what is class and object and different ways to create object in java with example
We’re going to cover three interview questions in this session.
1. what is class in java
2. What is object in java
3. what are the different ways to create object in java
what is class in java
In Java, a class is a blueprint or a template for creating objects. It defines a data structure along with methods that operate on the data. Objects are instances of classes, and they encapsulate data and behavior. Each object created from a class can have its own unique data, but it follows the structure and behavior defined by the class.
Let’s consider a real-life example to illustrate the concept of a class in Java:
Now, you can create instances of the
Car class and use its methods to perform actions on individual cars:
In this example, the
Car class defines the attributes of a car (brand, model, year, price) and methods that represent actions a car can take (display information, start, accelerate, stop). The
main method in the
Main class demonstrates creating instances of the
Car class and using its methods to perform actions on specific cars.
What is object in java
In Java, an object is an instance of a class. A class serves as a blueprint or template, defining the structure and behavior of objects. When you create an object, you are creating a concrete instance of that class, with its own unique set of data (attributes) and behavior (methods).
Let’s extend the previous example with the
Car class and demonstrate how to create objects:
Now, let’s create objects (instances) of the
Car class in a
In this example,
car2 are objects of the
Car class. They are created using the
new keyword followed by the constructor of the class (
new Car(...)). Each object has its own set of attributes (brand, model, year, price) and can perform actions using the methods defined in the class.
Creating and using objects is fundamental to object-oriented programming, as it allows you to model and interact with real-world entities in your code.
What are different ways to create object in java
In Java, there are several ways to create objects, and the choice of method depends on the specific requirements of your program. Here are the main ways to create objects in Java:
1. Using the
new Keyword: The most common way to create an object is by using the
new keyword followed by the class constructor.
2. Using a Static Factory Method: Some classes provide static factory methods that create and return instances of the class. These methods are named and may include specific logic for object creation.
3. Using Object Cloning: The
clone() method is used to create a copy of an existing object. The class of the object being cloned must implement the
Note: Object cloning is considered somewhat complex and is not commonly used.
4. Using Deserialization: Objects can be created by deserializing them from a stream. This involves converting an object from its byte-stream representation back into an object.
Note: Deserialization involves reading objects from a file or network, and it requires the class to implement the
These are the common ways to create objects in Java. The most frequently used method is using the
new keyword and the class constructor. The other methods are used in specific scenarios or for specific design patterns.