Ath now :
I cannot find a simple way to find the sum of all keys within a ListMultiMap in Java.
I have a ListMultiMap:
ListMultimap<String, Long> foodCals = ArrayListMultimap.create();
That contains different keys with multiple values within them:
["19/03/2020": 77, 88, 88], ["18/03/2020": 22, 33, 21], ["17/03/2020": 77, 33, 88]
How do you find the total of each Key? And get an output like: 1-253 , 2-76, 3-198.
Something like this:
int p = 0;
for(String s : foodCals.keySet()){
System.out.Println(p + foodCals.sumOfKey(p)) //Print the index number + the sumOfKey (sumOfKey doesn't exist).
p++;
}
Mureinik :
There's no built-in function to do so, but treating the multimap as a Map (with asMap()) will give you a collection of the values per day. From there, you just need to sum them, e.g., by streaming them and converting them to primitives:
int p = 0;
for (Collection<Long> vals : foodCals.asMap().values()) {
System.out.println(p + " - " + vals.stream().mapToLong(Long::longValue).sum());
p++;
}
EDIT:
For older Java versions (before 8), the same logic should apply, although the syntax is a bit clunkier, and you'll have to sum the values yourself:
int p = 0;
for (Collection<Long> vals : foodCals.asMap().values()) {
long sum = 0L;
for (Long val : vals) {
sum += val;
}
System.out.println(p + " - " + sum);
p++;
}
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