Annotations are used to attach metadata to code. This is created using the annotation keyword:

public annotation class JvmStatic

In the most common cases, annotations are used by annotation processing tools to generate or modify code. Let's look at the following example:

class Example1 {
    companion object {
        fun companionClassMember() {}
    }
}

The Kotlin bytecode viewer shows the following code:

public final class Example1 {
   public static final Example1.Companion Companion = new Example1.Companion((DefaultConstructorMarker)null);

   public static final class Companion {
      public final void companionClassMember() {
      }

      private Companion() {
      }

      // $FF: synthetic method
      public Companion(DefaultConstructorMarker $constructor_marker) {
         this();
      }
   }
}

As you can see, the Example1 class contains the nested Companion class that contains the companionClassMember method. We can mark the companionClassMember method when the @JvmStatic annotation and the decompiled code to Java code version looks as follows:

public final class Example1 {
   public static final Example1.Companion Companion = new Example1.Companion((DefaultConstructorMarker)null);

   @JvmStatic
   public static final void companionClassMember() {
      Companion.companionClassMember();
   }

   public static final class Companion {
      @JvmStatic
      public final void companionClassMember() {}

      private Companion() {}

      // $FF: synthetic method
      public Companion(DefaultConstructorMarker $constructor_marker) {
         this();
      }
   }
}

The preceding snippet contains the additional static companionClassMember function in the Example1 class that invokes the method of the Companion class. Using the @JvmStatic annotation, we tell the compiler to generate an additional method that can be used from the Java side.