A non-static nested class in Java contains an implicit reference to an instance of the parent class. Thus to instantiate a Node, you would need to also have an instance of Stack. In a static context (the main method), there is no instance of Stack to refer to. Thus the compiler indicates it can not … Read more
I would declare inner-classes in the bottom of the file – usually you’re not interested in their implementations and just want to get to your main class’ methods, so they shouldn’t get in the way.
Clever example! But it’s actually a somewhat boring explanation – there’s no visibility problem, you simply have no way of referring to t1 directly from T3 because super.super isn’t allowed. T2 can’t access its own t1 field directly since it’s private (and child classes don’t inherit their parent’s private fields), but super is effectively an … Read more
I think you want to declare the HashPerson class as static. Otherwise it can only be instantiated in the context of the containing class, either in a method of the containing class or using code like this: ContainingClass container = new ContainingClass(); HashPerson william = container.new HashPerson(“willy”); Actually, my rule-of-thumb is to make any nested … Read more
Select the class name. Refactor > Move or press F6 Select “Move inner class Foo to upper level”
Inner classes are best for the purpose of logically grouping classes that are used in one-place. For example, if you want to create class which is used by ONLY enclosing class, then it doesn’t make sense to create a separate file for that. Instead you can add it as “inner class” As per java tutorial: … Read more
Well first, let’s all relax, and please put that gun down. OK. Now the reason the language insists on that is that it cheats in order to provide your inner class functions access to the local variables they crave. The runtime makes a copy of the local execution context (and etc. as appropriate), and thus … Read more
Private methods can not be overridden (private methods are not inherited!) In fact, it makes no difference if you declare a private method final or not. The two methods you have declared, Boom.touchMe and Boom.Inner.touchMe are two completely separate methods which just happen to share the same identifier. The fact that super.touchMe refers to a … Read more
They’re inner (nested non-static) classes: public class Outer { public class Inner { public void foo() { … } } } You can do: Outer outer = new Outer(); outer.new Inner().foo(); or simply: new Outer().new Inner().foo(); The reason for this is that Inner has a reference to a specific instance of the outer class. Let … Read more
enum types that are defined as nested types are always implicitly static (see JLS §8.9. Enums) You can’t have a static nested type inside a non-static one (a.k.a an “inner class”, see JLS §8.1.3. Inner Classes and Enclosing Instances). Therefore you can’t have an enum inner type inside a non-static nested type.