Java Lambda Default Functional Interface

Java Lambda 기본 함수형 인터페이스 java.util.function 패키지에 정의되어 있음.

• • Functions

    public interface Function<T, R> {
      
      R apply(T t);
    }

• • Suppliers

    public interface Supplier<T> {
      T get();
    }

  • Consumers

    public interface Consumer<T> {
    
      void accept(T t); 
    }

  • Predicates

    public interface Predicate<T> {
    
      boolean test(T t); 
    }

  • Operators

    public interface UnaryOperator<T> extends Function<T, T> {
      static <T> UnaryOperator<T> identity() {
        return t -> t;
      }
    }
    

    public interface BinaryOperator<T> extends BiFunction<T,T,T> {
    
      public static <T> BinaryOperator<T> minBy(Comparator<? super T> comparator) {
        Objects.requireNonNull(comparator);
        return (a, b) -> comparator.compare(a, b) <= 0 ? a : b;
      }
    
      public static <T> BinaryOperator<T> maxBy(Comparator<? super T> comparator) {
        Objects.requireNonNull(comparator);
        return (a, b) -> comparator.compare(a, b) >= 0 ? a : b;
      }
    }