the reference answer GPT ᴼ ᴾ ᴱ ᴺ ᴬ ᴵ < br / > for a system, CRM system or other system in the actual operation process will face the problem of concurrency. Especially in high concurrency scenarios, system crashes or data anomalies may occur if concurrency is not considered.
Threads are one of the most important ways to deal with concurrency in Java. Tomcat itself was developed based on Java, so Tomcat also uses Java threads to handle concurrent requests. Tomcat's thread pool pre-creates a certain number of threads, and each time a request arrives, a thread is pulled from the pool to process the request. When processing is complete, the thread returns to the pool and waits for the next request.
In addition to Tomcat's thread pool, Java also supports custom threads. Custom threads can be implemented according to specific requirements, such as timing tasks, asynchronous processing, thread pooling, and so on. When dealing with concurrency issues, customizing threads allows us to have more flexibility in controlling the number of threads and how they execute, thus better coping with high concurrency scenarios.