详解Java多线程处理List数据

实例1：

解决问题：如何让n个线程顺序遍历含有n个元素的list集合

import java.util.arraylist;
import java.util.list;
import org.apache.commons.lang3.arrayutils;

public class test_4 {
/**
* 多线程处理list
*
* @param data 数据list
* @param threadnum 线程数
*/
public synchronized void handlelist(list<string> data, int threadnum) {
int length = data.size();
int tl = length % threadnum == 0 ? length / threadnum : (length
/ threadnum + 1);

for (int i = 0; i < threadnum; i++) {
int end = (i + 1) * tl;
handlethread thread = new handlethread("线程[" + (i + 1) + "] ", data, i * tl, end > length ? length : end);
thread.start();
}
}

class handlethread extends thread {
private string threadname;
private list<string> data;
private int start;
private int end;

public handlethread(string threadname, list<string> data, int start, int end) {
this.threadname = threadname;
this.data = data;
this.start = start;
this.end = end;
}

public void run() {
list<string> sublist = data.sublist(start, end)/*.add("^&*")*/;
system.out.println(threadname+"处理了"+sublist.size()+"条！");
}

}

public static void main(string[] args) {
test_4 test = new test_4();
// 准备数据
list<string> data = new arraylist<string>();
for (int i = 0; i < 6666; i++) {
data.add("item" + i);
}
test.handlelist(data, 5);
system.out.println(arrayutils.tostring(data));
}
}

实例2：

list多线程并发读取读取现有的list对象

//测试读取list的线程类，大概34秒
package com.thread.list;
 
import java.util.arraylist;
import java.util.hashmap;
import java.util.list;
import java.util.map;
 
public class main {
  
  public static void main(string[] args) {
    
    list<string> list = new arraylist<string>();
    map<long,integer> map = new hashmap<long,integer>();

    for(int i = 0;i<1000;i++){
      list.add(""+i);
    }
    
    int pcount = runtime.getruntime().availableprocessors();    
    long start = system.currenttimemillis();    
    
    for(int i=0;i<pcount;i++){
      
      thread t = new mythread1(list,map);
      map.put(t.getid(),integer.valueof(i));
      t.start();
      try {
        t.join();
      } catch (interruptedexception e) {       
        e.printstacktrace();
      }      
      // system.out.println(list.get(i));
    }    
    system.out.println("----"+(system.currenttimemillis() - start));
  }  
}

//线程类
package com.thread.list;
 
import java.util.list;
import java.util.map;
 
public class mythread1 extends thread {
 
  private list<string> list;
  private map<long,integer> map;
  
  public mythread1(list<string> list,map<long,integer> map){
    this.list = list;
    this.map = map;
  }
  
  @override
  public void run() {
    
    int pcount = runtime.getruntime().availableprocessors();
    int i = map.get(thread.currentthread().getid());
    
    for(;i<list.size();i+=pcount){
      system.out.println(list.get(i));
    }       
  }  
}

实例3：

多线程分段处理list集合

场景:大数据list集合,需要对list集合中的数据同标准库中数据进行对比,生成新增,更新,取消数据
解决方案:

1. list集合分段,
2. 动态创建线程池newfixedthreadpool
3. 将对比操作在多线程中实现

public static void main(string[] args) throws exception {

    // 开始时间
    long start = system.currenttimemillis();
    list<string> list = new arraylist<string>();

    for (int i = 1; i <= 3000; i++) {
      list.add(i + "");
    }
    // 每500条数据开启一条线程
    int threadsize = 500;
    // 总数据条数
    int datasize = list.size();
    // 线程数
    int threadnum = datasize / threadsize + 1;
    // 定义标记,过滤threadnum为整数
    boolean special = datasize % threadsize == 0;

    // 创建一个线程池
    executorservice exec = executors.newfixedthreadpool(threadnum);
    // 定义一个任务集合
    list<callable<integer>> tasks = new arraylist<callable<integer>>();
    callable<integer> task = null;
    list<string> cutlist = null;

    // 确定每条线程的数据
    for (int i = 0; i < threadnum; i++) {
      if (i == threadnum - 1) {
        if (special) {
          break;
        }
        cutlist = list.sublist(threadsize * i, datasize);
      } else {
        cutlist = list.sublist(threadsize * i, threadsize * (i + 1));
      }
      // system.out.println("第" + (i + 1) + "组：" + cutlist.tostring());
      final list<string> liststr = cutlist;
      task = new callable<integer>() {

        @override
        public integer call() throws exception {
          system.out.println(thread.currentthread().getname() + "线程：" + liststr);
          return 1;
        }
      };
      // 这里提交的任务容器列表和返回的future列表存在顺序对应的关系
      tasks.add(task);
    }

    list<future<integer>> results = exec.invokeall(tasks);

    for (future<integer> future : results) {
      system.out.println(future.get());
    }

    // 关闭线程池
    exec.shutdown();
    system.out.println("线程任务执行结束");
    system.err.println("执行任务消耗了 ：" + (system.currenttimemillis() - start) + "毫秒");
  }

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