 2373

Question

Given: 

public class Main {
   public static void main(String... args) {
      Boolean buy = new Boolean(true);
      Boolean sell = new Boolean(true);
      System.out.print(buy == sell);

      boolean buyPrim = buy.booleanValue();
      System.out.print(!buyPrim);

      System.out.print(buy && sell);
   }//from  w  w w .j a v  a2  s. c  o  m
}

What is the output? 

a  falsefalsefalse
b  truefalsetrue
c  falsetruetrue
d  falsefalsetrue
e  Compilation error
f  Runtime exception



d

Note

The Boolean instances buy and sell are created using constructors.

Constructors don't refer to existing instances in cache; they create new instances.

Because the comparison operator == compares object references and not the primitive value stored by a wrapper instance, buy == sell returns false.

The method booleanValue() can be used to get the primitive boolean value stored by a Boolean wrapper instance.

So buy.booleanValue() returns false.

Because wrapper instances can be used with arithmetic and logical operators, buy && sell compiles, returning true.




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