Mastering Java: The Ultimate Quiz for 'Thinking in Java'

For object reference comparison, which operators are used?

1. == and !=

2. equals() and !equals()

3. hashCode() and !hashCode()

4. == and ===

The correct answer is: == and !=

Certain operators like the == and != do not compare the contents of objects, but rather the memory reference/address. This means these operators simply check if the objects being compared are the same object, not if they have the same content. The equals() and !equals() methods are used for content comparison, but these are not operators. The hashCode() and !hashCode() methods simply return unique hash codes for objects, they do not compare objects. The === operator is not a valid Java operator. Therefore, the correct answer is A as it correctly identifies the operators used for object reference comparison.