There’s no implicit inheritance involved as far as I can tell. I would have expected this to be okay – although I can imagine weirdness if A and B were generic. It’s specified in section 10.1.4 of the spec: When a class B derives from a class A, it is a compile-time error for A … Read more
You can’t forward-declare a nested class like that. Depending on what you’re trying to do, maybe you can use a namespace rather than a class on the outer layer. You can forward-declare such a class no problem: namespace Outer { struct Inner; }; Outer::Inner* sweets; // Outer::Inner is incomplete so // I can only make … Read more
Drink.COFFEE.getGroupName(); Drink.COFFEE.COLUMBIAN.getLabel(); First off, that sample code you gave violates the “law of demeter” somewhat – as the COLUMBIAN instance field is only used to retrieve the label. Also, with that structure, COLUMBIAN has to be an instance of the COFFEE enum, but I don’t think that’s what you’re really going for here. someMethod(Drink type) … Read more
This question is pretty old, and I don’t know if it would have worked with the version of WPF back in 2010, but now you can make it work by using the “real” (internal) name of the nested type: <local:A+B /> If you’ve ever looked a disassembled code, that’s how nested types look like: ParentTypeName+Nested
You can make the inner class package private which means that it will only be accessible from other classes in exactly the same package. This is also done quite frequently for hidden classes inside the standard JDK packages like java.lang or java.util. in pkg/MyClass.java public class MyClass { … } in pkg/MyHiddenClass.java class MyHiddenClass { … Read more
You can get rid of the warning as follows: package com.example.bugs; public class WeirdInnerClassJavaWarning { private static class InnerClass { protected InnerClass() {} // This constructor makes the warning go away public void doSomething() {} } final private InnerClass anInstance; { this.anInstance = new InnerClass(); this.anInstance.doSomething(); } } As others have said, Eclipse is complaining … Read more
I would be a bit reluctant to use nested classes here. What if you created an abstract base class for a “multimedia driver” to handle the back-end stuff (workhorse), and a separate class for the front-end work? The front-end class could take a pointer/reference to an implemented driver class (for the appropriate media type and … Read more
Actually there is a complete and simple solution to this problem that doesn’t involve modifying the client code or creating an interface. This solution is actually faster than the interface-based solution for most cases, and easier to code. public class Journal { private static Func<object, JournalEntry> _newJournalEntry; public class JournalEntry { static JournalEntry() { _newJournalEntry … Read more
After having asked more or less the same question here myself, I wanted to share the (apparently) updated answer for C++11: Quoted from https://stackoverflow.com/a/14759027/1984137: standard $11.7.1 “A nested class is a member and as such has the same access rights as any other member. The members of an enclosing class have no special access to … Read more
A pattern that I particularly like is to combine nested classes with the factory pattern: public abstract class BankAccount { private BankAccount() {} // prevent third-party subclassing. private sealed class SavingsAccount : BankAccount { … } private sealed class ChequingAccount : BankAccount { … } public static BankAccount MakeSavingAccount() { … } public static BankAccount … Read more