HashMap<String,Integer> map = new HashMap<String,Integer>();
map.put("a", 4);
map.put("c", 6);
map.put("b", 2);
Desired output(HashMap):
c : 6
a : 4
b : 2
I haven't been able to find anything about Descending the order by value.
How can this be achieved? (Extra class not preferred)
Try this:
HashMap<String, Integer> map = new HashMap<String, Integer>();
map.put("a", 4);
map.put("c", 6);
map.put("b", 2);
Object[] a = map.entrySet().toArray();
Arrays.sort(a, new Comparator() {
public int compare(Object o1, Object o2) {
return ((Map.Entry<String, Integer>) o2).getValue()
.compareTo(((Map.Entry<String, Integer>) o1).getValue());
}
});
for (Object e : a) {
System.out.println(((Map.Entry<String, Integer>) e).getKey() + " : "
+ ((Map.Entry<String, Integer>) e).getValue());
}
output:
c : 6
a : 4
b : 2
You can't explicity sort the HashMap, but can sort the entries. Maybe something like this helps:
// not yet sorted
List<Integer> intList = new ArrayList<Integer>(map.values());
Collections.sort(intList, new Comparator<Integer>() {
public int compare(Integer o1, Integer o2) {
// for descending order
return o2 - o1;
}
});
One of the characteristics of the Hash elements is their particular speed on doing operations like adding, deleting and so on, and this is precisely because they use Hash algorhythms, which means they doesn't keep the order of elements that we know as ascendant or descendant. That means that with the Hash data structures you won't achieve what you want.
x is a reference type conforming to T: ((T)x) == x is true.
List entries = new ArrayList<Entry<String,Integer>>(hash.getEntries()); then sort that.