How to List all files in a directory

import java.io.File;
import java.util.ArrayList;
import java.util.List;

public List getAllFilesInDirectory(String directory) {

String files;
File folder = new File(directory);
File[] listOfFiles = folder.listFiles();
List allFiles = new ArrayList<>();

for (int i = 0; i < listOfFiles.length; i++)
{
if (listOfFiles[i].isFile())
{
files = listOfFiles[i].getName();
//System.out.println(files);
allFiles.add(files);
}
}
return allFiles;
}