How to check for key in a Map irrespective of the case? [duplicate]

Answer 1

There's a CaseInsensitiveMap class in Apache commons

http://commons.apache.org/collections/

Answer 2

The easiest way is to fold the keys yourself when inserting them and looking them up. I.e.

map.put(key.toLowerCase(), value);

and

map.get(key.toLowerCase());

You could subclass e.g. HashMap to get your own class with these, if you want this automatically done.

Answer 3

create your own wrapper of string class, implement equals and hashcode, use this as the key in the hashmap:

   class MyStringKey
   {
      private String string;
      public String getString()
      {
         return string;
      }
      public void setString(String string)
      {
         this.string = string;
      }

      public boolean equals(Object o)
      {
         return o instanceof MyStringKey && this.equalsIgnoreCase(((MyStringKey)o).getString());
      }

      public boolean hashCode()
      {
         return string.toLowerCase().hashcode(); //STRING and string may not have same hashcode
      }
   }