Java线程池实际场景问题！！面试必问 求解答
核心线程数7，最大线程数10，等待队列长20
有40个任务 如果40个任务在两秒内全部过来（每个任务执行时间大于两秒），执行拒绝策略，要拒绝多少任务？
答案是10个
从测试结果可以看出，线程池会先将前7个任务（0-6）先放到核心线程池，然后 7 到 26 的任务来了之后被放入了等待队列中，后面id 27-29 因为等待队列满了，开始为这些任务创建新线程 直到到达最大线程数。从30 开始到来的任务都会被拒绝了。
测试代码：
public class MyRunnable implements Runnable{
private String id;
public MyRunnable(String id) {
this.id = id;
}
@Override
public void run() {
// System.out.println(Thread.currentThread().getName() + " Start Time = " + new Date());
processCommand();
// System.out.println(Thread.currentThread().getName() + " End Time = " + new Date());
}
private void processCommand() {
try {
System.out.println("ID: " + this.id + " are in process");
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
@Override
public String toString() {
return this.id;
}
}
public class ThreadPoolExecutorDemo {
public static final int CORE_POOL_SIZE = 7;
public static final int MAX_POOL_SIZE = 10;
public static final int QUEUE_CAPACITY = 20;
public static final long KEEP_ALIVE_TIME = 1L;
public static void main(String[] args) {
ThreadPoolExecutor executor = new ThreadPoolExecutor(
CORE_POOL_SIZE,
MAX_POOL_SIZE,
KEEP_ALIVE_TIME,
TimeUnit.SECONDS,
new ArrayBlockingQueue<>(QUEUE_CAPACITY),
new ThreadPoolExecutor.AbortPolicy());
for (int i = 0; i < 40; i++) {
Runnable worker = new MyRunnable("" + i);
try {
executor.execute(worker);
} catch (Exception e) {
System.out.println("Execute ID:" + i + " got exception with details: " + e.getMessage());
}
}
executor.shutdown();
while (!executor.isTerminated()) {
}
System.out.println("Finished all threads");
}
} 
查看9道真题和解析
