main-Map 4가지

package com.mkyong;
 
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
 
public class LoopMap {
 
public static void main(String[] args) {
 
  // initial a Map
  Map<String, String> map = new HashMap<String, String>();
  map.put("1", "Jan");
  map.put("2", "Feb");
  map.put("3", "Mar");
  map.put("4", "Apr");
  map.put("5", "May");
  map.put("6", "Jun");
 
  // Map -> Set -> Iterator -> Map.Entry -> troublesome, not recommend!
  System.out.println("\nExample 1...");
  Iterator<Entry<String,String>> iterator = map.entrySet().iterator();
  while (iterator.hasNext()) {
      Map.Entry<String,String> entry = (Map.Entry<String,String>) iterator.next();
      System.out.println("Key : " + entry.getKey() + " Value :" + entry.getValue());
  }
 
  // more elegant way, this should be the standard way, recommend!
  System.out.println("\nExample 2...");
  for (Map.Entry<String, String> entry : map.entrySet()) {
  System.out.println("Key : " + entry.getKey() + " Value : " + entry.getValue());
  }
 
  // weired, but works anyway, not recommend!
  System.out.println("\nExample 3...");
  for (Object key : map.keySet()) {
  System.out.println("Key : " + key.toString() + " Value : " + map.get(key));
  }
 
  //Java 8 only, forEach and Lambda. recommend!
  System.out.println("\nExample 4...");
  map.forEach((k,v)->System.out.println("Key : " + k + " Value : " + v));
}
 
}