详解JAVA8 函数式接口

@FunctionalInterface
public interface Consumer<T> {

  void accept(T t);
  
  default Consumer<T> andThen(Consumer<? super T> after) {
    Objects.requireNonNull(after);
    return (T t) -> { accept(t); after.accept(t); };
  }
}

public void handlerConsumer(Integer number, Consumer<Integer> consumer){
  consumer.accept(number);
}

@Test
public void test1(){
  this.handlerConsumer(10000, (i) -> System.out.println(i));
}

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

public List<Integer> getNumberList(int num, Supplier<Integer> supplier){
  List<Integer> list = new ArrayList<>();
  for(int i = 0; i < num; i++){
    list.add(supplier.get())
  }
  return list;
}

@Test
public void test2(){
  List<Integer> numberList = this.getNumberList(10, () -> new Random().nextInt(100));
  numberList.stream().forEach(System.out::println);
}

@FunctionalInterface
public interface Function<T, R> {
  
  R apply(T t);
  
  default <V> Function<V, R> compose(Function<? super V, ? extends T> before) {
    Objects.requireNonNull(before);
    return (V v) -> apply(before.apply(v));
  }

  default <V> Function<T, V> andThen(Function<? super R, ? extends V> after) {
    Objects.requireNonNull(after);
    return (T t) -> after.apply(apply(t));
  }

  static <T> Function<T, T> identity() {
    return t -> t;
  }
}

public String handlerString(String str, Function<String, String> func){
  return func.apply(str);
}

@Test
public void test3(){
  String str = this.handlerString("binghe", (s) -> s.toUpperCase());
  System.out.println(str);
}

@FunctionalInterface
public interface Predicate<T> {

  boolean test(T t);

  default Predicate<T> and(Predicate<? super T> other) {
    Objects.requireNonNull(other);
    return (t) -> test(t) && other.test(t);
  }

  default Predicate<T> negate() {
    return (t) -> !test(t);
  }

  default Predicate<T> or(Predicate<? super T> other) {
    Objects.requireNonNull(other);
    return (t) -> test(t) || other.test(t);
  }

  static <T> Predicate<T> isEqual(Object targetRef) {
    return (null == targetRef)
        ? Objects::isNull
        : object -> targetRef.equals(object);
  }
}

public List<String> filterString(List<String> list, Predicate<String> predicate){
  List<String> strList = new ArrayList<>();
  for(String str : list){
    if(predicate.test(str)){
      strList.add(str);
    }
  }
  return strList;
}

@Test
public void test4(){
  List<String> list = Arrays.asList("Hello", "Lambda", "binghe", "lyz", "World");
  List<String> strList = this.filterString(list, (s) -> s.length() >= 5);
  strList.stream().forEach(System.out::println);
}