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 - What is a class in java?
B - class is a special data type.
Answer : A
Explaination
A class is a blue print from which individual objects are created. A class can contain fields and methods to describe the behavior of an object.
Answer : A
Explaination
True, a java file can contain one public class and many other non-public classes.
Answer : A
Explaination
double variable has default value of 0.0d if defined as an instance/static variable.
Q 4 - Which of the following stands true about default modifier of class members?
A - By default, variables, methods and constructors can be accessed by subclass only.
Answer : C
Explaination
By default, variables, methods and constructors can be accessed by any class lying in the same package.
Q 5 - What is an immutable object?
A - An immutable object can be changed once it is created.
B - An immutable object can't be changed once it is created.
C - An immutable object is an instance of an abstract class.
Answer : B
Explaination
An immutable object can't be changed once it is created. String objects are immutable.
Q 6 - What is JRE?
A - JRE is a java based GUI application.
B - JRE is an application development framework.
C - JRE is an implementation of the Java Virtual Machine which executes Java programs.
Answer : C
Explaination
Java Runtime Environment is an implementation of the Java Virtual Machine which executes Java programs. It provides the minimum requirements for executing a Java application.
Q 7 - What is function overloading?
A - Methods with same name but different parameters.
B - Methods with same name but different return types.
C - Methods with same name, same parameter types but different parameter names.
Answer : A
Explaination
If a class has multiple functions by same name but different parameters, it is known as Method Overloading.
Q 8 - What are Wrapper classes?
A - These are classes that allow primitive types to be accessed as objects.
B - These are classes that wraps functionality of an existing class.
Answer : A
Explaination
These are classes that allow primitive types to be accessed as objects. Example: Integer, Character, Double, Boolean etc.
Q 9 - What is runtime polymorphism?
Answer : A
Explaination
Runtime polymorphism or dynamic method dispatch is a process in which a call to an overridden method is resolved at runtime rather than at compile-time. In this process, an overridden method is called through the reference variable of a superclass.
Q 10 - What is currentThread()?
A - It is a Thread public static method used to obtain a reference to the current thread.
B - It is a thread's instance method used to get thread count.
C - It is a object's public static method used obtain a reference to the current thread.
D - It is a object's instance method used to get thread count.
Answer : A
Explaination
currentThread() is a public static method of Thread class used to obtain a reference to the current thread.
