遍历集合

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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 + '}';
    }
}


1.对 set 的遍历  
2. 
3.1.迭代遍历：  
4.Set<String> set = new HashSet<String>();  
5.Iterator<String> it = set.iterator();  
6.while (it.hasNext()) {  
7.  String str = it.next();  
8.  System.out.println(str);  
9.}  
10. 
11.2.for循环遍历：  
12.for (String str : set) {  
13.      System.out.println(str);  
14.}  
15. 
16. 
17.优点还体现在泛型 假如 set中存放的是Object  
18. 
19.Set<Object> set = new HashSet<Object>();  
20.for循环遍历：  
21.for (Object obj: set) {  
22.      if(obj instanceof Integer){  
23.                int aa= (Integer)obj;  
24.             }else if(obj instanceof String){  
25.               String aa = (String)obj  
26.             }  
27.              ........  
28.}