Component.java

interface Component {
  public void update(int delta);
  public void render();
}

Entity.java

import java.util.*;

class Entity {
  private List<Component> components = new ArrayList<Component>();

  public void addComponent(Component c) {
    components.add(c);
  }

  public void update(int delta) {
    for (Component c : components) {
      c.update();
    }
  }
  
  public void render() {
    for (Component c : components) {
      c.render();
    }
  }
}