OnJava8-Examples/functional/FunctionComposition.java

// functional/FunctionComposition.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
import java.util.function.*;

public class FunctionComposition {
  static Function<String, String>
    f1 = s -> {
      System.out.println(s);
      return s.replace('A', '_');
    },
    f2 = s -> s.substring(3),
    f3 = s -> s.toLowerCase(),
    f4 = f1.compose(f2).andThen(f3);
  public static void main(String[] args) {
    System.out.println(
      f4.apply("GO AFTER ALL AMBULANCES"));
  }
}
/* Output:
AFTER ALL AMBULANCES
_fter _ll _mbul_nces
*/