Sample usage of reduce operation in Java Stream API with three parameters

StreamReduceFourthSample.java

  String carModels = cars.parallelStream()
       .map(c1 -> c1.getModel())
       .distinct()
       .reduce("Renault", 
                (s1, s2) -> { 
                      System.out.printf("s1: %s and s2: %s \n", s1, s2);
                      return s1 + "|" + s2; 
                }, 
                (com1, com2) -> {
                      System.out.printf("com1: %s and com2: %s \n", com1, com2);
                      int indexOf = com2.indexOf('|');
                      if(indexOf > 0){
                           return com1 + com2.substring(indexOf); //remove 'Renault|' for the second strint
                      }
                      return com1;
                 }
         );
  System.out.println(carModels);
  // s1: Renault and s2: BMW 
  // s1: Renault and s2: Ford 
  // s1: Renault and s2: Toyota 
  // com1: Renault|Ford and com2: Renault|Toyota 
  // com1: Renault|BMW and com2: Renault|Ford|Toyota 
  // com1: Renault|BMW|Ford|Toyota and com2: Renault 
  // Renault|BMW|Ford|Toyota