How to sort a HashMap in Java [duplicate]

Answer 1

In Java 8:

Comparator> valueComparator = 
    (e1, e2) -> e1.getValue().getField().compareTo(e2.getValue().getField());

Map sortedMap = 
    unsortedMap.entrySet().stream().
    sorted(valueComparator).
    collect(Collectors.toMap(Entry::getKey, Entry::getValue,
                             (e1, e2) -> e1, LinkedHashMap::new));

Using Guava:

Map map = ...;
Function getField = new Function() {
    public Integer apply(Item item) {
        return item.getField(); // the field to sort on
    }
};
comparatorFunction = Functions.compose(getField, Functions.forMap(map));
comparator = Ordering.natural().onResultOf(comparatorFunction);
Map sortedMap = ImmutableSortedMap.copyOf(map, comparator);