Java – HashMap that maintains the original key / value when entering duplicate keys

Can HashMap retain its original key / value pair when entering duplicate keys?

For example, suppose I have something like this:

Map<String,String> map = new HashMap<String,String>();

map.put("username","password1");
map.put("username","password2");

I want the original key / value pair - username and password 1 to be reserved and not overwritten by username and password 2

Is that possible? If not, how can I eliminate duplicate entries and put them into the map?

Solution

As mentioned earlier, if you use Java 8, you can use putifabsent

If you are using an older java version, you can use concurrenthashmap, which has the putifabsent method

Of course, you get the extra overhead of thread safety, but you shouldn't worry if you don't write extremely performance - sensitive applications