To put it simply, enumerable classes in Java are weird.

Writing vs. Compiled

Enumerable classes get transformed from being an enum type into a class type (final, extends Enum) at the point of compilation.

Example (No-Arguments Constructor)

Pre-compilation

public enum Example {
	ONE, TWO, THREE, FOUR
}

Decompiled

public final class Example extends java.lang.Enum<Example> {
  public static final Example ONE;
  public static final Example TWO;
  public static final Example THREE;
  public static final Example FOUR;
  private static final Example[] $VALUES;
  public static Example[] values();
  public static Example valueOf(java.lang.String);
  private Example();
  private static Example[] $values();
  static {};
}

Help

Decompiled via javap -p Example.class. See javap for more information on how to use javap.

Comparison

Taking a look at the pre-compiled and decompiled code - it is quite apparently different. This is because the enum type is not a part of the JVM instruction set.

When referencing an enumerable field - you’re just referencing an instance of the enum.

Understanding generated fields/methods

Note

All of these assume that you have not added any new fields/methods. Those ae treated as regular and do not need any additional clarification.

Static Fields

Within an enum there is $n+1$ static fields:

• $n$ being the number of enumerable instances (instance of the class itself - i.e., ONE, TWO, THREE, and FOUR from Understanding Enum Classes)
• $1$ being $VALUES - a static field which stores references to all enumerable instances within.

Research Sources

1. desugaring-java/enum-internals.adoc at master · ndru83/desugaring-java
2. Enum (Java Platform SE 8 )