CORE JAVA Interview Questions-part 7

Question: How are commas used in the intialization and iteration parts of a for statement?

Answer: Commas are used to separate multiple statements within the initialization and iteration parts of a for statement.

Question: What is an abstract method?

Answer: An abstract method is a method whose implementation is deferred to a subclass.

Question: What value does read() return when it has reached the end of a file?

Answer: The read() method returns -1 when it has reached the end of a file.

Question: Can a Byte object be cast to a double value?

Answer: No, an object cannot be cast to a primitive value.

Question: What is the difference between a static and a non-static inner class?

Answer: A non-static inner class may have object instances that are associated with instances of the class's outer class. A static inner class does not have any object instances.

Question: If a variable is declared as private, where may the variable be accessed?

Answer: A private variable may only be accessed within the class in which it is declared.

Question: What is an object's lock and which object's have locks?

Answer: An object's lock is a mechanism that is used by multiple threads to obtain synchronized access to the object. A thread may execute a synchronized method of an object only after it has acquired the object's lock. All objects and classes have locks. A class's lock is acquired on the class's Class object.

Question: What is the % operator?

Answer: It is referred to as the modulo or remainder operator. It returns the remainder of dividing the first operand by the second operand.



Question: When can an object reference be cast to an interface reference?

Answer: An object reference be cast to an interface reference when the object implements the referenced interface.

Question: Which class is extended by all other classes?

Answer: The Object class is extended by all other classes.

Question: Can an object be garbage collected while it is still reachable?

Answer: A reachable object cannot be garbage collected. Only unreachable objects may be garbage collected.