非静态方法中实现私有抽象静态类的匿名类是否持有外部类引用？

Short Answer: No, it does NOT. #

Detailed Explanation #

Let's break this down clearly, based on Java's core rules for inner classes and anonymous classes:

1. Static inner classes have no implicit outer class ties
   Your Inner class is marked static—this makes it a standalone nested class that’s only tucked inside Concept for structure, not because it depends on a Concept instance. Any subclass of a static inner class (including your anonymous subclass here) inherits this independence: it doesn’t automatically carry a reference to the outer Concept class.

2. Anonymous classes only hold outer references when necessary
   An anonymous class will only get an implicit outer class reference if two conditions are met:

   • It’s created in a non-static context (like your func() instance method), AND
   • It accesses instance members of the outer class (e.g., Concept.this.someInstanceField or an instance method) OR it’s a subclass of a non-static inner class.

   In your code, the anonymous subclass of Inner only implements bar() to return a new Object—it never interacts with any instance-specific part of Concept. There’s no reason for it to hold a reference to a Concept instance, so Java doesn’t generate one.

Quick Verification Tip (If You Want to Confirm) #

If you’re curious to see this in action:

• Use a Java decompiler (like the built-in javap tool) to inspect the anonymous class’s bytecode. You’ll notice its constructor doesn’t take a Concept instance as a parameter—unlike anonymous classes that do hold outer references, which always have this parameter to pass the outer instance.
• Try adding a reference to a Concept instance member in bar() (e.g., return Concept.this;). You’ll see the compiler now generates code to pass the outer Concept instance to the anonymous class—but this doesn’t happen in your original code.

内容的提问来源于stack exchange，提问作者Brian K