就像名字一样，他它只是一个消费者，他它的任务很简单，就是消费。

    Consumer的Function method是accept。

    1. /**
    2.      * Performs this operation on the given argument.
    3.      *
    4.      * @param t the input argument
    5.      */
    6. void accept(T t);

    andThen方法接受一个Consumer对值进行两次消费 ；）

    1. /**
    2.      * Returns a composed {@code Consumer} that performs, in sequence, this
    3.      * operation followed by the {@code after} operation. If performing either
    4.      * operation throws an exception, it is relayed to the caller of the
    5.      * composed operation.  If performing this operation throws an exception,
    6.      * the {@code after} operation will not be performed.
    7.      *
    8.      * @param after the operation to perform after this operation
    9.      * @return a composed {@code Consumer} that performs in sequence this
    10.      * operation followed by the {@code after} operation
    11.      * @throws NullPointerException if {@code after} is null
    12.      */
    13. default Consumer<T> andThen(Consumer<? super T> after) {
    14.     Objects.requireNonNull(after);
    15.     return (T t) -> { accept(t); after.accept(t); };
    16. }
    1. @Test
    2. public void consumerFi () {
    3.     List<String> stringList = new ArrayList<>();
    4.     Consumer<String> consumer = new Consumer<String>() {
    5.         @Override
    6.         public void accept (String o) {
    7.             stringList.add(o);
    8.         }
    9.     };
    10.     List<String> anotherStringList = Arrays.asList("str1", "str2", "str3", "str4", "str5");
    11.     anotherStringList.forEach(consumer);
    12.     stringList.forEach(System.out::println);
    13.     System.out.println(":3########################");
    15.     stringList.clear();
    16.     anotherStringList.forEach(consumer.andThen(new Consumer<String>() {
    17.         @Override
    18.         public void accept (String s) {
    19.             stringList.removeIf(new Predicate<String>() {
    20.                 @Override
    21.                 public boolean test (String s) {
    22.                     return s.equals("str3");
    23.                 }
    24.             });
    25.         }
    26.     }));
    27.     stringList.forEach(System.out::println);
    28. }

    输出：

    1. str1
    2. str2
    3. str3
    4. str4
    5. str5
    6. :3########################
    7. str1
    8. str2
    9. str4
    10. str5

    Consumer在流中的应用：

    • Stream中的peek
    • Stream中的forEach
    • Stream中的forEachOrdered

    等…

    Consumer在非流中的应用：

    • Iterator中的forEachRemaining
    • Iterable中的forEach

    等…