code: public void setXsdInput(final String xsdInputPath) {
          if (xsdInputPath == null) {
              throw (new IllegalArgumentException(
                      "You must provide a source folder or file"));
          }
          File xsdInput = new File(xsdInputPath);
          if (xsdInput.exists()) {
              if (xsdInput.isDirectory() && xsdInput.list().length == 0) {
                  throw new IllegalArgumentException("Folder '" + xsdInputPath
                          + "' is empty");
              }
          } else {
              throw new IllegalArgumentException("Input file or folder '"
                      + xsdInputPath + "' not found");
          }
          this.xsdInput = xsdInput;
      }
docs: Check the input parameter and keep it only if it is valid.
  
  @param xsdInputPath a file or folder name (relative or absolute)