StaticInitialization.java

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

// There's more than one way to do it
public class StaticInitialization {

    private static final Map<String, String> MAP_ONE = new HashMap<String, String>() {{
            put("one",   "1. first");
        }};
    
    private static final Map<String, String> MAP_TWO = new HashMap<String, String>();
    
    private static final Map<String, String> MAP_THREE;

    private static final Map<String, String> MAP_FOUR;

    private static final Map<String, String> MAP_FIVE = createMapFive();

    static {        

        // Initialize MAP_TWO
        MAP_TWO.put("one",   "2. first");
        MAP_TWO.put("two",   "2. second");

        // Initialize MAP_THREE
        Map<String, String> map = new HashMap<String, String>();
        map.put("one",   "3. first");
        map.put("two",   "3. second");
        map.put("three", "3. third");

        MAP_THREE = Collections.unmodifiableMap(map);

        // Initialize MAP_FOUR
        MAP_FOUR = Collections.unmodifiableMap(new HashMap<String, String>() {{
                    put("one",   "4. first");
                    put("two",   "4. second");
                    put("three", "4. third");
                    put("four",  "4. fourth");
                }});

    }

    private static Map<String, String> createMapFive() {
        return Collections.unmodifiableMap(new HashMap<String, String>() {{
                    put("one",   "5. first");
                    put("two",   "5. second");
                    put("three", "5. third");
                    put("four",  "5. fourth");
                    put("five",  "5. fifth");
                }});
    }

    public static void main(String[] args) {
        System.out.println(MAP_ONE.get("one"));
        System.out.println(MAP_TWO.get("two"));
        System.out.println(MAP_THREE.get("three"));
        System.out.println(MAP_FOUR.get("four"));
        System.out.println(MAP_FIVE.get("five"));

        System.out.println("---------");
        
        MAP_ONE.put("one",   "1) First");
        MAP_TWO.put("two",   "2) Second");

        try { MAP_THREE.put("three", "3) Third"); } catch (Exception e) { }
        try { MAP_FOUR.put("four",   "4) Fourth"); } catch (Exception e) { }
        try { MAP_FIVE.put("five",   "5) Fifth"); } catch (Exception e) { }

        System.out.println(MAP_ONE.get("one"));
        System.out.println(MAP_TWO.get("two"));
        System.out.println(MAP_THREE.get("three"));
        System.out.println(MAP_FOUR.get("four"));
        System.out.println(MAP_FIVE.get("five"));

    }
}