java.util.concurrent · java.base · since Java 1.5

ThreadPoolExecutor

declaration

public class ThreadPoolExecutor extends AbstractExecutorService

The configurable pool behind the factories: core/max size, keep-alive, work queue, thread factory, and rejection policy — every production pool decision in one constructor.

Bound the queue + choose a rejection policy, or overload becomes an OOM instead of a 503

Key methods

`ThreadPoolExecutor(core, max, keepAlive, unit, queue, factory, handler)`	The full policy constructor.
`int getActiveCount() / long getCompletedTaskCount()`	Monitoring hooks.
`CallerRunsPolicy / AbortPolicy / DiscardPolicy`	Rejection handlers — CallerRuns gives natural backpressure.