code: 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;
      }
docs: Get a class name from a CONSTANT_Class. Note that this may be an array
  (e.g., "[Ljava/lang/String;").
  
  @param index
  index of the constant
  @return the class name
  @throws InvalidClassFileFormatException