Returning a reference to a mutable object value stored in one of the object's fields exposes the internal representation of the object.  If instances are accessed by untrusted code, and unchecked changes to the mutable object would compromise security or other important properties, you will need to do something different. Returning a new copy of the object is better approach in many situations.

See CWE-374: Passing Mutable Objects to an Untrusted Method.

This method contains an unsynchronized lazy initialization of a static field. After the field is set, the object stored into that location is further updated or accessed. The setting of the field is visible to other threads as soon as it is set. If the further accesses in the method that set the field serve to initialize the object, then you have a very serious multithreading bug, unless something else prevents any other thread from accessing the stored object until it is fully initialized.

Even if you feel confident that the method is never called by multiple threads, it might be better to not set the static field until the value you are setting it to is fully populated/initialized.

See CWE-543: Use of Singleton Pattern Without Synchronization in a Multithreaded Context.

A public static method returns a reference to a mutable object or an array that is part of the static state of the class. Any code that calls this method can freely modify the underlying array. One fix is to return a copy of the array.

Class names should be nouns, in mixed case with the first letter of each internal word capitalized. Try to keep your class names simple and descriptive. Use whole words-avoid acronyms and abbreviations (unless the abbreviation is much more widely used than the long form, such as URL or HTML).