体会多线程的参数问题,可以用下面的代码测试,分别放开 注释1 和 注释2 部分,查看两次结果的不同之处。
注释1 部分,pageData 是一个引用对象,在其中一个线程中,引用对象的值进行的变动,它会影响到 其他的线程上。注释2部分,则根据传入的参数,构造了一个线程内临时变量。
method1 和 method2 提供了两种多线程的访问方式,并且获取多线程执行后的结果集
package com.bkc.bpmp.test;
import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
public class ExecutorServiceTest
{
public static void method2(List<Student> paramslist, Map pageData)
{
ExecutorService pool = Executors.newFixedThreadPool(30);
List<Callable<Object>> tasks = new ArrayList<Callable<Object>>();
for (Student stu : paramslist)
{
Callable c = new MyCallable(pageData, stu); // 执行任务并获取Future对象
tasks.add(c);
}
try
{
// 创建多个有返回值的任务
List<Future<Object>> list = pool.invokeAll(tasks);
// 获取所有并发任务的运行结果
for (Future f : list)
{
// 从Future对象上获取任务的返回值,并输出到控制台
String string = (String)f.get();
// System.out.println(string);
}
}
catch (Exception e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
// 关闭线程池
pool.shutdown();
}
public static void method1(List<Student> paramslist, Map pageData)
{
ExecutorService pool = Executors.newFixedThreadPool(30);
// 创建多个有返回值的任务
List<Future> list = new ArrayList<Future>();
for (Student stu : paramslist)
{
Callable c = new MyCallable(pageData, stu); // 执行任务并获取Future对象
Future f = pool.submit(c);
list.add(f);
}
// 关闭线程池
pool.shutdown();
// 获取所有并发任务的运行结果
for (Future f : list)
{
// 从Future对象上获取任务的返回值,并输出到控制台
try
{
String string = (String)f.get();
// System.out.println(string);
}
catch (Exception e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public static String formatDateTime(long timeMillis)
{
long day = timeMillis / (24 * 60 * 60 * 1000);
long hour = (timeMillis / (60 * 60 * 1000) - day * 24);
long min = ((timeMillis / (60 * 1000)) - day * 24 * 60 - hour * 60);
long s = (timeMillis / 1000 - day * 24 * 60 * 60 - hour * 60 * 60 - min * 60);
long sss = (timeMillis - day * 24 * 60 * 60 * 1000 - hour * 60 * 60 * 1000 - min * 60 * 1000 - s * 1000);
return (day > 0 ? day + "," : "") + hour + ":" + min + ":" + s + "." + sss;
}
public static void main(String[] args)
{
long a = System.currentTimeMillis();
Map pageData = new HashMap<>();
pageData.put("dTime", "Test");
List<Student> paramslist = new ArrayList<>();
for (int i = 0; i < 50; i++)
{
Student student = new Student("name" + i);
paramslist.add(student);
}
method1(paramslist, pageData);
System.out.println("======耗时:" + formatDateTime(System.currentTimeMillis() - a));
}
}
class MyCallable implements Callable<Object>
{
private Map pageData;
private Student stu;
public MyCallable(Map pageData, Student stu)
{
this.stu = stu;
this.pageData = pageData;
}
public void print(Map<String, String> map)
{
try
{
Thread.sleep(100);
}
catch (InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + "===" + map.toString());
}
@Override
public Object call()
throws Exception
{
/**
* 1
*/
// pageData.put("tag", stu.getName());
// print(pageData);
/**
* 2
*/
Map<String, String> map = new HashMap<>();
map.put("tag", stu.getName());
map.put("dTime", (String)pageData.get("dTime"));
print(map);
return stu.getName() + pageData.get("dTime").toString();
}
}
class Student
{
String name;
public Student()
{
super();
}
public Student(String name)
{
super();
this.name = name;
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
}
作者:panie
本文内容为作者辛苦整理书写,欢迎转载,但请保留文章出处