Functional

Functional.java

public interface Functional {

  void consume(String value);

  String supply();

  String operate(String value);

}

StringFunctional.java

public class StringFunctional implements Functional {

  @Override
  public void consume(String value) {
    System.out.println(value);
  }

  @Override
  public String supply() {
    return "supply some string";
  }

  @Override
  public String operate(String value) {
    return value.toUpperCase();
  }
}