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How to count the number of occurrences of elements present in a List
Hi All,
Does anyone have any idea to how to count the number of occurrences of all the elements present in a list ? For Example, I have a list of names.
Does anyone have any idea to how to count the number of occurrences of all the elements present in a list ? For Example, I have a list of names.
List is having 10 elements with values {A,B,C,D,A,B,A,A,A,A}. Now here A came 6 times, B came 2 times , C came 1 time and D also 1 time. But I don't know how to do it in apex.
Please help how can I get the count of repeated values in apex.
The first thing that comes to mind is if you were to use a map and loop through your array.
List<String> nameArray = new List<String>{'A','B','C','D','A','B','A','A','A','A'};
Map<String,Integer> elCount = new Map<String,Integer>();
for(String key : nameArray)
{
if(!elCount.containsKey(key)){
elCount.put(key,0);
}
Integer currentInt=elCount.get(key)+1;
elCount.put(key,currentInt);
}
The result of this would look like:
{A=6, B=2, C=1, D=1}
If you are getting the names through a soql query you can use an AggregateResult List like this:
List<AggregateResult> ar = [Select Name, Count(Id) From SkinnyBeeCoding__Training_Seats__c Group By Name];
The result of this in my case is:
AggregateResult:{Name=Infantry July, expr0=6}, AggregateResult:{Name=Infantry June, expr0=1}
All Answers
The first thing that comes to mind is if you were to use a map and loop through your array.
List<String> nameArray = new List<String>{'A','B','C','D','A','B','A','A','A','A'};
Map<String,Integer> elCount = new Map<String,Integer>();
for(String key : nameArray)
{
if(!elCount.containsKey(key)){
elCount.put(key,0);
}
Integer currentInt=elCount.get(key)+1;
elCount.put(key,currentInt);
}
The result of this would look like:
{A=6, B=2, C=1, D=1}
If you are getting the names through a soql query you can use an AggregateResult List like this:
List<AggregateResult> ar = [Select Name, Count(Id) From SkinnyBeeCoding__Training_Seats__c Group By Name];
The result of this in my case is:
AggregateResult:{Name=Infantry July, expr0=6}, AggregateResult:{Name=Infantry June, expr0=1}
2) iterate through the set and take the list wih 10 elements as inner for loop.
3) compare each element of set with the list element and prepare a map<string,integer> where you store the count of respective elment.
sample code
//prepare set from the list.
Set<String> strSet = new Set<String>();
List<String> strList = new List<String>{A,B,C,D,A,B,A,A,A,A}
for(String str: strList ){
strSet.add(str);
}
//Map
Map<String, Integer> myMap = Map<String,Integer>();
//iterate through set
for(String str: strSet){
Integer countofChar = 0;
for(String strl: strList ){
if(str == str1){
countofChar++;
}
}
myMap.put(strl, countofChar);
}
System.debug(myMap);
Count Account with Different Industry(on account picklist fields is there)(e,g. For Industry Electronics we have 3 Accounts) using Map.
plz help me i am new in apex collection.