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8188241: Improve numerical code in StampedLock example code

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Reviewed-by: martin, psandoz, darcy
This commit is contained in:
Doug Lea 2017-10-03 13:32:04 -07:00
parent feab9efa52
commit dfce305868
1 changed files with 8 additions and 6 deletions

14
src/java.base/share/classes/java/util/concurrent/locks/StampedLock.java

@ -151,18 +151,20 @@ import jdk.internal.vm.annotation.ReservedStackAccess;
* }
*
* double distanceFromOrigin() { // A read-only method
* double currentX, currentY;
* long stamp = sl.tryOptimisticRead();
* double currentX = x, currentY = y;
* if (!sl.validate(stamp)) {
* stamp = sl.readLock();
* do {
* if (stamp == 0L)
* stamp = sl.readLock();
* try {
* // possibly racy reads
* currentX = x;
* currentY = y;
* } finally {
* sl.unlockRead(stamp);
* stamp = sl.tryConvertToOptimisticRead(stamp);
* }
* }
* return Math.sqrt(currentX * currentX + currentY * currentY);
* } while (stamp == 0);
* return Math.hypot(currentX, currentY);
* }
*
* void moveIfAtOrigin(double newX, double newY) { // upgrade