Polymorphism

public class Shape {
    public String name() { return "Shape"; }
}
public class Circle extends Shape {
    public String name() { return "Circle"; }
}
public class Square extends Shape {
    public String name() { return "Square"; }
}
// Usage:
ArrayList<Shape> list = new ArrayList<Shape>();
list.add(new Circle());
list.add(new Square());
list.add(new Shape());
String s = "";
for (int i = 0; i < list.size(); i++) {
    s += list.get(i).name();
}
System.out.print(s);

• A

  ShapeShapeShape

• B

  CircleSquare

• C

  CircleSquareShape

  check_circle
• D

  Compile error