The below examples use a Map where country name is key and the name of its capital is the corresponding value.

Here, we will discuss both :

– Sort Map by key
– Sort Map by value

If you are using Java8, refer this article instead:
Sort a Map in Java 8

Sort a Map by key

Example 1: Using TreeMap

This example sorts the countryCapitalMap in ascending order of keys(country names) using a TreeMap.

Output:

Original Map :
{guyana=georgetown, japan=tokyo, nepal=kathmandu, australia=canberra, india=new delhi}

Map sorted by key :
{australia=canberra, guyana=georgetown, india=new delhi, japan=tokyo, nepal=kathmandu}
 

However, this solution may not work if you have multiple keys mapping to the same value. The next approach is more preferable.

Example 2 : Using Comparator

Output:

Original Map :
{guyana=georgetown, japan=tokyo, nepal=kathmandu, australia=canberra, india=new delhi}

Map sorted by key :
{australia=canberra, guyana=georgetown, india=new delhi, japan=tokyo, nepal=kathmandu}

If you want the map sorted in reverse(descending) order of keys, just change the compare() in Comparator accordingly :

Sort a Map by value

This example sorts the countryCapitalMap in ascending order of values(country capitals).

Output:

Original Map :
{guyana=georgetown, japan=tokyo, nepal=kathmandu, australia=canberra, india=new delhi}

Map sorted by value :
{australia=canberra, guyana=georgetown, nepal=kathmandu, india=new delhi, japan=tokyo}
 

If you are using Java8, refer this article instead:

Sort a Map in Java 8

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