集合中的三種遍歷方式，如下代碼：

import java.util.Collection;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

import java.util.TreeMap;

public class TestMap {

public static void main(String[] args) {

Map map = new HashMap();

Student s1 = new Student("宋江", "1001", 38);

Student s2 = new Student("盧俊義", "1002", 35);

Student s3 = new Student("吳用", "1003", 34);

map.put("1001", s1);

map.put("1002", s2);

map.put("1003", s3);

Map subMap = new HashMap();

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);

}

//第一種方式

public static void work(Map map) {

Collection c = map.values();

Iterator it = c.iterator();

for (; it.hasNext();) {

System.out.println(it.next());

}

}

//第二種方式

public static void workByKeySet(Map map) {

Set key = map.keySet();

for (Iterator it = key.iterator(); it.hasNext();) {

String s = (String) it.next();

System.out.println(map.get(s));

}

}

//第三種方式

public static void workByEntry(Map map) {

Set> set = map.entrySet();

for (Iterator> it = set.iterator(); it.hasNext();) {

Map.Entry entry = (Map.Entry) 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 + '}';

}