Why do Java compiled classes contain names like \'Find$1.class\'?

Denoting Inner Classes in Java Compiled Classes

In Java, when exporting an application to a JAR file, certain classes may contain the class name followed by a dollar sign and a number, such as Find$1.class. This occurs because Java compiles inner classes, including anonymous inner classes, separately from the main class.

Inner classes, defined within another class, enable object-oriented programming concepts like encapsulation and code reusability. They are compiler-generated and their class files have the following naming convention:

• Named inner classes: OuterClass$InnerClass.class
• Anonymous inner classes: OuterClass$1.class (where 1 represents the anonymous class)

For instance, in the following code:

<code class="java">public class OuterClass {
    public class InnerClass {
        // ...
    }

    public static void main(String[] args) {
        OuterClass.InnerClass inner = new InnerClass();
    }
}</code>

Compilation will generate the following class files:

• OuterClass.class
• OuterClass$InnerClass.class

The dollar sign in class file names serves as a separator to differentiate between outer and inner classes. It indicates that the inner class belongs to the specified outer class.

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