java中遍历HashMap的方法

Java中，通常有两种遍历HashMap的方法，如下：

import java.util.*;public class MapTest {static HashMap<String, Integer> hashMap = new HashMap<String, Integer>();public static void main(String [] args) {hashMap.put("one", 1);hashMap.put("two", 2);hashMap.put("three", 3);hashMap.put("four", 4);hashMap.put("five", 5);Iterator iter = hashMap.entrySet().iterator();// the first method to travel the mapwhile (iter.hasNext()) {Map.Entry<String, Integer> entry = (Map.Entry<String, Integer>) iter.next();String key = entry.getKey();Integer value = entry.getValue();System.out.println(key + " " + value);}iter = hashMap.keySet().iterator();// the second method to travel the mapwhile (iter.hasNext()) {String key = (String) iter.next();Integer value = hashMap.get(key);System.out.println(key + " " + value);}} // close main()}

第一种效率要高于第二种，应尽量使用第一种进行遍历。