CaseInsensitiveMap

How to ignore case sensitivity when searching a key in the java.util.Map?

There are multiple ways to achieve this

(1) We can use a TreeMap instead of HashMap, then specify a Comparator with a case insensitive order (String.CASE_INSENSITIVE_ORDER)

package in.softcaretech;

import java.util.Map;
import java.util.TreeMap;

public class TreeMapDemo {
public static void main (String args[]){
	Map<String, String> studentMap = new TreeMap<String, String>(String.CASE_INSENSITIVE_ORDER);
	
	studentMap.put("Amit", "Audi");
	studentMap.put("Nilesh", "BMW");		
	
	System.out.println("Searchnig AMIT Key from map:" + studentMap.get("AMIT"));
	System.out.println("Searchnig amit Key from map:" + studentMap.get("amit"));
  }
}

(2) You can write a wrapper map class with custom put and get methods (converting keys to lower case order).

package in.softcaretech;

import java.util.HashMap;

public class CustomMap extends HashMap<String, String>{

	    @Override
	    public String put(String key, String value) {
	       return super.put(key.toLowerCase(), value);
	    }

	    // not @Override because that would require the key parameter to be of type Object
	    public String get(String key) {
	       return super.get(key.toLowerCase());
	    }
}

package in.softcaretech;
import java.util.Map;
public class CustomMaptest {
public static void main(String[] args) {
CustomMap studentMap = new CustomMap();
studentMap.put("Amit", "Audi");
studentMap.put("Nilesh", "BMW");

System.out.println("Searchnig AMIT Key from map:" + studentMap.get("AMIT"));
System.out.println("Searchnig amit Key from map:" + studentMap.get("amit"));
    }
}

 
(3) You can use apache collections package (org.apache.commons.collections.map.CaseInsensitiveMap): 

You need to download jar file from apache website and add it to project class path, if you are using maven based project than add dependency as below 

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-collections4 -->
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-collections4</artifactId>
    <version>4.1</version>
</dependency>

package in.softcaretech;

import java.util.Map;

import org.apache.commons.collections4.map.CaseInsensitiveMap;

public class CaseInsensitiveMapDemo {
	public static void main (String args[]){

	Map<String,String> studentMap = new CaseInsensitiveMap<String,String>();
	
	studentMap.put("Amit", "Audi");
	studentMap.put("Nilesh", "BMW");		
	
	System.out.println("Searchnig AMIT Key from map:" + studentMap.get("AMIT"));
	System.out.println("Searchnig amit Key from map:" + studentMap.get("amit"));
	}
}

There might be other ways ... Suggestions and comments are welcome.