Prior to Java 8, a Map could be sorted as explained in this article :
How to sort a Map in Java

The below examples demonstrate how we can sort a map in Java 8 using lambda expression and streams. These examples use a Map where country name is key and the name of its capital is the corresponding value.
 

Sort a Map by key in Java 8

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

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}

Sort a Map by value in Java 8

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

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}

Sort a Map by key in reverse order

For sorting a map in reverse order, use Collections.reverseOrder() as shown below :

Output:

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

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

Sort a Map by key in reverse order

Similar to sorting by keys in reverse order, we can use Collections.reverseOrder() to sort the map in reverse order of values.

Output:

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

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

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