Object Oriented Programming Lecture 6: Interfaces
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Questions and Answers

What is the default access modifier for interface fields in Java?

  • protected
  • private
  • public (correct)
  • static

    • Which keyword is used to implement an interface in Java?

  • use
  • inherit
  • implements (correct)
  • extend

    • What is a benefit of default methods in Java interfaces?

  • They can be declared via the abstract keyword
  • Implementing classes may or may not override them (correct)
  • They are implicitly private
  • They cannot have a body

    • Which method is added to the Vehicle interface in the updated version?

    <p>slowDown()</p> Signup and view all the answers

    Which access modifiers are not allowed for fields in a Java interface?

    <p>private and protected</p> Signup and view all the answers

    What is the main purpose of an interface in Java?

    <p>To impose a contract between a class and the outside world</p> Signup and view all the answers

    Can an interface have concrete (non-abstract) methods?

    <p>No, interfaces can only have abstract methods</p> Signup and view all the answers

    How many interfaces can a class implement in Java?

    <p>A class can implement multiple interfaces</p> Signup and view all the answers

    What is the main difference between an interface and an abstract class in Java?

    <p>An interface can have fields and methods, while an abstract class cannot</p> Signup and view all the answers

    If a class implements an interface in Java, what is the requirement?

    <p>The class must override all of the interface methods</p> Signup and view all the answers

    Study Notes

    Interface Fields in Java

    • The default access modifier for interface fields in Java is public static final.
    • The implements keyword is used to implement an interface in Java.

    Benefits of Default Methods

    • A benefit of default methods in Java interfaces is that they allow developers to add new functionality to interfaces without breaking existing implementations.

    Updating Interfaces

    • The printDetails method is added to the Vehicle interface in the updated version.

    Interface Field Access Modifiers

    • The private and protected access modifiers are not allowed for fields in a Java interface.

    Purpose of Interfaces

    • The main purpose of an interface in Java is to define a contract that must be implemented by any class that implements it.

    Interface Methods

    • An interface can have concrete (non-abstract) methods, known as default methods, which provide a default implementation that can be overridden by implementing classes.

    Implementing Multiple Interfaces

    • A class can implement multiple interfaces in Java.

    Interfaces vs Abstract Classes

    • The main difference between an interface and an abstract class in Java is that an interface cannot have instance variables, while an abstract class can.

    Implementing Interfaces

    • If a class implements an interface in Java, it is required to provide an implementation for all the abstract methods declared in the interface.

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    Description

    Learn the concepts of interfaces in Object Oriented Programming (OOP) including how to implement and define interfaces, interface data members, default methods, usages of interfaces like Comparable and Comparator, and the differences between interfaces and abstract classes.

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