docs: private @SlashedClassName
      String getClassName(int index) throws InvalidClassFileFormatException {
          if (index == 0) {
              return null;
          }
  
          checkConstantPoolIndex(index);
          Constant constant = constantPool[index];
          checkConstantTag(constant, IClassConstants.CONSTANT_Class);
  
          int refIndex = ((Integer) constant.data[0]).intValue();
          String stringValue = getUtf8String(refIndex);
  
          return stringValue;
      }