Java Object Behavior and Methods
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Questions and Answers

In object-oriented programming, what is the function of a method?

  • Create a new instance of a class
  • Perform actions on the object's data (correct)
  • Declare the relationships between objects
  • Define the properties of an object

    • What is the purpose of a class in object-oriented programming?

  • To create a new object
  • To implement an abstract data type
  • To declare the relationships between objects
  • To define the template for creating objects (correct)

    • What is an abstract data type?

  • A structure that contains relationships between objects
  • A structure that contains only actions
  • A structure that contains only data
  • A structure that contains both data and actions (correct)

    • What is the difference between a class and an object?

    <p>A class is a template for creating objects</p> Signup and view all the answers

    What is an example of an object?

    <p>Car, VDU, CLOCK</p> Signup and view all the answers

    What are the components of a class?

    <p>Attributes and operations</p> Signup and view all the answers

    What is the purpose of polymorphism in object-oriented programming?

    <p>To allow objects of different classes to respond to the same method</p> Signup and view all the answers

    What is the purpose of a method in a class?

    <p>To perform actions on the object's data</p> Signup and view all the answers

    What is the difference between a class attribute and an object attribute?

    <p>A class attribute is shared by all objects, while an object attribute is specific to one object</p> Signup and view all the answers

    What is the term for creating a new instance of a class?

    <p>Object initialization</p> Signup and view all the answers

    Study Notes

    Array Initialization

    • A string array cannot be initialized with a single string value, it needs to be initialized with a size.
    • Assigning a new string value to an array does not add to the array, it replaces the existing value.

    Object Behavior: Methods

    • Instance methods exist inside each object of a class and give behavior to each object.
    • Instance methods have the same syntax as static methods, but without the static keyword.
    • Example of an instance method: public void shout() { System.out.println("HELLO THERE!"); }

    Mutator Methods

    • A mutator method is used to change the state of an object.
    • Example of a mutator method: public void setLocation(int newX, int newY) { x = newX; y = newY; }
    • Another example of a mutator method: public void translate(int dx, int dy) { x = x + dx; y = y + dy; }

    Accessor Methods

    • An accessor method is used to retrieve information from an object.
    • Example of an accessor method: public double distance(Point other) { ... }
    • Another example of an accessor method: public double distanceFromOrigin() { ... }

    Printing Objects

    • By default, Java does not know how to print objects.
    • The toString() method is used to convert an object into a string.
    • The toString() method is called implicitly when printing an object using System.out.println().

    The toString() Method

    • The toString() method is used to convert an object into a string.
    • The toString() method has a specific syntax: public String toString() { ... }
    • The toString() method is used to represent an object as a string.

    Object Initialization: Constructors

    • Constructors are used to initialize objects.
    • A constructor is a special method that has the same name as the class.
    • Constructors are used to specify the initial values of an object's fields.

    Object-Oriented Programming (OOP)

    • OOP is a programming paradigm that uses classes and objects to represent data and behavior.
    • The fundamentals of OOP are:
      • Classes and Objects
      • Encapsulation
      • Inheritance
      • Polymorphism (Overriding and Overloading)
      • Abstraction

    Classes and Objects

    • A class is a blueprint or template for creating objects.
    • An object is an instance of a class.
    • A class defines the properties and behavior of an object.

    Abstract Data Type (ADT)

    • An ADT is a structure that contains both data and the actions to be performed on that data.
    • A class is an implementation of an ADT.

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    Description

    Understanding object behavior, instance methods in Java. Learn about methods and object methods in Java programming.

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