Java HashMap 반복문(loop)

 

* Java HashMap for, loop, foreach, hasnext, keyset

 

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
 
public class HashMapLoop {
    public static void main(String[] agrs) {

      HashMap<String, String> target = new HashMap<String, String>();

      target.put("키 - 1", "값:1");
      target.put("키 - 2", "값:2");
      target.put("키 - 3", "값:3");

      System.out.println("----------1----------");
      //1번 : Java 1.8부터 가능
      target.forEach((key, value)->{
          System.out.println( String.format("키 -> %s, 값 -> %s", key, value) );
      });
      
      
      System.out.println("----------2----------");
      //2번
      Iterator<String> keys = target.keySet().iterator();
      while( keys.hasNext() ){
          String key = keys.next();
          System.out.println( String.format("키 -> %s, 값 -> %s", key, target.get(key)) );
      }

      System.out.println("----------3----------");
      //3번
      for( Map.Entry<String, String> elem : target.entrySet() ){
          System.out.println( String.format("키 -> %s, 값 -> %s", elem.getKey(), elem.getValue()) );
      }

      System.out.println("----------4----------");
      //4번
      for( String key : target.keySet() ){
          System.out.println( String.format("키 -> %s, 값 -> %s", key, target.get(key)) );
      }

    }
}