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Public ThreadPoolExecutor (int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue workQueue, ThreadFactory threadFactory, RejectedExecutionHandler handler) {...} thread saturation strategy

1. When will it be saturated?

When the core thread corePoolSize is full and the blocking queue is full, it will determine whether the current number of threads is less than the maximum number of threads, and decide whether to create new threads. If the total number of threads created is greater than maximumPoolSize, RejectedExecetionHandler will be triggered.

two。 What are the saturation strategies?

JDK mainly provides four saturation strategies to choose from. All four strategies are implemented in ThreadPoolExcutor as static inner classes.

AbortPolicy abort policy, DiscardPolicy discard policy, DiscardOldestPolicy discard old task policy, CallerRunsPolicy caller run

ThreadPoolExecutor.AbortPolicy: discards the task and throws a RejectedExecutionException exception.

ThreadPoolExecutor.DiscardPolicy: also discards the task, but does not throw an exception.

ThreadPoolExecutor.DiscardOldestPolicy: discard the first task in the queue and then try to execute the task again (repeat this process)

ThreadPoolExecutor.CallerRunsPolicy: the task is handled by the calling thread

Four thread pools encapsulated by 3.JUC

NewCachedThreadPool 、 newFixedThreadPool 、 newScheduledThreadPool 、 newSingleThreadExecutor

Thread exception handling

Let's start with the conclusion:

1. The logic in the run function in runnable must be try...catch

/ / if submit is used, if try catch is not added here, the exception will be "eaten" by PULL_TASK_EXECUTOR.execute (new Runnable () {@ Override public void run () {try {} catch (Exception e) {}).

It means that the biggest difference between the two is exception handling. In execute, if you don't implement a handler, then he uses the default handler to handle the exception. If you implement a handler,

He will use the instantiated handler, but for submit, the exception is bound to Future, but when future.get () is called, these exceptions will be thrown to you, which means that you define the handler

In fact, it is ineffective.

Public static void main (String [] args) {System.out.println ("start"); try {Executors.ASYNC_SERVICE_EXECUTOR.submit (()-> {System.out.println ("task start..."); Object obj = null; String str= obj.toString (); System.out.println ("str=") }); System.out.println ("end");} catch (Exception e) {log.error (e.getMessage ());}}

two。 The thread directly overrides the entire method

/ / in threaded mode Thread t = new Thread (); t.setUncaughtExceptionHandler (new Thread.UncaughtExceptionHandler () {public void uncaughtException (Thread t, Throwable e) {LOGGER.error (t + "throws exception:" + e);}}) / / if it is thread pool mode: ExecutorService threadPool = Executors.newFixedThreadPool (1, r-> {Thread t = new Thread (r); t.setUncaughtExceptionHandler ((T1, e)-> LOGGER.error (T1 + "throws exception:" + e)); return t;}) Thank you for reading, the above is the content of "Java thread pool satiety, rejection strategy and exception handling mechanism case analysis". After the study of this article, I believe you have a deeper understanding of Java thread pool satiety, rejection strategy and exception handling mechanism case analysis, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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