Spliterator介紹

一、Spliterator　　　　

Spliterator<T> trySplit();
trySplit接口就相當於我們之前寫的AccumulatorRecursiveTask類裏面的分割任務，如果滿足條件就繼續往下分，返回一個新的spliterator出來。
Spliterator就相當於我們寫的fork join邏輯，Stream就是使用Spliterator來實現fork join的功能，來實現多任務切分的。

代碼例子：

  1 package com.cy.java8;
  2 
  3 import java.util.Objects;
  4 import java.util.Optional;
  5 import java.util.Spliterator;
  6 import java.util.function.Consumer;
  7 import java.util.stream.IntStream;
  8 import java.util.stream.Stream;
  9 import java.util.stream.StreamSupport;
 10 
 11 public class SpliteratorInAction {
 12     private static String text =
 13                     "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Etiam in lacinia massa, quis eleifend dui. Sed in molestie ex.\n" +
 14                     "\n" +
 15                     "Integer dictum, erat ut interdum viverra, erat dui suscipit eros, eget vestibulum mi massa ut sem. Donec ultrices.\n" +
 16                     "\n" +
 17                     "Quisque lacinia non enim venenatis efficitur. Duis luctus at ex at ullamcorper. Fusce maximus sapien a scelerisque.\n" +
 18                     "\n" +
 19                     "Morbi eu congue ipsum, ac lobortis nulla. Proin cursus tortor lectus, nec luctus lectus ornare a. Mauris gravida nisl.";
 20 
 21     public static void main(String[] args) {
 22         IntStream intStream = IntStream.rangeClosed(0, 10);
 23         Spliterator.OfInt spliterator = intStream.spliterator();
 24         spliterator.forEachRemaining((Consumer<Integer>) integer -> System.out.println(integer));
 25 
 26         MySpliteratorText mySpliteratorText = new MySpliteratorText(text);
 27         Optional.ofNullable(mySpliteratorText.stream().count())
 28                 .ifPresent(System.out::println);
 29         mySpliteratorText.stream().filter(s -> !s.equals("")).forEach(System.out::println);
 30 
 31         Optional.ofNullable(mySpliteratorText.parallelStream().count())
 32                 .ifPresent(System.out::println);
 33         mySpliteratorText.parallelStream().filter(s -> !s.equals("")).forEach(System.out::println);
 34     }
 35 
 36     /**
 37      * 自定義實現Spliterator接口
 38      */
 39     public static class MySpliteratorText {
 40         private final String[] data;
 41 
 42         public MySpliteratorText(String text) {
 43             Objects.requireNonNull(text, "the parameter can not be null");
 44             this.data = text.split("\n");
 45         }
 46 
 47         public Stream<String> stream() {
 48             return StreamSupport.stream(new MySpliterator(), false);
 49         }
 50 
 51         public Stream<String> parallelStream() {
 52             return StreamSupport.stream(new MySpliterator(), true);
 53         }
 54 
 55         private class MySpliterator implements Spliterator<String> {
 56             private int start, end;
 57 
 58             public MySpliterator() {
 59                 this.start = 0;
 60                 this.end = data.length - 1;
 61             }
 62 
 63             public MySpliterator(int start, int end) {
 64                 this.start = start;
 65                 this.end = end;
 66             }
 67 
 68             @Override
 69             public boolean tryAdvance(Consumer<? super String> action) {
 70                 if (start <= end) {
 71                     action.accept(data[start++]);
 72                     return true;
 73                 }
 74                 return false;
 75             }
 76 
 77             @Override
 78             public Spliterator<String> trySplit() {
 79                 int mid = (end - start) / 2;
 80                 if (mid <= 1) {
 81                     return null;
 82                 }
 83 
 84                 int left = start;
 85                 int right = start + mid;
 86                 start = start + mid + 1;
 87                 return new MySpliterator(left, right);
 88             }
 89 
 90             @Override
 91             public long estimateSize() {
 92                 return end - start;
 93             }
 94 
 95             @Override
 96             public long getExactSizeIfKnown() {
 97                 return estimateSize();
 98             }
 99 
100             @Override
101             public int characteristics() {
102                 return IMMUTABLE | SIZED | SUBSIZED;
103             }
104         }
105     }
106 }

console打印：

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Lorem ipsum dolor sit amet, consectetur adipiscing elit. Etiam in lacinia massa, quis eleifend dui. Sed in molestie ex.
Integer dictum, erat ut interdum viverra, erat dui suscipit eros, eget vestibulum mi massa ut sem. Donec ultrices.
Quisque lacinia non enim venenatis efficitur. Duis luctus at ex at ullamcorper. Fusce maximus sapien a scelerisque.
Morbi eu congue ipsum, ac lobortis nulla. Proin cursus tortor lectus, nec luctus lectus ornare a. Mauris gravida nisl.
7
Quisque lacinia non enim venenatis efficitur. Duis luctus at ex at ullamcorper. Fusce maximus sapien a scelerisque.
Morbi eu congue ipsum, ac lobortis nulla. Proin cursus tortor lectus, nec luctus lectus ornare a. Mauris gravida nisl.
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Etiam in lacinia massa, quis eleifend dui. Sed in molestie ex.
Integer dictum, erat ut interdum viverra, erat dui suscipit eros, eget vestibulum mi massa ut sem. Donec ultrices.

　　

 

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