An example of IOC and DI.

Human.java

public class Human {
  private IHuman human;
  public Human(IHuman human) {
      this.human = human;
  }
  public void doSomeWork() {
    human.doWork();
  }
  public static void main(String[] args)
  {
    Human human = new Human(new Woman());
    human.doSomeWork();
  }
}

IHuman.java

public interface IHuman {
  void doWork();
}

Man.java

public class Man implements IHuman {
  public void doWork() {
    System.out.println("The man is working.");
  }
}

Woman.java

public class Woman implements IHuman {
  public void doWork() {
    System.out.println("The woman is working.");
  }
}