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Java 8- Sorting a hashmap (by key and by value) using lambda expression and streams


Sometimes while working on business problems, it’s very common to come across use cases wherein a map needs to be sorted by either keys or by values. In this post, we will cover some of the examples to sort a map of primitives and custom objects. 
In below approaches, we will not destroy existing map and will create a new map to ensure consistency of sorting

1. Sort HashMap by key 
In order to sort a map by key, all we need to do is to use sorted method of stream interface and pass a default default/custom comparator to it. Moreover, to sort by keys, we need to use comparingByKey method of Entry interface of Map.

2. Sort HashMap by values 
In order to sort a map by key, all we need to do is to use sorted method of stream interface and pass a default default/custom comparator to it. Moreover, to sort by keys, we need to use comparingByValue method of Entry interface of Map.

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