public boolean isEmpty() {
    return staticFields.isEmpty()
        && instanceFields.isEmpty()
        && directMethods.isEmpty()
        && virtualMethods.isEmpty();
  }
Returns whether this instance is empty.

@return {@code true} if this instance is empty or {@code false} if at least one element has
    been added to it
android/android_framework/dex-maker/src/main/java/com/android/dx/dex/file/ClassDataItem.java