What is the difference between an inner class and a nested class in programming?

In Java (and in Android), a nested class is any class declared within another class. Nested classes are of two types:

1. Static nested class — declared with the static modifier. It does not have direct access to the non-static members of the outer class.
2. Inner class — a nested class without the static modifier. It is associated with an instance of the outer class and has access to its non-static fields and methods.

Example:

class Outer {
    private int outerField = 10;

    static class StaticNested {
        void print() {
            // Cannot access outerField directly
            System.out.println("Static nested class");
        }
    }

    class Inner {
        void print() {
            // Can access outerField
            System.out.println("Inner class, outerField = " + outerField);
        }
    }
}

Thus, the main difference is that the inner class is associated with an instance of the outer class and can access its non-static members, while the static nested class is not.