Java - Case insensitive Map

You know keys in the java.util.HashMap are case sensitive. It means you can keep both "abc" and "ABC" as keys in the same map.

See this example.

public static void main(String[] args) {

  Map<String, String> map = new HashMap<String, String>();
  map.put("abc", "abc");
  map.put("xyz", "xyz");
  map.put("ABC", "ABC");

  System.out.println(map);
}
Output
{ABC=ABC, abc=abc, xyz=xyz}

But some times you may need to have a case insensitive map.
In such case you can use the java java.util.TreeMap, which let you to pass a Comparator to it's constructor.

See below example

public static void main(String[] args) {

  Map<String, String> map = new TreeMap<String, String>(String.CASE_INSENSITIVE_ORDER);
  map.put("abc", "abc");
  map.put("xyz", "xyz");
  map.put("ABC", "ABC");

  System.out.println(map);
}
Output
{abc=ABC, xyz=xyz}

Note:
Another option is to write your own class by extending the HashMap class and overriding the get() and put() methods.