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I have some classes that are used as Singletons. They share some basic functionality and extend the same ancestor from a library which in turn isn't normally used as a Singleton. If I put the common functionality in a base class that inherits from the common ancestor, I get a class which makes no sense to instantiate, so I made it abstract. Also, because the classes are all used as Singletons, they should all have an init() and a getInstance() method, which are both static. All the constructors are of course non-public. Now, since static is an illegal modifier for abstract methods, the following doesn't work, although this would be exactly what I want: class Base extends LibraryClass { protected Base() { // ... constructor } // ... common methods // ILLEGAL! public static abstract void init(); public static abstract <T extends Base>T getInstance(); } class A extends Base { private static A _INSTANCE; private A() { super(); } public static void init() { _INSTANCE = new A(); } public static A getInstance() { return _INSTANCE; } } I could just leave out the illegal lines in the base class and be done with it. But how do I express that every child of Base must have these methods?

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