java map的遍历的方法

map的遍历在java编程中经常使用，因此整理一下相关的资料，map的四种遍历方法：

import java.util.HashMap;import java.util.Iterator;import java.util.Map;import java.util.Map.Entry;import java.util.Set;public class MapTest {private Map<String, String> map;public MapTest() {map = new HashMap<String, String>();map.put("1", "aa");map.put("2", "bb");map.put("3", "cc");}// 第一种方法（传统方法）public void mapOne() {Set<String> set = map.keySet();Iterator<String> it = set.iterator();while (it.hasNext()) {String key = (String) it.next();String value = (String) map.get(key);System.out.println(key + "=" + value);}}// 第二种方法（传统方法）public void mapTwo() {Set set = map.entrySet();Iterator it = set.iterator();while (it.hasNext()) {Entry entry = (Entry) it.next();String key = (String) entry.getKey();String value = (String) entry.getValue();System.out.println(key + "=" + value);}}// 第三种方法（增强for循环方法）public void mapThree() {for (Object obj : map.keySet()) {String key = (String) obj;String value = (String) map.get(key);System.out.println(key + "=" + value);}}// 第四种方法（增强for循环方法）public void mapFour() {for (Object obj : map.entrySet()) {Entry entry = (Entry) obj;String key = (String) entry.getKey();String value = (String) entry.getValue();System.out.println(key + "=" + value);}}public static void main(String[] args) {MapTest mapTest = new MapTest();System.out.println("=====first=====");mapTest.mapOne();System.out.println("=====second=====");mapTest.mapTwo();System.out.println("=====three=====");mapTest.mapThree();System.out.println("=====four=====");mapTest.mapFour();}}