Convert a string to map with duplication

string_to_map.java

/*
 *  How to convert a string: "name1:prop1,name1:prop2,name2:prop3" to a map of the following form:
 *  {name1=[prop1, prop2], name2=[prop3]}
 */
// Before Java 8
String[] tokens = line.split(",");
Map<String, List<String>> map = new HashMap<>();
for(String token : tokens) {
    String[] pair = token.split(":");
    List<String> list = map.get(pair[1]);
    if(list == null) {
        list = new ArrayList<>();
    }

    list.add(pair[0]);
    map.put(pair[1], list);
}

// Using Java 8 Stream API
Map<String, List<String>> result = Arrays.stream(line.split(","))
        .map(s -> s.split(":"))
        .collect(groupingBy(pair -> pair[1], mapping(pair -> pair[0], toList())));