24 OOP & Classes questions from the Java bank, written for Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd.
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A.the OOP principle of hiding internal state behind private fields and exposing it only through controlled accessor methods
B.the ability for a single method call to dispatch to different implementations at runtime depending on the actual object type
C.a blueprint that defines the fields and methods from which objects are instantiated
D.the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword
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2. Which term means: "a blueprint that defines the fields and methods from which objects are instantiated"?
Junior
A.Interface
B.Class
C.Polymorphism
D.Default method
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3. Which statement is correct?
Junior
A.Class — an interface method with a body, introduced in Java 8, that lets new behavior be added to an interface without breaking existing implementers
B.Class — the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword
C.Class — a blueprint that defines the fields and methods from which objects are instantiated
D.Class — a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance
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4. What is Inheritance?
Junior
A.the ability for a single method call to dispatch to different implementations at runtime depending on the actual object type
B.the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword
C.defining multiple methods with the same name but different parameter lists, resolved by the compiler at compile time
D.a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance
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5. Which term means: "the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword"?
Junior
A.Inheritance
B.Interface
C.Encapsulation
D.Class
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6. Which statement is correct?
Junior
A.Inheritance — a class declared abstract that cannot be instantiated and may contain unimplemented methods, allowing partial implementation and state for subclasses
B.Inheritance — the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword
C.Inheritance — the ability for a single method call to dispatch to different implementations at runtime depending on the actual object type
D.Inheritance — a blueprint that defines the fields and methods from which objects are instantiated
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7. What is Polymorphism?
Mid
A.a class declared abstract that cannot be instantiated and may contain unimplemented methods, allowing partial implementation and state for subclasses
B.the ability for a single method call to dispatch to different implementations at runtime depending on the actual object type
C.an interface method with a body, introduced in Java 8, that lets new behavior be added to an interface without breaking existing implementers
D.the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword
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8. Which term means: "the ability for a single method call to dispatch to different implementations at runtime depending on the actual object type"?
Mid
A.Default method
B.Class
C.Polymorphism
D.Encapsulation
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9. Which statement is correct?
Mid
A.Polymorphism — a class declared abstract that cannot be instantiated and may contain unimplemented methods, allowing partial implementation and state for subclasses
B.Polymorphism — the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword
C.Polymorphism — a blueprint that defines the fields and methods from which objects are instantiated
D.Polymorphism — the ability for a single method call to dispatch to different implementations at runtime depending on the actual object type
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10. What is Abstract class?
Mid
A.a blueprint that defines the fields and methods from which objects are instantiated
B.the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword
C.a class declared abstract that cannot be instantiated and may contain unimplemented methods, allowing partial implementation and state for subclasses
D.an interface method with a body, introduced in Java 8, that lets new behavior be added to an interface without breaking existing implementers
Answer + AI explanation with Pro
11. Which term means: "a class declared abstract that cannot be instantiated and may contain unimplemented methods, allowing partial implementation and state for subclasses"?
Mid
A.Inheritance
B.Default method
C.Abstract class
D.Interface
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12. Which statement is correct?
Mid
A.Abstract class — a class declared abstract that cannot be instantiated and may contain unimplemented methods, allowing partial implementation and state for subclasses
B.Abstract class — the OOP principle of hiding internal state behind private fields and exposing it only through controlled accessor methods
C.Abstract class — the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword
D.Abstract class — a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance
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13. What is Interface?
Mid
A.a class declared abstract that cannot be instantiated and may contain unimplemented methods, allowing partial implementation and state for subclasses
B.a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance
C.an interface method with a body, introduced in Java 8, that lets new behavior be added to an interface without breaking existing implementers
D.a blueprint that defines the fields and methods from which objects are instantiated
Answer + AI explanation with Pro
14. Which term means: "a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance"?
Mid
A.Inheritance
B.Abstract class
C.Encapsulation
D.Interface
Answer + AI explanation with Pro
15. Which statement is correct?
Mid
A.Interface — defining multiple methods with the same name but different parameter lists, resolved by the compiler at compile time
B.Interface — the ability for a single method call to dispatch to different implementations at runtime depending on the actual object type
C.Interface — a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance
D.Interface — an interface method with a body, introduced in Java 8, that lets new behavior be added to an interface without breaking existing implementers
Answer + AI explanation with Pro
16. What is Default method?
Senior
A.defining multiple methods with the same name but different parameter lists, resolved by the compiler at compile time
B.an interface method with a body, introduced in Java 8, that lets new behavior be added to an interface without breaking existing implementers
C.the OOP principle of hiding internal state behind private fields and exposing it only through controlled accessor methods
D.the ability for a single method call to dispatch to different implementations at runtime depending on the actual object type
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17. Which term means: "an interface method with a body, introduced in Java 8, that lets new behavior be added to an interface without breaking existing implementers"?
Senior
A.Polymorphism
B.Inheritance
C.Default method
D.Class
Answer + AI explanation with Pro
18. Which statement is correct?
Senior
A.Default method — the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword
B.Default method — a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance
C.Default method — a blueprint that defines the fields and methods from which objects are instantiated
D.Default method — an interface method with a body, introduced in Java 8, that lets new behavior be added to an interface without breaking existing implementers
Answer + AI explanation with Pro
19. What is Encapsulation?
Mid
A.defining multiple methods with the same name but different parameter lists, resolved by the compiler at compile time
B.the OOP principle of hiding internal state behind private fields and exposing it only through controlled accessor methods
C.a class declared abstract that cannot be instantiated and may contain unimplemented methods, allowing partial implementation and state for subclasses
D.a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance
Answer + AI explanation with Pro
20. Which term means: "the OOP principle of hiding internal state behind private fields and exposing it only through controlled accessor methods"?
Mid
A.Inheritance
B.Encapsulation
C.Polymorphism
D.Default method
Answer + AI explanation with Pro
21. Which statement is correct?
Mid
A.Encapsulation — a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance
B.Encapsulation — the OOP principle of hiding internal state behind private fields and exposing it only through controlled accessor methods
C.Encapsulation — a class declared abstract that cannot be instantiated and may contain unimplemented methods, allowing partial implementation and state for subclasses
D.Encapsulation — a blueprint that defines the fields and methods from which objects are instantiated
Answer + AI explanation with Pro
22. What is Method overloading?
Mid
A.an interface method with a body, introduced in Java 8, that lets new behavior be added to an interface without breaking existing implementers
B.defining multiple methods with the same name but different parameter lists, resolved by the compiler at compile time
C.the OOP principle of hiding internal state behind private fields and exposing it only through controlled accessor methods
D.a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance
Answer + AI explanation with Pro
23. Which term means: "defining multiple methods with the same name but different parameter lists, resolved by the compiler at compile time"?
Mid
A.Interface
B.Default method
C.Method overloading
D.Abstract class
Answer + AI explanation with Pro
24. Which statement is correct?
Mid
A.Method overloading — a blueprint that defines the fields and methods from which objects are instantiated
B.Method overloading — a fully abstract contract of method signatures that a class implements, supporting multiple inheritance of type since Java allows only single class inheritance
C.Method overloading — defining multiple methods with the same name but different parameter lists, resolved by the compiler at compile time
D.Method overloading — the mechanism by which a subclass acquires the fields and methods of a superclass using the extends keyword
Answer + AI explanation with Pro
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