Java Collection - 如何使用Iterator循环遍历Map键集

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

public class Main {
  public static void main(String[] args) {
    Map errors = new HashMap();

    errors.put("404", "A.");
    errors.put("403", "B.");
    errors.put("500", "C.");

    String errorDesc = (String) errors.get("404");
    System.out.println("Error 404: " + errorDesc);

    Iterator iterator = errors.keySet().iterator();
    while (iterator.hasNext()) {
      String key = (String) iterator.next();
      System.out.println("Error " + key + " means " + errors.get(key));
    }
  }
}