Sometimes we need to Sort Apex Map to built functionality in apex but Map do not has sorting support, they are a key value pair collection.
To Sort Apex Map we need to use wrapper class and comparable interface.
before going to the code lets know about concept of wrapper class in apex.
What is Wrapper Class :
So these are the abstract data structure by which a developer create its own data structure by groupuing another available data structure.
It expands user capablity and give more power to developer a customized application. it can be user for creating Visualforce page where page contains Boolean as check box and list item as value.
Here in this post I explain you how to sort a map by both key and values .
1) So first we are creating a map that is regionContactMap. having key as city and value as count
Map regionContactMap = new Map();
regionContactMap.put('noida',5);
regionContactMap.put('delhi',2);
regionContactMap.put('hapur',8);
regionContactMap.put('ghaziabad',7);
2) Now creating a list of type RegionWrapper and adding data to the list like below :
RegionWrapper[] regionList = new RegionWrapper[0];
for(string key: regionContactMap.keyset()) {
regionList.add(new RegionWrapper(key, regionContactMap.get(key)));
}
// sorting list in ascending order
regionList.sort();
// final list of key value pair (in descending order)
List finalList = new List();
for(Integer i = regionList.size()-1; i>=0;i–)
{
finalList.add(regionList.get(i));
}
system.debug(‘value of region list is @@@@@’+regionList);
system.debug(‘value of region list in descending order @@@@@’+finalList);
3) Creating a wrapper class named Regionwrapper that implement Comparable Interface . Wrapper class data members name should be map keys and values.
// wrapper class to sort map
public class RegionWrapper implements Comparable {
public string region;
public Integer counter;
public RegionWrapper(string region, Integer counter) {
this.region = region;
this.counter = counter;
}
public Integer compareTo(Object other) {
return counter-((RegionWrapper)other).counter;
}
}
Now here is the final code you just need to replace your map in the below code the code will return you a finalist of your sorted map.
Map regionContactMap = new Map();
regionContactMap.put('noida',5);
regionContactMap.put('delhi',2);
regionContactMap.put('hapur',8);
regionContactMap.put('ghaziabad',7);
RegionWrapper[] regionList = new RegionWrapper[0];
for(string key: regionContactMap.keyset())
{
regionList.add(new RegionWrapper(key, regionContactMap.get(key)));
}
// sorting list in ascending order
regionList.sort();
// final list of key value pair (in descending order)
List finalList = new List();
for(Integer i = regionList.size()-1; i>=0;i--)
{
finalList.add(regionList.get(i));
}
system.debug('value of region list is @@@@@'+regionList);
// here final list contains sorted map values
system.debug('value of region list in descending order @@@@@'+finalList);
// wrapper class to sort map
public class RegionWrapper implements Comparable
{
public string region;
public Integer counter;
public RegionWrapper(string region, Integer counter)
{
this.region = region;
this.counter = counter;
}
public Integer compareTo(Object other) {
// for descending order
return counter-((RegionWrapper)other).counter;
}
}
NOTE: To Sort map in ascending order replace the code in compareto like:
return ((RegionWrapper)other).counter – counter;
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very helpful and Impressive content …
Thanks for this post.