code: private String getUtf8String(int refIndex) throws InvalidClassFileFormatException {
          checkConstantPoolIndex(refIndex);
          Constant refConstant = constantPool[refIndex];
          checkConstantTag(refConstant, IClassConstants.CONSTANT_Utf8);
          return (String) refConstant.data[0];
      }
docs: Get the UTF-8 string constant at given constant pool index.
  
  @param refIndex
  the constant pool index
  @return the String at that index
  @throws InvalidClassFileFormatException