Category: pmd
Rule Key: pmd:NonThreadSafeSingleton
⚠️ This rule is deprecated in favour of S2444.
Non-thread safe singletons can result in bad state changes. Eliminate static singletons if possible by instantiating the object directly. Static singletons are usually not needed as only a single instance exists anyway. Other possible fixes are to synchronize the entire method or to use an initialize-on-demand holder class (do not use the double-check idiom). See Effective Java, item 48.