Java function to read a CSV file
The code can be simplified and improved in several ways, and the inner loop can be made tighter. Let me show you how:

private static List&lt;List&lt;String&gt;&gt; readTXTFile(String csvFileName) throws IOException {

    String line = null;
    BufferedReader stream = null;
    List&lt;List&lt;String&gt;&gt; csvData = new ArrayList&lt;List&lt;String&gt;&gt;();

    try {
        stream = new BufferedReader(new FileReader(csvFileName));
        while ((line = stream.readLine()) != null) {
            String[] splitted = line.split(",");
            List&lt;String&gt; dataLine = new ArrayList&lt;String&gt;(splitted.length);
            for (String data : splitted)
                dataLine.add(data);
            csvData.add(dataLine);
        }
    } finally {
        if (stream != null)
            stream.close();
    }

    return csvData;

}



A method should throw an exception as specific as possible, here it's better to use IOException instead of simply Exception
Whenever possible, return interface types instead of concrete classes. Using List is preferred to using Vector, this allows you the flexibility to change the implementation of the collection later
Talking about collections: Vector is thread-safe and synchronized in many of its public methods, that can cause a performance hit. If you don't need that, it's better to use ArrayList, it's a drop-in replacement and won't incur in the performance penalty of synchronization. 
There's a simpler way to instantiate a BufferedReader, using a FileReader instead of using an InputStreamReader plus a FileInputStream. Besides, FileReader will take care of pesky details regarding character encoding
There's a simpler way to add elements to the last List added to csvData, as shown in the code
There's a simpler way to iterate through the String[] returned by split(), using an enhanced loop
Don't forget to close your streams! preferably inside a finally block


If you don't need to add more elements to the returned List&lt;List&lt;String&gt;&gt;, you can use the following alternate version. It's faster because it avoids copying the String[] of split elements, but it won't allow adding new elements, as per the contract of asList():

private static List&lt;List&lt;String&gt;&gt; readTXTFile(String csvFileName) throws IOException {

    String line = null;
    BufferedReader stream = null;
    List&lt;List&lt;String&gt;&gt; csvData = new ArrayList&lt;List&lt;String&gt;&gt;();

    try {
        stream = new BufferedReader(new FileReader(csvFileName));
        while ((line = stream.readLine()) != null)
            csvData.add(Arrays.asList(line.split(",")));
    } finally {
        if (stream != null)
            stream.close();
    }

    return csvData;

}