ptg
Listings
1 Bad way to sort a list. Don’t do this. . ..................xix
2 Less than optimal way to sort a list. . .................. xx
1.1 Non-thread-safe sequence generator. .................. 6
1.2 Thread-safe sequence generator. ..................... 7
2.1 A stateless servlet. . . . . ......................... 18
2.2 Servlet that counts requests without the necessary synchroniza-
tion. Don’t do this. ............................. 19
2.3 Race condition in lazy initialization. Don’t do this. .......... 21
2.4 Servlet that counts requests using
AtomicLong
. ............ 23
2.5 Servlet that attempts to cache its last result without adequate
atomicity. Don’t do this. . ......................... 24
2.6 Servlet that caches last result, but with unnacceptably poor con-
currency. Don’t do this. ........................... 26
2.7 Code that would deadlock if intrinsic locks were not reentrant. . . . 27
2.8 Servlet that caches its last request and result. ............. 31
3.1 Sharing variables without synchronization. Don’t do this. ...... 34
3.2 Non-thread-safe mutable integer holder. ................ 36
3.3 Thread-safe mutable integer holder. . .................. 36
3.4 Counting sheep. . ............................. 39
3.5 Publishing an object. . . ......................... 40
3.6 Allowing internal mutable state to escape. Don’t do this. . ...... 40
3.7 Implicitly allowing the
this
reference to escape. Don’t do this. . . . 41
3.8 Using a factory method to prevent the
this
reference from escap-
ing during construction. ......................... 42
3.9 Thread confinement of local primitive and reference variables. . . . 44
3.10 Using
ThreadLocal
to ensure thread confinement. .......... 45
3.11 Immutable class built out of mutable underlying objects. ...... 47
3.12 Immutable holder for caching a number and its factors. . ...... 49
3.13 Caching the last result using a volatile reference to an immutable
holder object. ................................ 50
3.14 Publishing an object without adequate synchronization. Don’t do
this. . .................................... 50
3.15 Class at risk of failure if not properly published. . .......... 51
4.1 Simple thread-safe counter using the Java monitor pattern. . . . . . 56
4.2 Using confinement to ensure thread safety. .............. 59
4.3 Guarding state with a private lock. . .................. 61
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