package com.zving.util;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * 多執行緒分段處理List集合 
 * 場景:大資料List集合,需要對List集合中的資料進行處理
 * @author clove
 *
 */
public class ThreadFun {

    
 
public static void main(String[] args) {

        List<String> list = new ArrayList<String>();

        for (int i = 1; i <= 3000; i++) {
            list.add(i + "");
        }
        // 每500條資料開啟一條執行緒
        int threadSize = 500;
        // 總資料條數
        int dataSize = list.size();
        // 執行緒數
 

        int threadNum = dataSize / threadSize + 1;
        // 定義標記,過濾threadNum為整數
        boolean special = dataSize % threadSize == 0;

        // 建立一個執行緒池
        ExecutorService exec = Executors.newFixedThreadPool(threadNum);
        // 定義一個任務集合
        List<Callable<Boolean>> tasks = new ArrayList<Callable<Boolean>>();
        Callable
 
<Boolean> task = null;
        List<String> cutList = null;

        // 確定每條執行緒的資料
        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));
            }
            final List<String> listStr = cutList;
            task = new Callable<Boolean>() {
                @Override
                public Boolean call() throws Exception {
                    if (null != listStr && listStr.size() > 0) {
                        for (String str : listStr) {
                            // 呼叫業務方法
                            downloadFile(str);
                        }
                    }
                    return true;
                }
            };
            tasks.add(task);
        }

        try {
            exec.invokeAll(tasks);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // 關閉執行緒池
        exec.shutdown();
    }

    private static void downloadFile(String str) {
        //執行多執行緒檔案下載業務邏輯
        System.out.println(str);
    }

}