Can you name built-in classes in programming languages?

In Java, nested (inner) classes are classes declared within another class. They come in several types:

• Static nested classes: declared with the static modifier. They do not have access to the non-static members of the outer class.

• Inner classes: non-static classes within another class. They have access to the members of the outer class.

• Local classes: declared within a method, accessible only within that method.

• Anonymous classes: classes without a name, declared and instantiated simultaneously, often used for implementing interfaces or inheritance.

Example of an inner class:

public class Outer {
    private int x = 10;
    class Inner {
        void print() {
            System.out.println(x); // access to outer class field
        }
    }
}

Nested classes help logically group code and provide encapsulation.