线程安全不安全的辅助理解，可以拿这个例子自己去运行看看

public class Test {
//LinkedList线程不安全
//List<Integer>list=new LinkedList<Integer>();
//Vector线程安全
List<Integer> list=new Vector<Integer>();

public static void main(String[] args)  {
Test test=new Test();

ThreadA tA = test.new ThreadA();
ThreadB tB = test.new ThreadB();

tA.start();
tB.start();
try{
tA.join();
tB.join();
}catch(InterruptedException e){
e.printStackTrace();
}
System.out.println("list size:"+test.list.size());

}
class ThreadA extends Thread{
@Override
public void run(){
super.run();
for(int i=0;i<100;i++){
list.add(i);
}
}
}
class ThreadB extends Thread{
@Override
public void run(){
super.run();
for(int i=0;i<100;i++){
list.add(i);
}
}
}
}