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", "中國"); 
    hashMap.put("jp", "日本"); 
    hashMap.put("fr", "法國"); 
     
    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遍歷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)); 
    } 
     
    //遍歷HashMap的另一個方法 
    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; 
/** 
 * 在不創建學生類的情況下，從鍵盤輸入n個學生信息(學號，姓名，年齡）， 
 * 輸入完成后，打印出各個學生信息 
 * @author ccna_zhang 
 * 
 */ 
public class Assignment { 
   
  public static void main(String[] args) { 
     
    //定義保存學生信息的List，元素類型為HashMap 
    List<HashMap<String, Object>> list = new ArrayList<HashMap<String, Object>>(); 
    Scanner input = new Scanner(System.in); 
     
    System.out.println("請輸入學生的信息,y表示繼續，n表示退出"); 
    while("y".equals(input.next())) { 
      HashMap<String, Object> map = new HashMap<String, Object>(); 
      System.out.println("請輸入學號"); 
      map.put("studentno", input.next()); 
      System.out.println("請輸入姓名"); 
      map.put("name", input.next()); 
      System.out.println("請輸入年齡"); 
      map.put("age", input.nextInt()); 
      list.add(map); 
      System.out.println("請繼續輸入學生的信息,y表示繼續，n表示退出"); 
    } 
     
    System.out.println("輸入的學生信息為:"); 
    System.out.println("學生數量為:" + 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 + "個學生的信息為"); 
      System.out.println("學號:" + stuMap.get("studentno") + " ,姓名:" + stuMap.get("name") + " ,年齡:" + stuMap.get("age")); 
    } 
  } 
}