举出几种 HashMap 的迭代方式

HashMap<String, String> emails = new HashMap<String, String>(); //方法一: 用entrySet()  Iterator it = emails.entrySet().iterator();  while(it.hasNext()){ Map.Entry m=(Map.Entry)it.next(); System.out.println("email-" + m.getKey() + ":" + m.getValue());  }  // 方法二：直接再循环中  for (Map.Entry<String, String> m : emails.entrySet()) {  System.out.println("email-" + m.getKey() + ":" + m.getValue()); }  // 方法三：用keySet()  Iterator it = emails.keySet().iterator();  while (it.hasNext()){ String key=(String)it.next(); System.out.println("email-" + key + ":" + emails.get(key));