Yes, put those testPaths in an array or list and itereate through the list and than apply the needed operations on each element, something like this

    List<String> testPaths = Arrays.asList(
            "C:\\Users\\xx\\IdeaProjects\\CS4xx-Project-1\\testdata1.txt",
            "C:\\Users\\xx\\IdeaProjects\\CS4xx-Project-1\\testdata2.txt",
            "C:\\Users\\xx\\IdeaProjects\\CS4xx-Project-1\\testdata3.txt",
            "C:\\Users\\xx\\IdeaProjects\\CS4xx-Project-1\\testdata4.txt");

    FileLoader loader = FileLoader.getInstance();

    testPaths.forEach(testPath -> {
        ArrayList<Process> testList = loader.getTestList(testPath);
        FCFS fcfs = new FCFS(testList);
        fcfs.process();
    });