Java Stream - Sort map by key

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In this Article , we’ll Discuss How we can Sort map by key in java 8.

We want to sort below Map by key

Sort map by Key

Map<String, Integer> map = new HashMap<>();
	map.put("Niraj", 6);
	map.put("Rahul", 43);
	map.put("Ram", 44);
	map.put("Sham", 33);
	map.put("Pratik", 5);
	map.put("Ashok", 5);

Map Sorting using comparingByKey in Ascending order

Sort map by Key Ascending order

Map<String, Integer> sortedMapByValueAscending 
          = map.entrySet()
         .stream().sorted(Map.Entry.comparingByKey())
         .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e1,LinkedHashMap::new));

Map Sorting using comparingByKey in Descending order. For Descending order you need to use reversed()

Sort map by Key Descending order

Map<String, Integer> sortedMapByValueDescending
            = map.entrySet()
            .stream().sorted(Map.Entry.<String,Integer>comparingByKey().reversed())															
            .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (e1, e2) -> e1 ,LinkedHashMap::new));

Source Code Github Link