map的三种遍历方法!

迷途d书童 发布于 2012/03/26 18:47
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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 + '}';
    }
}


原文链接:http://blog.csdn.net/liao3841054/article/details/7358161
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