Lowercase all HashMap keys

Question

I \'ve run into a scenario where I want to lowercase all the keys of a HashMap (don\'t ask why, I just have to do this). The HashMap has some millions of entries.

At fir

Answer 1

Instead of using HashMap, you could try using a TreeMap with case-insensitive ordering. This would avoid the need to create a lower-case version of each key:

Map map = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
map.putAll(myMap);

Once you've constructed this map, put() and get() will behave case-insensitively, so you can save and fetch values using all-lowercase keys. Iterating over keys will return them in their original, possibly upper-case forms.

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