Java Program to convert a Map to a read only map

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
public class Demo {
	public static void main(String[] argv) throws Exception {
		Map<String, String>map = new HashMap<String,String>();
		map.put("1","A");
		map.put("2","B");
		map.put("3","C");
		// making it read-only
		map = Collections.unmodifiableMap(map);
		try {
		map.put("4","D");
		map.put("5","E");
		map.put("6","F");
		} catch (UnsupportedOperationException e) {
		System.out.println(e.getMessage());
		}
	}
}