Java Complex Collection

Question

I have data in this format: (in a file)

key1:fieldname1:fieldvalue1
key1:fieldname2:fieldvalue2
key2:fieldname1:fieldvalue1

I need this to be formatted to:

{key1=[{fieldname1=fieldvalue1,fieldname2=fieldvalue2}],key2=[{fieldname1=fieldvalue1}]}

As you can see it involves Map and ArrayList. I actually need it in Map and ArrayList.

Please suggest.

Thank you

Answer 1

Find string method "split" and how to use it and also how to read text file line by line. By this, you can easily parse line by line and get what key, fieldname and fieldvalue is.

Then you can go as following for each line:

1. If key does not exist in your map, create empty array in it.

2. Add item to array specified at given key

Answer 2

Try this:

    String[] str = {"key1:fieldname1:fieldvalue1", "key1:fieldname2:fieldvalue2", "key2:fieldname1:fieldvalue1"};
    Map<String, List<String>> map = new HashMap<String, List<String>>();

    for (String s: str) {
        String[] temp = s.split(":");

        if (map.get(temp[0]) == null) {
            map.put(temp[0], new ArrayList());
        }
        map.get(temp[0]).add(temp[1] + "=" + temp[2]);
    }

This example is under the assumption that fieldname1:fieldvalue2 need to be stored as string. You can get the high level idea and then modify according to your requirements