# Nested & Inner Classes — Core Java

Source: https://www.geekswithgeeks.com/en/core-java/java-inner-classes

> Distinguish static nested classes, non-static inner classes, local classes and anonymous classes, and see when each earns its keep.

## Static nested vs inner

A **static nested class** (`static class Node {...}`) is just a normal class namespaced inside another — it has no link to an outer instance. A **non-static inner class** is tied to an enclosing instance and can access its fields directly, but needs `outer.new Inner()` to create.

## An inner class in action

Because `Iterator` here is non-static, it can read `items` directly without the container passing it in explicitly.

```java
class Playlist {
    private final List<String> items = new ArrayList<>();

    class Cursor {                 // non-static inner class
        int pos = 0;
        String next() { return items.get(pos++); }
    }
}

Playlist p = new Playlist();
Playlist.Cursor c = p.new Cursor();
```

## Local & anonymous classes

A **local class** is declared inside a method body, visible only there. An **anonymous class** (`new Comparator<String>() { ... }`) declares and instantiates an unnamed one-off subclass in a single expression — largely superseded by lambdas for functional interfaces, but still useful for classes with multiple methods or state.