test lock demo.

Signed-off-by: Flycoding <Flycoding@yeah.net>
test ForkJoinPool.

Signed-off-by: Flycoding <Flycoding@yeah.net>
test ThreadLocalRandom.

Signed-off-by: Flycoding <Flycoding@yeah.net>
add PC demo2.

Signed-off-by: Flycoding <Flycoding@yeah.net>