Building Blocks - Java Concurrency in Practice - page 92

that the size of the Vector does not change between calling size and get , as shown in
Listing 5.2 .
The risk that the size of the list might change between a call to size and the corresponding
call to get is also present when we iterate through the elements of a Vector as shown in
Listing 5.3 .
This iteration idiom relies on a leap of faith that other threads will not modify the Vector
between the calls to size and get . In a single-threaded environment, this assumption is
perfectly valid, but when other threads may concurrently modify the Vector it can lead to
trouble. Just as with getLast , if another thread deletes an element while you are iterating
through the Vector and the operations are interleaved unluckily, this iteration idiom throws
ArrayIndexOutOfBoundsException .
Listing 5.2. Compound Actions on Vector Using Client-side Locking.
Listing 5.3. Iteration that may Throw ArrayIndexOutOfBoundsException .