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:
- List集合分段,
-
动态创建线程池
newFixedThreadPool - 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");
}