shutdown
Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted. Invocation has no additional effect if already shut down.
This method does not wait for previously submitted tasks to complete execution. Use .awaitTermination to do that.
Throws
SecurityException
if a security manager exists and shutting down this ExecutorService may manipulate threads that the caller is not permitted to modify because it does not hold [ ]("modifyThread"), or the security manager's checkAccess method denies access.