【实践 -- 我的感悟 -- Thread】经典demo ---main方法在静态代码区 -- Thread类只包含一个 属性i和一个方法run，与main无关！！！！！！！！！！！！！！！！！！！

1、demo，注意主线程，以及2个new出来的线程都共享一个静态资源 int i。注意输出结果（此处存在线程安全问题）

如果对方法加锁，是否结果会变成100 行？？？！！！

注：开始执行时，main方法在静态代码区？？执行，然后new 2个FirstThread类，每个类
只包含一个 属性i，和一个方法run，和main方法无关。

package ch16.mutli.thread;

public class FirstThread extends Thread{

    
    private volatile static int i;
    @Override
    public void run(){
//        setName("songxiaohu");
        for( ; i < 100; i++){
            System.out.println(getName() + " " + i);
        }
    }
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        for (; i < 100; i++) {
//            for (int i = 0; i < 100; i++) {
            System.out.println(Thread.currentThread().getName() + " " + i);
            if (i==20) {
                new FirstThread().start();
                new FirstThread().start();
            }
            
        }
    }

}

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