Circle.java

public class Circle extends Figure {
	private double radius;

	public Circle(double radius) {
		super();
		this.radius = radius;
	}

	double area() {
		return 3.14*radius*radius;
	}

	@Override
	public String toString() {
		return "Circle [radius=" + radius + "]";
	}
	
}

CLI.java

import java.util.ArrayList;
import java.util.Scanner;


public class CLI {
	static Scanner sc = new Scanner(System.in);

	public static void main(String[] args) {
		int choose;
		do{
			System.out.print("Select option:");
			choose = sc.nextInt();
			Circle[] tab1 = new Circle[0];
			Rectangle[] tab2 = new Rectangle[0];
			Integer[] tab3;
			if(choose == 1){
				Circle c = new Circle(sc.nextDouble());
				System.out.print("Area: "+c.area());
			}else if(choose == 2){
				Rectangle r = new Rectangle(sc.nextInt(), sc.nextInt());
				System.out.print("Area: "+r.area());
			}else if(choose == 3){
				System.out.print("Circle count:");
				int c = sc.nextInt();
				tab1 = new Circle[c];
				for(int i=0; i<c; i++){
					tab1[i] = new Circle(sc.nextDouble());
				}

				System.out.print("Rectangle count:");
				c = sc.nextInt();
				tab2 = new Rectangle[c];
				for(int i=0; i<c; i++){
					tab2[i] = new Rectangle(sc.nextInt(), sc.nextInt());
				}
				
			}else if(choose == 4){
				double epsilon = sc.nextDouble();
                int smaller;
				if(tab1.length > tab2.length){
                    smaller = tab1.length;
                }else{
                    smaller = tab2.length;
                }
				ArrayList<Integer> list = new ArrayList<Integer>();

				for(int i=0; i<smaller; i++){
					if(Math.sqrt(Math.pow(tab1[i].area()-tab2[i].area(), 2)) < epsilon){
						list.add(i);
					}
				}
				tab3 = list.toArray(new Integer[list.size()]);
			}else{
				System.out.print("Unknown option!");
			}
		}while(true);
	}
}

Figure.java

abstract class Figure {
abstract double area();

}

Rectangle.java

public class Rectangle extends Figure {
	private int width;
	private int height;
	public Rectangle(int width, int height) {
		super();
		this.width = width;
		this.height = height;
	}

	double area() {
		return this.width*this.height;
	}

	@Override
	public String toString() {
		return "Rectangle [width=" + width + ", height=" + height + "]";
	}

}