一、死锁
有A，B两把锁，t1持有A想获取B，t2持有B想获取A，导致t1 t2两个线程最终都进入阻塞状态的现象
public class Test8 {
private final static Logger LOGGER = LoggerFactory.getLogger(Test8.class);
private final static Object lockA= new Object();
private final static Object lockB= new Object();
public static void main(String[] args) {
Thread t1 = new Thread(new Runnable() {
@Override
public void run() {
synchronized (lockA){
LOGGER.info("持有A");
synchronized (lockB){
LOGGER.info("持有B");
}
}
}
},"t1");
Thread t2 = new Thread(new Runnable() {
@Override
public void run() {
synchronized (lockB){
LOGGER.info("持有B");
synchronized (lockA){
LOGGER.info("持有A");
}
}
}
},"t2");
t1.start();
t2.start();
}
}
如何解决:
可以使用ReentrantLock中的tryLock,或者lockInterruptibly，这些能够在某些条件下主动放弃争抢锁的方法
二、活锁
两个线程互相改变对方的结束条件，最终两个线程都不能正常结束的现象
public class Test8 {
private final static Logger LOGGER = LoggerFactory.getLogger(Test8.class);
private static volatile int i=10;
public static void main(String[] args) {
Thread t1 = new Thread(new Runnable() {
@Override
public void run() {
while (i>0){
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
i--;
LOGGER.info("i:"+i);
}
}
},"t1");
Thread t2 = new Thread(new Runnable() {
@Override
public void run() {
while (i<20){
try {
Thread.sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
i++;
LOGGER.info("i:"+i);
}
}
},"t2");
t1.start();
t2.start();
}
}
解决办法:增加随机的睡眠时间，或者t2里写i=i+20 这样t2会有更大的可能先结束，然后就没有线程修改t1的结束条件了，t1就可以结束了
三、饥饿
一个线程由于优先级太低始终抢不到cpu执行权而不能被执行，所以一直不能结束
标签：Thread,t2,t1,活跃性,线程,new,public From： https://www.cnblogs.com/chengxuxiaoyuan/p/16947697.html