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What is Instance In Programming


By onjsdev

Dec 29th, 2023

In programming, the term instance has several different meanings depending on the specific context. Here are some of the most common usages.

Instance in Object-Oriented Programming (OOP)

In OOP, an instance refers to a specific occurrence or realization of a class. On other hand a class is a blueprint or template for creating instances. They are used to define the properties (attributes) and behaviors (methods) of instances. So an instance is created based on a class.

Here is an example from Java

// Example in Java
public class Car {
    String brand;
    String model;

    // Constructor
    public Car(String brand, String model) {
        this.brand = brand;
        this.model = model;
    }
}

// Creating an instance
Car myCar = new Car("Toyota", "Camry");

We can also talk about an analogy here. The "Car" class is like a blueprint for building cars, specifying features such as brand, model, and engine. Creating a specific car, like a red Honda Civic, is an instance of the "Car" class.

Instance in other contexts

Outside of OOP, the term instance can have broader meanings depending on the programming language or technology being used.

Here are some examples:

  • Database instance: refers to a specific copy of a database schema and data running on a server.
  • Process instance: refers to a single execution of a program in a system.
  • Function instance: refers to a specific invocation of a function with its own set of arguments and execution context.
  • Variable instance: refers to a specific memory location holding a value for a variable.

Conclusion

It's important to note that the specific meaning of instance always depends on the context. In this article, we have covered some of them.

Thank you for reading.