Java中关于HashMap的使用和遍历

package com.pb.collection;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
import java.util.Map.Entry;

public class HashMapDemo {

    public static void main(String[] args) {
        
        HashMap<String, String> hashMap = new HashMap<String, String>();
        hashMap.put("cn", "中国");
        hashMap.put("jp", "日本");
        hashMap.put("fr", "法国");
        
        System.out.println(hashMap);
        System.out.println("cn:" + hashMap.get("cn"));
        System.out.println(hashMap.containsKey("cn"));
        System.out.println(hashMap.keySet());
        System.out.println(hashMap.isEmpty());
        
        hashMap.remove("cn");
        System.out.println(hashMap.containsKey("cn"));
        
        //采用Iterator遍历HashMap
        Iterator it = hashMap.keySet().iterator();
        while(it.hasNext()) {
            String key = (String)it.next();
            System.out.println("key:" + key);
            System.out.println("value:" + hashMap.get(key));
        }
        
        //遍历HashMap的另一个方法
        Set<Entry<String, String>> sets = hashMap.entrySet();
        for(Entry<String, String> entry : sets) {
            System.out.print(entry.getKey() + ", ");
            System.out.println(entry.getValue());
        }
    }
}

import java.util.Iterator;
import java.util.List;
import java.util.HashMap;
import java.util.ArrayList;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;
import java.util.Map.Entry;
/**
 * 在不创建学生类的情况下，从键盘输入n个学生信息(学号，姓名，年龄），
 * 输入完成后，打印出各个学生信息
 * @author ccna_zhang
 *
 */
public class Assignment {
    
    public static void main(String[] args) {
        
        //定义保存学生信息的List，元素类型为HashMap
        List<HashMap<String, Object>> list = new ArrayList<HashMap<String, Object>>();
        Scanner input = new Scanner(System.in);
        
        System.out.println("请输入学生的信息,y表示继续，n表示退出");
        while("y".equals(input.next())) {
            HashMap<String, Object> map = new HashMap<String, Object>();
            System.out.println("请输入学号");
            map.put("studentno", input.next());
            System.out.println("请输入姓名");
            map.put("name", input.next());
            System.out.println("请输入年龄");
            map.put("age", input.nextInt());
            list.add(map);
            System.out.println("请继续输入学生的信息,y表示继续，n表示退出");
        }
        
        System.out.println("输入的学生信息为:");
        System.out.println("学生数量为:" + list.size());
        
        Iterator<HashMap<String, Object>> it = list.iterator();
        int i = 1;
        while(it.hasNext()) {
            HashMap<String, Object> stuMap = it.next();
            System.out.print("第" + i + "个学生的信息为");
            System.out.println("学号:" + stuMap.get("studentno") + " ,姓名:" + stuMap.get("name") + " ,年龄:" + stuMap.get("age"));
        }
    }
}