map的三种遍历方法

　　集合的一个很重要的操作---遍历，学习了三种遍历方法，三种方法各有优缺点~~

/* * To change this template, choose Tools | Templates * and open the template in the editor. */package cn.tsp2c.liubao;import java.util.Collection;import java.util.HashMap;import java.util.Iterator;import java.util.Map;import java.util.Set;import java.util.TreeMap;/** * * @author Administrator */public class TestMap {    public static void main(String[] args) {        Map<String, Student> map = new HashMap<String, Student>();        Student s1 = new Student("宋江", "1001", 38);        Student s2 = new Student("卢俊义", "1002", 35);        Student s3 = new Student("吴用", "1003", 34);               map.put("1001", s1);        map.put("1002", s2);        map.put("1003", s3);        Map<String, Student> subMap = new HashMap<String, Student>();        subMap.put("1008", new Student("tom", "1008", 12));        subMap.put("1009", new Student("jerry", "1009", 10));        map.putAll(subMap);        work(map);        workByKeySet(map);        workByEntry(map);    }　　//最常规的一种遍历方法，最常规就是最常用的，虽然不复杂，但很重要，这是我们最熟悉的，就不多说了！！    public static void work(Map<String, Student> map) {        Collection<Student> c = map.values();        Iterator it = c.iterator();        for (; it.hasNext();) {            System.out.println(it.next());        }    }　　//利用keyset进行遍历，它的优点在于可以根据你所想要的key值得到你想要的 values，更具灵活性！！    public static void workByKeySet(Map<String, Student> map) {        Set<String> key = map.keySet();        for (Iterator it = key.iterator(); it.hasNext();) {            String s = (String) it.next();            System.out.println(map.get(s));        }    }　　//比较复杂的一种遍历在这里，呵呵~~他很暴力哦，它的灵活性太强了，想得到什么就能得到什么~~    public static void workByEntry(Map<String, Student> map) {        Set<Map.Entry<String, Student>> set = map.entrySet();        for (Iterator<Map.Entry<String, Student>> it = set.iterator(); it.hasNext();) {            Map.Entry<String, Student> entry = (Map.Entry<String, Student>) it.next();            System.out.println(entry.getKey() + "--->" + entry.getValue());        }    }}class Student {    private String name;    private String id;    private int age;    public Student(String name, String id, int age) {        this.name = name;        this.id = id;        this.age = age;    }    @Override    public String toString() {        return "Student{" + "name=" + name + "id=" + id + "age=" + age + '}';    }}

转自：http://www.cnblogs.com/christ/archive/2010/10/30/1865134.html