小弟今天看了篇关于多线程的文章, 按照文中的例子编写测试运行了下程序,对运行的结果有点疑问,
请各位说说看,为什么在
“创建第【4】个线程!”之后 “线程[3] is running, 线程总数count=1 ” 这里 总数count怎么还等于1呢?前面count的最大值已经累加到等于3了!! count 的值似乎没有什么规律啊,我觉得应该是递增的才对啊 -------------------运行结果如下---------------------------
D:\java\test\thread>java MyThread
创建第【1】个线程!
创建第【2】个线程!
线程[1] is running, 线程总数count=1
创建第【3】个线程!
线程[1] is running, 线程总数count=2
线程[2] is running, 线程总数count=1
创建第【4】个线程!
线程[1] is running, 线程总数count=3
线程[3] is running, 线程总数count=1
线程[2] is running, 线程总数count=2
创建第【5】个线程!
线程[1] is running, 线程总数count=4
线程[4] is running, 线程总数count=1
线程[3] is running, 线程总数count=2
线程[2] is running, 线程总数count=3
线程[1] is running, 线程总数count=5
线程[5] is running, 线程总数count=1
线程[4] is running, 线程总数count=2
线程[3] is running, 线程总数count=3
线程[2] is running, 线程总数count=4
线程[5] is running, 线程总数count=2
线程[4] is running, 线程总数count=3
线程[3] is running, 线程总数count=4
线程[2] is running, 线程总数count=5
线程[5] is running, 线程总数count=3
线程[4] is running, 线程总数count=4
线程[3] is running, 线程总数count=5
线程[5] is running, 线程总数count=4
线程[4] is running, 线程总数count=5
线程[5] is running, 线程总数count=5
--------------------------------------------------------------------------原程序如下----------------------------import java.lang.Thread;
public class MyThread extends Thread
{
int num, count=1; public MyThread(int i){
System.out.println(" 创建第【"+i+"】个线程!");
num = i ;
} public void run(){
while(true){
System.out.println("线程["+num+"] is running, 线程总数count="+count);
if(++count==6)
return;
}
} public static void main(String[] args)
{
for(int j=0; j<5; j++){
new MyThread(j+1).start();
}
}
}
请各位说说看,为什么在
“创建第【4】个线程!”之后 “线程[3] is running, 线程总数count=1 ” 这里 总数count怎么还等于1呢?前面count的最大值已经累加到等于3了!! count 的值似乎没有什么规律啊,我觉得应该是递增的才对啊 -------------------运行结果如下---------------------------
D:\java\test\thread>java MyThread
创建第【1】个线程!
创建第【2】个线程!
线程[1] is running, 线程总数count=1
创建第【3】个线程!
线程[1] is running, 线程总数count=2
线程[2] is running, 线程总数count=1
创建第【4】个线程!
线程[1] is running, 线程总数count=3
线程[3] is running, 线程总数count=1
线程[2] is running, 线程总数count=2
创建第【5】个线程!
线程[1] is running, 线程总数count=4
线程[4] is running, 线程总数count=1
线程[3] is running, 线程总数count=2
线程[2] is running, 线程总数count=3
线程[1] is running, 线程总数count=5
线程[5] is running, 线程总数count=1
线程[4] is running, 线程总数count=2
线程[3] is running, 线程总数count=3
线程[2] is running, 线程总数count=4
线程[5] is running, 线程总数count=2
线程[4] is running, 线程总数count=3
线程[3] is running, 线程总数count=4
线程[2] is running, 线程总数count=5
线程[5] is running, 线程总数count=3
线程[4] is running, 线程总数count=4
线程[3] is running, 线程总数count=5
线程[5] is running, 线程总数count=4
线程[4] is running, 线程总数count=5
线程[5] is running, 线程总数count=5
--------------------------------------------------------------------------原程序如下----------------------------import java.lang.Thread;
public class MyThread extends Thread
{
int num, count=1; public MyThread(int i){
System.out.println(" 创建第【"+i+"】个线程!");
num = i ;
} public void run(){
while(true){
System.out.println("线程["+num+"] is running, 线程总数count="+count);
if(++count==6)
return;
}
} public static void main(String[] args)
{
for(int j=0; j<5; j++){
new MyThread(j+1).start();
}
}
}
也就是说,第一个创建的线程都有自己的count变量,
如果实现的是Runable接口的类,则类的所有实例都会共享一个类变量,
才会出现你想象的那中情况!
public static int iThreadCount =0;
} public static void main(String[] args)
{
for(int j=0; j<5; j++){
new MyThread(j+1).start();
SysComm.iTreadCount++;
}
}
产生的5个thread实例,都有自己的num,count。
当JVC分派到某个线程run的时候, 只会改变本线程的count值。