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Ejercicio 1 builds the simplest possible abstract class hierarchy: a geometric figure. Every figure has a name and must be able to report its area, but the formula for computing that area differs completely between a circle and a rectangle. The abstract class FiguraT11 captures the common structure — the nombre field and the mostrarArea() display method — while delegating the actual calculation to each concrete subclass through the abstract method calcularArea().
Class Hierarchy
FiguraT11 (abstract)
├── CirculoT11 — area = π × radio²
└── RectanguloT11 — area = base × altura
FiguraT11 — Abstract Base Class
FiguraT11 holds a single protected field nombre and declares calcularArea() as abstract. Its concrete method mostrarArea() calls calcularArea() — this is the template method pattern: the base class orchestrates the output, but relies on the subclass to supply the numeric result.
package Taller11;
abstract class FiguraT11 {
protected String nombre;
public FiguraT11(String nombre) {
this.nombre = nombre;
}
// Método abstracto que debe ser implementado por las subclases
public abstract double calcularArea();
// Método concreto que utiliza el método abstracto
public void mostrarArea() {
System.out.println("El área de " + nombre + " es: " + calcularArea());
}
}
How the Template Method Works
When mostrarArea() is called on any FiguraT11 reference, Java dispatches calcularArea() to the runtime type of the object — never to the abstract declaration in FiguraT11. This means:
FiguraT11 defines when calcularArea() is called (inside mostrarArea()).- The concrete subclass defines what it returns.
CirculoT11 — Circle Implementation
CirculoT11 stores a radio (radius) and overrides calcularArea() using the standard circle-area formula π × r² via Math.PI.
package Taller11;
class CirculoT11 extends FiguraT11 {
private double radio;
public CirculoT11(String nombre, double radio) {
super(nombre);
this.radio = radio;
}
@Override
public double calcularArea() {
return Math.PI * radio * radio;
}
}
RectanguloT11 — Rectangle Implementation
RectanguloT11 stores base and altura and overrides calcularArea() with simple multiplication.
package Taller11;
class RectanguloT11 extends FiguraT11 {
private double base;
private double altura;
public RectanguloT11(String nombre, double base, double altura) {
super(nombre);
this.base = base;
this.altura = altura;
}
@Override
public double calcularArea() {
return base * altura;
}
}
Polymorphism with Abstract Classes
Because both concrete classes extend FiguraT11, variables of type FiguraT11 can hold either subtype. The correct calcularArea() is selected at runtime through dynamic dispatch:
package Taller11;
public class MainEjercicio1T11 {
public static void main(String[] args) {
System.out.println("--- Demostración de Clases Abstractas (Ejercicio 1) ---");
// No se puede instanciar directamente una clase abstracta:
// FiguraT11 figura = new FiguraT11("Figura Genérica"); // Esto daría un error de compilación
CirculoT11 circulo = new CirculoT11("Círculo Grande", 5.0);
RectanguloT11 rectangulo = new RectanguloT11("Rectángulo Pequeño", 4.0, 6.0);
circulo.mostrarArea();
rectangulo.mostrarArea();
System.out.println("\n--- Polimorfismo con Clases Abstractas ---");
FiguraT11 f1 = new CirculoT11("Círculo Mediano", 3.5);
FiguraT11 f2 = new RectanguloT11("Rectángulo Largo", 8.0, 2.5);
f1.mostrarArea(); // calls CirculoT11's calcularArea()
f2.mostrarArea(); // calls RectanguloT11's calcularArea()
}
}
Expected Output
--- Demostración de Clases Abstractas (Ejercicio 1) ---
El área de Círculo Grande es: 78.53981633974483
El área de Rectángulo Pequeño es: 24.0
--- Polimorfismo con Clases Abstractas ---
El área de Círculo Mediano es: 38.48451000647496
El área de Rectángulo Largo es: 20.0
Even though f1 and f2 are declared as FiguraT11, Java always calls the overriding implementation in the actual object’s class. This is dynamic (runtime) polymorphism in action — the same method call produces different results based solely on the runtime type.
Compile & Run
# From the project root
javac Taller11/Figura.java Taller11/Circulo.java Taller11/Rectangulo.java Taller11/MainEjercicio1T11.java
# Run
java Taller11.MainEjercicio1T11