方法分为两类：

一类是基于map的Entry；map.entrySet();

一类是基于map的key；map.keySet()

而每一类都有两种遍历方式：

a.利用迭代器 iterator；

b.利用for-each循环；

代码举例如下

package cn.wzb;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import java.util.Set;

import java.util.Map.Entry;

//循环遍历map的方法

public class TestMap {

	public static void main(String[] args) {

		Map<String, Integer> map = new HashMap<String, Integer>();

		map.put("a", 1);

		map.put("b", 2);

		map.put("c", 3);

		// JDK1.4中

		// 遍历方法一 hashMap.entrySet() 遍历

		System.out.println("方法一");

		Iterator<Entry<String, Integer>> it = map.entrySet().iterator();

		while (it.hasNext()) {

			Map.Entry<String, Integer> entry =  it.next();

			String key = entry.getKey();

			 Integer value = entry.getValue();

			System.out.println("key = " + key + "; value = " + value);

		}

		System.out.println("");

		// JDK1.5中,应用新特性For-Each循环	// 遍历方法二

		System.out.println("方法二");

		for (Map.Entry<String, Integer> entry : map.entrySet()) {

			String key = entry.getKey();

			String value = entry.getValue().toString();

			System.out.println("key =" + key + " value = " + value);

		}

		System.out.println("");

		// 遍历方法三 hashMap.keySet().iterator() 遍历

		System.out.println("方法三");

		for (Iterator<String> i = map.keySet().iterator(); i.hasNext(); ) {

			 String key = i.next();

			System.out.println(" key = " + key + "; value = " + map.get(key));

		}

	   /*

		for (Iterator<Integer> i = map.values().iterator(); i.hasNext(); ) {

			Integer value = i.next();

			System.out.println(value));// 循环输出value

		}

		*/

		/*

		for(Integer value : map.values() ) {

			System.out.println("value = " + value);

		}

		*/

		System.out.println("");

		// 遍历方法四  Hashmap.keySet()遍历

		System.out.println("方法四");

		for (String key : map.keySet()) {

			System.out.println("key = " + key + "; value = " + map.get(key));

		}

		System.out.println();

		// java如何遍历Map <String, ArrayList> map = new HashMap <String, ArrayList<Integer> >();

		System.out.println("java  遍历Map <String, ArrayList<Integer> map = new HashMap <String, ArrayList<Integer>>();");

		System.out.println("方法一：");

		Map<String, List<Integer> > mapList  = new HashMap <String, List<Integer> >();

		List<Integer> list = new ArrayList<Integer>();

		list.add(1);

		list.add(2);

		list.add(3);

		list.add(4);

		list.add(5);

		mapList.put("aaa", list);

		mapList.put("bbb", list);

		Set<String> keys = mapList.keySet();

		Iterator<String> iterator = keys.iterator();

		while (iterator.hasNext()) {

			String key = iterator.next();

			System.out.println(key + " : ");

			List<Integer> arrayList = mapList.get(key);

			for (Integer i : arrayList) {

				System.out.print(i + ", ");

			}

			System.out.println();

		}

		System.out.println("方法二：");

		for (Map.Entry<String, List<Integer> > entry : mapList.entrySet()) {

			String key = entry.getKey();

			System.out.println(key + " : ");

			List<Integer> values = (List<Integer>) entry.getValue();

			for (Integer value : values) {

				System.out.print(value + ", ");

			}

			System.out.println();

		}

	}

}