博客
关于我
26. ForkJoin:单机版的MapReduce - 并发工具类
阅读量:386 次
发布时间:2019-03-05

本文共 2478 字,大约阅读时间需要 8 分钟。

???????ForkJoin??

??????

????????????????????????????????????????????????????????????????????????????

  • ??????????????????????????????????????
  • ??????????????????????????????
  • Fork/Join???

    Fork/Join???Java???????????????????????????????????????

    • Fork?????????fork()????????????????????
    • Join?????????join()?????????????????

    ForkJoin?????????????

  • ForkJoinPool????????????????ForkJoin???????????????????????????
  • ForkJoinTask???????????????????????????
    • fork()??????????
    • join()??????????????
  • ForkJoinTask????????

  • RecursiveAction?????????????????????????
  • RecursiveTask????????????????????????
  • ForkJoinPool????

    ForkJoinPool??????????-???????????????????????ForkJoinPool????????????????????????????????????????????????????????????????

    ForkJoinPool??????????????????????????????????

    ??MapReduce??????

    MapReduce???????????????????????????MapReduce??????????

    public class MyTest2 {    public static void main(String[] args) {        String[] fc = {            "hello world", "hello me", "hello fork", "hello join",            "fork join in world"        };        ForkJoinPool fjp = new ForkJoinPool(3);        MR mr = new MR(fc, 0, fc.length);        Map
    result = fjp.invoke(mr); result.forEach((k, v) -> System.out.println(k + ":" + v)); } static class MR extends RecursiveTask
    > { private String[] fc; private int start, end; MR(String[] fc, int fr, int to) { this.fc = fc; this.start = fr; this.end = to; } @Override protected Map
    compute() { if (end - start == 1) { return calc(fc[start]); } else { int mid = (start + end) / 2; MR mr1 = new MR(fc, start, mid); mr1.fork(); MR mr2 = new MR(fc, mid, end); return merge(mr2.compute(), mr1.join()); } } private Map
    merge(Map
    r1, Map
    r2) { Map
    result = new HashMap<>(); result.putAll(r1); r2.forEach((k, v) -> { Long c = result.get(k); if (c != null) { result.put(k, c + v); } else { result.put(k, v); } }); return result; } private Map
    calc(String line) { Map
    result = new HashMap<>(); String[] words = line.split("\\s+"); for (String w : words) { Long v = result.get(w); if (v != null) { result.put(w, v + 1L); } else { result.put(w, 1L); } } return result; } }}

    ??????MR???????????????????????ForkJoin?????????????????????????????????

    转载地址:http://hihwz.baihongyu.com/

    你可能感兴趣的文章
    MySQL 查询优化:提速查询效率的13大秘籍(避免使用SELECT 、分页查询的优化、合理使用连接、子查询的优化)(上)
    查看>>
    mysql 查询,正数降序排序,负数升序排序
    查看>>
    MySQL 树形结构 根据指定节点 获取其下属的所有子节点(包含路径上的枝干节点和叶子节点)...
    查看>>
    mysql 死锁 Deadlock found when trying to get lock; try restarting transaction
    查看>>
    mysql 死锁(先delete 后insert)日志分析
    查看>>
    MySQL 死锁了,怎么办?
    查看>>
    MySQL 深度分页性能急剧下降,该如何优化?
    查看>>
    MySQL 深度分页性能急剧下降,该如何优化?
    查看>>
    MySQL 添加列,修改列,删除列
    查看>>
    mysql 添加索引
    查看>>
    MySQL 添加索引,删除索引及其用法
    查看>>
    MySQL 用 limit 为什么会影响性能?
    查看>>
    MySQL 用 limit 为什么会影响性能?有什么优化方案?
    查看>>
    MySQL 用户权限管理:授权、撤销、密码更新和用户删除(图文解析)
    查看>>
    mysql 用户管理和权限设置
    查看>>
    MySQL 的 varchar 水真的太深了!
    查看>>
    mysql 的GROUP_CONCAT函数的使用(group_by 如何显示分组之前的数据)
    查看>>
    MySQL 的instr函数
    查看>>
    MySQL 的mysql_secure_installation安全脚本执行过程介绍
    查看>>
    MySQL 的Rename Table语句
    查看>>