Virtual threads: synchronized pins the carrier, ReentrantLock does not

A virtual thread that blocks inside a synchronized block holds its carrier platform thread hostage. The same code under a ReentrantLock unmounts cleanly. With an uncontended lock per task, the only difference left is pinning - and it serialises everything.

• Utilities: a private constructor with only static members documents a utility class
• Utilities: new Random(seed) produces the same sequence every run
• Utilities: UUID.nameUUIDFromBytes produces the same UUID for the same input
• Utilities: Base64 encodes bytes into ASCII text and decodes them back
• Utilities: HexFormat converts bytes to and from a hex string
• Utilities: Arrays.deepEquals compares nested arrays, equals does not

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Published 2026-08-25

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