diff --git b/EjemploInterface.java a/EjemploInterface.java
new file mode 100644
index 0000000..889aed6
--- /dev/null
+++ a/EjemploInterface.java
@@ -0,0 +1,147 @@
+public class EjemploInterface {
+    public static void main(String[] args) {
+        Forma cir = new Circulo( "Rojo",5.f);
+        Forma cuad = new Rectangulo("Amarillo", 5.f, 3.f);
+        Cartel cartel1 = new Cartel(cir, "Peligro");
+        Cartel cartel2 = new Cartel(cuad, "Atencion");
+        System.out.println(cartel1.cuadraTexto());
+        System.out.println(cartel2.cuadraTexto());
+
+    }
+}
+
+interface Forma{
+
+    public String getColor();
+
+    public void setColor(String color);
+
+    public float getPerimetro();
+
+    public float getArea();
+
+    public float getLongitud();
+}
+
+
+class Cartel{
+
+    private Forma forma;
+    private String texto;
+
+    public Cartel(Forma forma, String texto) {
+        this.forma = forma;
+        this.texto = texto;
+    }
+
+    public Forma getForma(){
+        return this.forma;
+    }
+
+    public void setForma(Forma forma){
+        this.forma = forma;
+    }
+
+    public String getTexto(){
+        return this.texto;
+    }
+
+    public void setTexto(String texto){
+        this.texto = texto;
+    }
+
+    public boolean cuadraTexto(){
+        return this.texto.length() < this.forma.getLongitud();
+    }
+}
+
+class Circulo implements Forma{
+    private String color;
+    private float radio;
+
+    public Circulo(String color, float radio) {
+        this.color = color;
+        this.radio = radio;
+    }
+
+    @Override
+    public String getColor() {
+        
+        return color;
+    }
+
+    @Override
+    public void setColor(String color) {
+        this.color = color;
+        
+    }
+
+    @Override
+    public float getPerimetro() {
+        
+        return (float)Math.PI*2*radio;
+    }
+
+    @Override
+    public float getArea() {
+        
+        return (float)Math.PI*radio*radio;
+    }
+
+    @Override
+    public float getLongitud() {
+        // TODO Auto-generated method stub
+        return 2*radio;
+    }
+    
+} 
+
+class Rectangulo implements Forma{
+    private String color;
+    private float largo;
+    private float ancho;
+
+    public Rectangulo(String color, float largo, float ancho) {
+        this.color = color;
+        this.largo = largo;
+        this.ancho = ancho;
+    }
+
+    @Override
+    public String getColor() {
+        
+        return color;
+    }
+
+    @Override
+    public void setColor(String color) {
+        this.color = color;
+        
+    }
+
+    @Override
+    public float getPerimetro() {
+        
+        return 2*(largo+ancho);
+    }
+
+    @Override
+    public float getArea() {
+        
+        return largo*ancho;
+    }
+
+    public float getAncho() {
+        return ancho;
+    }
+    public float getLongitud() {
+        return largo;
+    }
+    public void setAncho(float ancho) {
+        this.ancho = ancho;
+    }
+    public void setLongitud(float largo) {
+        this.largo = largo;
+    }
+    
+} 
\ No newline at end of file