线程池
1、 理解线程池原理;
future可能出现的问题
1) 取消;
2) 异常:
2.1) 超时异常;
2.2) 中断异常;
2.3) 执行异常;
2、 数据库连接池要设置多少?
3、 线程池要设置多少?
io密集型一般设置为cpu数量*2
cpu密集型一般设置为cpu+1(多线程+主线程);
为什么加1呢?
我想应该可能是主线程;
corepool 50;
blockingquene 200;
max 500;(防止溢出;)
keepAliveSeconds:600;线程存活时间;
AbortPolicy:抛出异常;RejectedExecutionException;虚拟机不会关闭,程序处于阻塞状态;
只执行blockingquene+maxpoolThreads;
pool-1-thread-4 is running
pool-1-thread-4 is running
pool-1-thread-4 is running
CallerRunsPolicy:用调用者所在线程来执行当前任务,比如说调用者在main线程,缺点:没有了多线程,没有了任何意义;
全部执行完;
main is running
main is running
main is running
pool-1-thread-6 is running
pool-1-thread-6 is running
pool-1-thread-6 is running
DiscardOldestPolicy:不抛出异常;虚拟机关闭,不处于阻塞状态;
丢弃队列里最近的一个任务,并执行当前任务;
只执行blockingquene+maxpoolThreads;
pool-1-thread-3 is running
pool-1-thread-4 is running
pool-1-thread-4 is running
DiscardPolicy:直接丢弃当前任务,不处理;
只执行blockingquene+maxpoolThreads;
pool-1-thread-5 is running
pool-1-thread-5 is running
pool-1-thread-6 is running