java中關于Map的三種遍歷方法詳解

更新時間：2013年06月04日 16:03:44 作者：

本篇文章是對java中關于Map的三種遍歷方法進行了詳細的分析介紹，需要的朋友參考下

map的三種遍歷方法！
集合的一個很重要的操作---遍歷，學習了三種遍歷方法，三種方法各有優(yōu)缺點~~

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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("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<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);
    }
//最常規(guī)的一種遍歷方法，最常規(guī)就是最常用的，雖然不復雜，但很重要，這是我們最熟悉的，就不多說了??！
    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進行遍歷，它的優(yōu)點在于可以根據你所想要的key值得到你想要的 values，更具靈活性?。?BR>    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));
        }
    }
　　//比較復雜的一種遍歷在這里，呵呵~~他很暴力哦，它的靈活性太強了，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 + '}';
    }
}