同步容器为什么会出现不安全情况？？？

public class Test {
static Vector vector = new Vector();
public static void main(String[] args) throws InterruptedException {
while(true) {
for(int i=0;i vector.add(i);
Thread thread1 = new Thread(){
public void run() {
for(int i=0;i vector.remove(i);
};
};
Thread thread2 = new Thread(){
public void run() {
for(int i=0;i vector.get(i);
};
};
thread1.start();
thread2.start();
while(Thread.activeCount()>10) {

        }
    }
}

}

容器里的数值和地址是变化的，remove或者add之后，你在get会发生位置偏移，获取的会出错，不安全