Map集合的遍历 - 黑马程序员技术交流社区

  Map<String, String> map = new HashMap<String,String>();
  map.put("1", "value1");
  map.put("2", "value2");
  map.put("3", "value3");

  //第一种：普遍使用，二次取值
  System.out.println("通过Map.keySet遍历key和value：");
  for (String key : map.keySet()) {
System.out.println("key= "+ key + " and value=" + map.get(key));
  }

  //第二种
  System.out.println("通过Map.entrySet使用iterator遍历key和value：");
  Iterator<Map.Entry<String, String>> it =map.entrySet().iterator();
  while (it.hasNext()) {
Map.Entry<String, String> entry = it.next();
System.out.println("key= " + entry.getKey() +" and value= " + entry.getValue());
  }

  //第三种：推荐，尤其是容量大时
  System.out.println("通过Map.entrySet遍历key和value");
  for (Map.Entry<String, String> entry : map.entrySet()) {
System.out.println("key= " + entry.getKey() +" and value= " + entry.getValue());
  }