# Superclass & Subclass in Java

Paul Tomoiu

●

Examples,

Concepts,

Classes

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Published 2022-12-23

# Superclass & Subclass in Java - Theory

In Java OPP (Object-Oriented Programming) we speak about 4 main concepts:

Info

extends is the keyword used to inherit the attributes and the methods of a class.

The pattern is like this:

class SuperClass {
//Some code here
  
}

class SubClass extends SuperClass {
//Some code here
  
}

The class which inherits the properties of other is known as subclass (child class) and the class whose properties are inherited is known as superclass (parent class).

# Superclass & Subclass in Java - Example

Here is an example of Java inheritance:

Shape.java
public class Shape {

    public void drawShape1(){
        System.out.println("Hello from drawShape1 !");
    };
    
    public void drawShape2(){
        System.out.println("Hello from drawShape2 !");
    };
}

Triangle.java
public class Triangle extends Shape {

    void eraseShape() {
        System.out.println("Hello from Triangle/eraseShape !");
    }
    
    // method OVERRIDING
    @Override
    public void drawShape2() {
        System.out.println("Hello from Triangle/eraseShape2 !");
    }
    
    // method OVERLOADING 
    public void drawShape2(String par1) {
        System.out.println("Hello "+par1+" from eraseShape2 !");
    }
}

Info

When a class inherits the methods of another class it can override & overload these methods.

MainApp.java
public class MainApp {

    public static void main(String [] args) {
        Triangle triangle = new Triangle();
        triangle.drawShape2();
        triangle.drawShape2("Paris");
    }
}

As you can see in the Triangle class you can use drawShape() method defined in the Shape class. The same thing happens with the attributes (variables) of the class.