Use Of This Operator Program in Java

public class UseOfThisOperator{
    public static void main(String[] args){
        Rectangle rectangle=new Rectangle();
        rectangle.show(5, 6);
        int area = rectangle.calculate();
        System.out.println("The area of a Rectangle is:  " + area);
    }
}

class Rectangle{
    int length, breadth;
    void show(int length, int breadth){
        this.length = length;
        this.breadth = breadth;
    }

    int calculate(){
        return(length * breadth);
    }
}