Java Interview Questions and Answers for Written Exam and Interview

Java Interview

Ques : What is the difference between the String and StringBuffer classes?

String objects are constants. StringBuffer objects are not.

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

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

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

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.

Ques : What is the Dictionary class?

The Dictionary class provides the capability to store key-value pairs.

Ques : How are the elements of a BorderLayout organized?

The elements of a BorderLayout are organized at the borders (North, South, East, and West) and the center of a container.

Ques : What is the % operator?

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

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

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

Ques : What is the difference between a Window and a Frame?

The Frame class extends Window to define a main application window that can have a menu bar.

Ques : Which class is extended by all other classes?

The Object class is extended by all other classes.

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

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