AbstractMethod-Implementors are now immutable in order to ensuse thread-safety. Removed ununsed fields and variables.
Code-Cleanup: Use HashMap for error-list instead of HashTable.
The error-list is only used as local variable and does not need synchronization
Fix potential memory leak with DateFormats in ThreadLocals
ThreadLocals should not be used in a servlet container, because they may not be garbage collected, when the servlet is shutdown.
ThreadLocal-DateFormats in AbstractMethod have now been replaced by multiple date formats in a ConcurrentQueue.
A DateFormat is removed from the queue, used, and than reinserted. If the queue is empty, a new DateFormat is created and inserted.
The size of the queue should adapt to the maximum number of concurrently used DateFormats.