Java Object Behavior and Methods

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.