JAVA: Adding an instace of my class "Gate" to a map is null

Question

I am having trouble with my code. This is my first time using a Map and for some reason the Gate that is added in the 2nd try block is null. I cannot spot the error. The error first shows itself in the last try block where i get nullpointer when i try to set the inputgates.

The file that is given the to the function has several lines where each line looks like this: starts with a name for the gate, then the type for the gate, then a number of inputgates. (Gates previouse created). There is a type of gate called signalgate that just acts as a startgate. Has no input, just an output. We are talking about NAND, AND, OR gates and such.

Thanks in advance!

public static String Capital(String s){
    String string = s.substring(0,1).toUpperCase() + s.substring(1).toLowerCase();
    string = string + "Gate";
    return string;
}

public static Map<String, Gate> createGates(File file){
    //variabler.
    BufferedReader bufferedReader = null;
    String[] lines = null;
    String line;
    Map<String, Gate> map = new LinkedHashMap<String, Gate>();
    int index = 0;
    Gate g;

    try{
        //tests reading the file
        bufferedReader = new BufferedReader(new FileReader(file));
        //As long as there still are lines left
        while((line = bufferedReader.readLine()) != null){
            index++;
            //as long as the line's not a comment.
            if(line.trim().charAt(0) == '*' || line.trim().charAt(0) == '/'){
                continue;
            }else{
                lines = line.split("\\s+");
            }
            //Gör namnet till att börja med stor bokstav och resten blir små bokstäver.
            lines[1] = Capital(lines[1]);
            try{
                System.out.println("hej");
                //Skapar en instans av en gate med class.metoden
                g = (Gate) Class.forName(lines[1]).newInstance();
                //sätter namnet. Detta använder vi senare
                g.setName(lines[0]);
                //För in dom i mapen.
                map.put(g.getName(), g);

            }catch (InstantiationException e) {
                new GateException("Something went wrong instantiating the gate " + lines[0] + " on line " + index + " in the code");
            } catch (IllegalAccessException e) {
                new GateException("Something went wrong in the CreateGates-function for gate " + lines[0] + " on line " + index + " in the code");
            } catch (ClassNotFoundException e) {
                new GateException("The gate " + lines[0] + " written in the file does not exist. This error occured on line " + index);
            }
        }
    }catch (FileNotFoundException e){
        new GateException("Could not load the given file.");
    } catch (IOException e) {
        new GateException("Something went wrong while trying to read the file. (NOT filenotfoundexception)");
    } 


    //läser filen på nytt som det står i labbbeskrivningen
    try{
        //samma som ovan. Reader, string och array med strings.
        BufferedReader br = new BufferedReader(new FileReader(file));
        String l = null;
        String[] li = null;

        while((l = br.readLine()) != null){

            //as long as the line's not a comment.
            if(l.trim().charAt(0) == '*' || l.trim().charAt(0) == '/'){
                //Omd et är en kommentar, hoppa och kör loopen nästa gång direkt.
                continue;
            }else{
                //annars splitta den
                li = l.split("\\s+");
            }

            //om det är en deklarering av en signalgate så¨ska den forstätta, annars ska den sätta inputs osv som den ska.
            if(li.length == 2){
                continue;
            }else{
                Gate gate = map.get(li[0]);
                for(int i = 2; i < li.length; i++){
                    System.out.println(map.get("b"));
                    gate.setInputGate(map.get(li[i]));
                }
            }

        }
    }catch (FileNotFoundException e){
        throw new GateException("Error loading the file");
    }catch (IOException e){
        throw new GateException("Error reading the file");
    }

    return map;
}

Answer 1

TL;DR: I'd venture your problem is on lines 90, 92 and 94: you're not calling throw on these newly created exceptions.

The classes are probably never getting instantiated due to some class problem or another (fixing the above will show you), so this is caught but as mentioned will not interrupt the execution or log (probably), but will not actually add to the map. It could, of course, be something else...

As an aside, some code quality points:

• Re-use code wisely: most of that file-reading block could be extracted to a method which would make debugging (or reading) things like this much easier.
• the Capital(String s) method should usually have small 'c' (or consider the useful WordUtils.capitalizeFully)
• Always check values coming back from map.get(foo) for null.