executors: ExecutorService lifecycle companion code

Adds the executors module: shutdown() vs shutdownNow(), the graceful two-phase shutdown pattern, AutoCloseable/try-with-resources (JDK 19+), newVirtualThreadPerTaskExecutor() timing vs a bounded pool, and the submit()-without-get() lost-exception trap. 5 runnable demos, 1 JUnit correctness test class (23 tests), 6 captured output transcripts. Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01FhzLY5p6okFva3qsnsRyvM
2026-09-30 06:54:17 +00:00
parent 55ee850a75
commit bc5153d2a5
17 changed files with 607 additions and 0 deletions
@@ -0,0 +1,13 @@
+=== execute(): uncaught exception reaches the default handler, gets printed ===
+Exception in thread "pool-1-thread-1" java.lang.RuntimeException: boom from execute()
+	at com.ankurm.executors.LostExceptionTrapDemo.lambda$main$0(LostExceptionTrapDemo.java:22)
+	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1090)
+	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:614)
+	at java.base/java.lang.Thread.run(Thread.java:1474)
+
+=== submit(): same exception, but nobody calls get() - dead silence ===
+main: task's Future exists (isDone=true), but its exception was never printed anywhere - it's just sitting inside the Future
+
+=== submit() + get(): the SAME exception, now surfaced by calling get() ===
+main: caught ExecutionException, cause = java.lang.RuntimeException: boom from submit(), retrieved via get()
+done