Java HashMap的多个键具有灵活分配的多个值

Question

I have a problem with my Java Code. I want to store multiple Values in one Key but I want to store them flexible. This means I read from a textfile and every line is one word. To store them, I want to build pairs of words. For example:

word1/word2

word2/word3

word3/word4

I have changed this method a little bit. I want to store the values of the keys in an arraylist. This means everytime when a new key comes up a new Arraylist and key will be stored, but if the key is in the map I want to store them in the list of this key. Is this possible?

We have to store them in a hashmap. But I can not get it to work:

private HashMap<String, ArrayList<String>> hmap = new HashMap<String, ArrayList<String>>();

    private ArrayList<String> wort2;

    public GrammelotH(String filename) throws IOException {
        String fixWort = ".";

        BufferedReader br = new BufferedReader(new FileReader(filename));
        while (br.ready()) {
            String line = br.readLine();
            if (hmap.containsKey(fixWort)) {
                hmap.put(fixWort, wort2.add(line));
            }else {
                hmap.put(fixWort, new ArrayList<String>().add(line));
            }

            fixWort = line;
        }

        br.close();

    }

The problem is the put order. Has anybody of you an idea how to get

hmap.put(fixWort, new ArrayList<String>().add(line));

and

hmap.put(fixWort, wort2.add(line));

to work?

Thank you for your help! Bye Bye!

Answer 1

I think I'd be looking at something like

List l = hmap.get(line);
if (l != null) {
     l.add(line));
}else {
     l = new ArrayList<String>();
     l.add(line)
     hmap.put(line, l);
}

So, you see if the map already contains the line you have just read from the file. If it does, you just add it to the associated list. If it doesn's.create a list, add line to it, and then add both to the Map.