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Java Online Quiz

Following quiz provides Multiple Choice Questions (MCQs) related to Core Java. You will have to read all the given answers and click over the correct answer. If you are not sure about the answer then you can check the answer using Show Answer button. You can use Next Quiz button to check new set of questions in the quiz.

Q 1 - Which of the following is not a keyword in java?

Answer : B

Explaination

Boolean is a class and is not a keyword.

Q 2 - What is the size of char variable?

Answer : B

Explaination

The char data type is represented by single 16-bit Unicode character.

Minimum value: '\u0000' (or 0)

Maximum value: '\uffff' (or 65,535)

Q 3 - What is the default value of String variable?

Answer : C

Explaination

String variable has default value of null if defined as an instance/static variable.

Q 4 - Which of the following is true about protected access modifier?

A - Variables, methods and constructors which are declared protected can be accessed by any class.

B - Variables, methods and constructors which are declared protected can be accessed by any class lying in same package.

C - Variables, methods and constructors which are declared protected in the superclass can be accessed only by its child class.

D - None of the above.

Answer : B

Explaination

Variables, methods, and constructors which are declared protected can be accessed by any class lying in the same package.

Q 5 - What is instance variable?

A - Instance variables are static variables within a class but outside any method.

B - Instance variables are variables defined inside methods, constructors or blocks.

C - Instance variables are variables within a class but outside any method.

D - None of the above.

Answer : C

Explaination

Instance variables are variables within a class but outside any method. These variables are instantiated when the class is loaded.

Q 6 - Composition represents

A - HAS-A relationship.

B - IS-A relationship.

Answer : A

Explaination

Holding the reference of the other class within some other class is known as composition. It represents a HAS-A relationship. For example, a Student has a Pen. Here Student class has Pen as its instance variable.

Q 7 - What is NullPointerException?

A - A NullPointerException is thrown when calling the instance method of a null object or modifying/accessing field of a null object.

B - A NullPointerException is thrown when object is set as null.

C - A NullPointerException is thrown when object property is set as null.

D - None of the above.

Answer : A

Explaination

A NullPointerException is thrown when calling the instance method of a null object or modifying/accessing field of a null object.

Q 8 - Which is the way in which a thread can enter the waiting state?

A - Invoke its sleep() method.

B - invoke object's wait method.

C - Invoke its suspend() method.

D - All of the above.

Answer : D

Explaination

A thread can enter the waiting state by invoking its sleep() method, by blocking on IO, by unsuccessfully attempting to acquire an object's lock, or by invoking an object's wait() method. It can also enter the waiting state by invoking its (deprecated) suspend() method.

Q 9 - Can constructor be inherited?

A - True.

B - False.