Why do Java compiled classes in JAR files have dollar signs and numbers in their file names?

Java Compiled Classes Exhibiting Dollar Signs within File Names

Question:

In exported JAR files created using Eclipse, certain class files display the class name followed by a dollar sign and a number. For instance:

<code class="java">Find.class 
Find.class
Find.class
Find.class</code>

Is this a consequence of code size limitations, where larger classes are broken down into multiple smaller ones? Extensive online searches have yielded no relevant information. Can someone provide an explanation?

Answer:

These additional class files are a result of inner classes within the original class. Inner classes are nested within outer classes and are declared using the class keyword:

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

When a class containing inner classes is compiled, separate class files are generated for each inner class, following the naming convention OuterClass$InnerClass.class. Anonymous inner classes (those without a name) are assigned numerical identifiers, resulting in file names like OuterClass$1.class.

Contrary to popular belief, the size of the original class does not influence the creation of multiple class files. The presence of inner classes is the sole reason for this behavior.

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