Java OOPS MCQ questions with answers

Practice Java OOPS MCQ questions with answers on classes, inheritance, polymorphism, abstraction, interfaces, and collections.

OOPS in Java

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Java OOPS MCQ questions with answers

In Java OOP, which option best describes a class?

Which OOP concept is mainly about hiding internal state and exposing controlled access?

Which keyword is commonly used to create an object in Java?

Which member is shared by all objects of the same class?

Which statement about a constructor in Java is correct?

Which access modifier gives the strongest data hiding inside a class?

Which OOP pillar is most directly related to showing only essential behavior?

A class keeps fields private and allows updates only through validated methods. This is mainly an example of:

Which statement about abstract classes is correct?

By default, a field declared inside a Java interface is:

Which statement about an abstract class is true?

Which statement is correct for a Java class?

Why does Java avoid multiple inheritance of classes?

What is the main use of `super()` inside a constructor?

What is the main use of `this()` inside a constructor?

Which statement about constructors in Java is correct?

Which relationship usually shows the strongest ownership and lifecycle dependency?

Which example best represents an IS-A relationship?

Which example best represents a HAS-A relationship?

Which option is the best sign of an immutable class?

Method overloading in Java is mainly resolved at:

Method overriding in Java is mainly resolved at:

Which change is required for valid method overloading?

Can a private method be overridden in a subclass?

What happens if a method is marked `final` in the parent class?

How are static methods treated in inheritance?

Which setup is required for runtime polymorphism?

For object fields with the same name in parent and child classes, access is mainly decided by:

Which return type change is allowed while overriding a method?

What is the likely result of downcasting a parent reference that does not actually point to that child type?

Which statement about upcasting is correct?

If a parent reference points to a child object and an overridden method is called, which version runs?

When overriding a method, the child method's access level must be:

Which checked exception rule is correct for method overriding?

What is the main use of `instanceof` before downcasting?

Which statement about interfaces is correct?

If a class implements two interfaces that provide the same default method, what must the class do?

A functional interface in Java must have:

What is a marker interface?

Which statement about constructors in interfaces is correct?

For objects in Java, what does `==` compare?

If a class does not override `equals()`, what behavior does it inherit?

What is the main risk of overriding `equals()` but not `hashCode()`?

Which statement must always be true for two equal objects?

Which class is the root parent of all Java classes?

Which commonly used Java class is immutable?

What kind of copy is usually created by default cloning behavior?

What is true about a non-static inner class?

What is true about a static nested class?

When is an anonymous class usually most appropriate?

Which statement about abstract classes is correct?

Modern Java interfaces may contain which kinds of methods?

What does declaring a class as `final` prevent?

What does `final` mean for a variable?

Which statement about a static variable is correct?

When is composition usually preferred over inheritance?

Which statement best explains the value of polymorphism?

If two references point to the exact same object, which statement is guaranteed?

Can an abstract class implement an interface without implementing all of its methods?

Which choice best supports loose coupling in Java OOP design?

Java OOPS MCQ questions with answers

In Java OOP, which option best describes a class?

Which OOP concept is mainly about hiding internal state and exposing controlled access?

Which keyword is commonly used to create an object in Java?

Which member is shared by all objects of the same class?

Which statement about a constructor in Java is correct?

Which access modifier gives the strongest data hiding inside a class?

Which OOP pillar is most directly related to showing only essential behavior?

A class keeps fields private and allows updates only through validated methods. This is mainly an example of:

Which statement about abstract classes is correct?

By default, a field declared inside a Java interface is:

Which statement about an abstract class is true?

Which statement is correct for a Java class?

Why does Java avoid multiple inheritance of classes?

What is the main use of `super()` inside a constructor?

What is the main use of `this()` inside a constructor?

Which statement about constructors in Java is correct?

Which relationship usually shows the strongest ownership and lifecycle dependency?

Which example best represents an IS-A relationship?