What is class design in Java?
Classes and Objects are basic concepts of Object Oriented Programming that revolve around real life entities. Show
Class1. Class is a set of object which shares common characteristics/ behavior and common properties/ attributes. A class
in java can contain: Eg: Javaclass Student { int id; String name; public static void main(String args[]) { Student s1=new Student(); System.out.println(s1.id); System.out.println(s1.name); } } A class is a user defined blueprint or prototype from which objects are created. It represents the set of properties or methods that are common to all objects of one type. In general, class declarations can include these components, in order:
Constructors are used for initializing new objects. Fields are variables that provide the state of the class and its objects, and methods are used to implement the behavior of the class and its
objects. ObjectIt is a basic unit of Object-Oriented Programming and represents real life entities. A typical Java program creates many objects, which as you know, interact by invoking methods. An object consists of :
Example of an object: dog Objects correspond to things found in the real world. For example, a graphics program may have objects such as “circle”, “square”, and “menu”. An online shopping system might have objects such as “shopping cart”, “customer”, and “product”. Declaring Objects (Also called instantiating a class)When an object of a class is created, the class is said to be instantiated. All the instances share the attributes and the behavior of the class. But the values of those attributes, i.e. the state are unique for each object. A single class may have any number of instances. Example: As we declare variables like (type name;). This notifies the compiler that we will use the name to refer to data whose type is type. With a primitive variable, this declaration also reserves the proper amount of memory for the variable. So for reference variable, the type must be strictly a concrete class name. In general, we can’t create objects of an abstract class or an interface. Dog tuffy;If we declare a reference variable(tuffy) like this, its value will
be undetermined(null) until an object is actually created and assigned to it. Simply declaring a reference variable does not create an object. Initializing an objectThe new operator instantiates a class by allocating memory for a new object and returning a reference to that memory. The new operator also invokes the class constructor. Javapublic class Dog { String name; String breed; int age; String color; public Dog(String name, String breed, int age, String color) { this.name = name; this.breed = breed; this.age = age; this.color = color; } public String getName() { return name; } public String getBreed() { return breed; } public int getAge() { return age; } public String getColor() { return color; } @Override public String toString() { return("Hi my name is "+ this.getName()+ ".\nMy breed,age and color are " + this.getBreed()+"," + this.getAge()+ ","+ this.getColor()); } public static void main(String[] args) { Dog tuffy = new Dog("tuffy","papillon", 5, "white"); System.out.println(tuffy.toString()); } } Output: Hi my name is tuffy. My breed,age and color are papillon,5,white
Note : All classes have at least one constructor. If a class does not explicitly declare any, the Java compiler automatically provides a no-argument constructor, also called the default constructor. This default constructor calls the class parent’s no-argument constructor (as it contains only one statement i.e super();), or the Object class constructor if the class has no other parent (as the Object class is the parent of all classes either directly or indirectly). Ways to create an object of a classThere are four ways to create objects in java. Strictly speaking there is only one way(by using new keyword), and the rest internally use new keyword.
Creating multiple objects by one type only (A good practice)
Anonymous objectsAnonymous objects are objects that are instantiated but are not stored in a reference variable.
This article is contributed by Gaurav Miglani. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to . See your article appearing on the GeeksforGeeks main page and help other Geeks. What do you mean by class design?A design class represents an abstraction of one or several classes in the system's implementation; exactly what it corresponds to depends on the implementation language. For example, in an object-oriented language such as C++, a class can correspond to a plain class.
What is class design in OOP?In object-oriented programming, a class is a blueprint for creating objects (a particular data structure), providing initial values for state (member variables or attributes), and implementations of behavior (member functions or methods).
How do you create a class design in Java?There are three ways to design classes: by composition, via inheritance, and via interface. Composition (or aggregation) is achieved by using existing class as a part of a new class. For example, the ArrayStack class includes an array of objects. Inheritance allows you to define a new class in terms of an old class.
What are the steps of class design?Create Initial Design Classes.. Identify Persistent Classes.. Define Class Visibility.. Define Operations.. Define Methods.. Define States.. Define Attributes.. Define Dependencies.. |