MapIteratorExample

/***
 *   Copyleft - incognito
 * 
 *  @author: incognito_at_wareninja
 *  @see https://github.com/WareNinja
 *  disclaimer: I code for fun, dunno what I'm coding about :)
 */

package utils;

import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * How To Iterate Through Java Map or Hashmap
 * source adapted from; 
 * 		http://tutorialswithexamples.com/how-to-iterate-through-map-or-hashmap-in-java/
 * 		http://www.sergiy.ca/how-to-iterate-over-a-map-in-java/
*/
public class MapIteratorExample {

	final String TAG = MapIteratorExample.class.getSimpleName();
	
	public static void main(String[] args) {
		
		Map<String, String> mapData = new LinkedHashMap<String, String>();
        mapData.put("key-1", "val-1");
        mapData.put("key-2", "val-2");
        mapData.put("key-3", "val-3");
        mapData.put("key-4", "val-4");
        mapData.put("key-5", "val-5");
        
        /**
         * Method #1: Using EntrySet and advanced for loop.
         * This method is not suitable for modifying the Map
         * while iterating through it.
         */
        System.out.println("Using EntrySet");
        for(Map.Entry<String, String> mapEntry : mapData.entrySet()){
            System.out.println(mapEntry.getKey() +" :: "+ mapEntry.getValue());
            //if you uncomment below code, it will throw java.util.ConcurrentModificationException
            //mapData.remove("key-1");
        }
 
        /**
         * Method #2: Using KeySet and advanced for loop.
         * This method is not suitable for modifying the Map
         * while iterating through it.
         */
        System.out.println("Using KeySet");
        for(String key: mapData.keySet()){
            System.out.println(key  +" :: "+ mapData.get(key));
            //if you uncomment below code, it will throw java.util.ConcurrentModificationException
            //mapData.remove("key-1");
        }
 
        /**
         * Method #3: Using Iterator and while loop.
         * In this method you can remove the entries
         * while iterating through it.
         */
        System.out.println("Using Iterator");
        Iterator<Map.Entry<String, String>> iterator = mapData.entrySet().iterator() ;
        while(iterator.hasNext()){
            Map.Entry<String, String> mapEntry = iterator.next();
            System.out.println(mapEntry.getKey() +" :: "+ mapEntry.getValue());
            //You can remove elements while iterating.
            iterator.remove();
        }
        
        /**
         * Method #4: Iterating over keys and searching for values 
         * (inefficient-slow).
         * 
         */
        System.out.println("Using KeySet (alt.2)");
        for (String key : mapData.keySet()) {
            String value = mapData.get(key);
            System.out.println("Key = " + key + ", Value = " + value);
        }
	}
}