how to get the size of array inside a hashmap in java

Question

I have a new ArrayList inside a HashMap, but i don't know how to calculate the size of ArrayList inside the HashMap

Map<String, List<fruit>> groupbyregion = new HashMap<>();
for (fruit s : ll) {
    if (!groupbyregion.containsKey(s.getRegionName())) {
        groupbyregion.put(s.getRegionName(), new ArrayList<>());
    }
    groupbyregion.get(s.getRegionName()).add(s);
}
System.out.println("Group by region: " + groupbyregion);

Hint: read about Java naming conventions. Class names go UpperCase. Variable names should go camelCase. Always. — GhostCat, Nov 14 '17 at 12:37
groupbyregion.get(s.getRegionName()).size() which goes upto end i want to print only once at last iteration — Dhanasekaran Don, Nov 14 '17 at 13:03

score 3 · Accepted Answer · answered Nov 14 '17 at 12:36

3

You are already using:

groupbyregion.get(s.getRegionName()).add(s);

This calls the add() method of the ArrayList in that map slot. Thus:

groupbyregion.get(s.getRegionName()).size();

gives you the size.

Beyond that: you want to look here for how to create lists within maps in more elegant (java8) ways.

answered Nov 14 '17 at 12:36

GhostCat

137,827
25
176
248

groupbyregion.get(s.getRegionName()).size() which goes upto end i want to print only once at last iteration – Dhanasekaran Don Nov 14 '17 at 13:03
See your title: *how to get the size of array inside a hashmap in java*. This is exactly what this answer answers. – achAmháin Nov 14 '17 at 13:15

how to get the size of array inside a hashmap in java

1 Answers1