Day 2: Beyond Intrinsic Locks

Day 1 covered Java’s Thread class and the intrinsic locks built into every Java object. For a long time this was pretty much all the support that Java provided for concurrent programming. Java 5 changed all that with the introduction of java.util.concurrent. Today we’ll look at the enhanced locking mechanisms it provides.

Intrinsic locks are convenient but limited.

  • There is no way to interrupt a thread that’s blocked as a result of trying to acquire an intrinsic lock.

  • There is no way to time out while trying to acquire an intrinsic lock.

  • There’s exactly one way to acquire an intrinsic lock: a synchronized block.

    ​ 
    ​synchronized​(object) {
    ​ 
    use shared resources
    ​ 
    }

    This means that lock ...

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