Attempts to stop all actively executing tasks, halts the
processing of waiting tasks, and returns a list of the tasks
that were awaiting execution.
<p>This method does not wait for actively executing tasks to
terminate. Use {@link #awaitTermination awaitTermination} to
do that.
<p>There are no guarantees beyond best-effort attempts to stop
processing actively executing tasks. For example, typical
implementations will cancel via {@link Thread#interrupt}, so any
task that fails to respond to interrupts may never terminate.
@return list of tasks that never commenced execution
@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 {@link
java.lang.RuntimePermission}{@code ("modifyThread")},
or the security manager's {@code checkAccess} method
denies access.
Attempts to stop all actively executing tasks, halts the processing of waiting tasks, and returns a list of the tasks that were awaiting execution.
<p>This method does not wait for actively executing tasks to terminate. Use {@link #awaitTermination awaitTermination} to do that.
<p>There are no guarantees beyond best-effort attempts to stop processing actively executing tasks. For example, typical implementations will cancel via {@link Thread#interrupt}, so any task that fails to respond to interrupts may never terminate.
@return list of tasks that never commenced execution @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 {@link java.lang.RuntimePermission}{@code ("modifyThread")}, or the security manager's {@code checkAccess} method denies access.