How to search file inside a specific folder in google API v3

As i am using v3 of google api,So instead of using parent and chidren list i have to use fileList, So now i want to search list of file inside a specific folder.
So someone can suggest me what to do?

Here is the code i am using to search the file :

private String searchFile(String mimeType,String fileName) throws IOException{
    Drive driveService = getDriveService();
    String fileId = null;
    String pageToken = null;
    do {
        FileList result = driveService.files().list()
                .setQ(mimeType)
                .setSpaces("drive")
                .setFields("nextPageToken, files(id, name)")
                .setPageToken(pageToken)
                .execute();
        for(File f: result.getFiles()) {
            System.out.printf("Found file: %s (%s)/n",
                    f.getName(), f.getId());
            if(f.getName().equals(fileName)){
                //fileFlag++;
                fileId = f.getId();
            }
        }
        pageToken = result.getNextPageToken();
    } while (pageToken != null);

    return fileId;
}

But in this method it giving me all the files that are generated which i don’t want.I want to create a FileList which will give file inside a specific folder.

Searching files by folder name is not yet supported. It’s been requested in this google forum but so far, nothing yet. However, try to look for other alternative search filters available in Search for Files.

Be creative. For example make sure the files within a certain folder contains a unique keyword which you can then query using

 fullText contains 'my_unique_keyword'

you can use this method to search the files from google drive.

    Files.List request = this.driveService.files().list();
    noOfRecords = 100;
    request.setPageSize(noOfRecords);
    request.setPageToken(nextPageToken);
    String searchQuery = "(name contains 'Hello')";
    if (StringUtils.isNotBlank(searchQuery)) {
        request.setQ(searchQuery);
    }
    request.execute();