public FolderJob createFolder(String folderName, Boolean crumbFlag) throws IOException {
        // https://gist.github.com/stuart-warren/7786892 was slightly helpful
        // here
        //TODO: JDK9+: Map.of(...)
        Map<String, String> params = new HashMap<>();
        params.put("mode", "com.cloudbees.hudson.plugins.folder.Folder");
        params.put("name", folderName);
        params.put("from", "");
        params.put("Submit", "OK");
        client.post_form(this.getUrl() + "/createItem?", params, crumbFlag);
        return this;
    }
public FolderJob createFolder ( String folderName , Boolean crumbFlag ) throws IOException { Map < String , String > params = new HashMap < > ( ) ; params . put ( "mode" , "com.cloudbees.hudson.plugins.folder.Folder" ) ; params . put ( "name" , folderName ) ; params . put ( "from" , "" ) ; params . put ( "Submit" , "OK" ) ; client . post_form ( this . getUrl ( ) + "/createItem?" , params , crumbFlag ) ; return this ; }
Create a folder on the server (as a subfolder of this folder)

@param folderName name of the folder to be created.
@param crumbFlag true/false.
@return
@throws IOException in case of an error.