Map.Entry 遍历之泛型

来源：互联网发布：mac mini 电源线编辑：程序博客网时间：2024/05/21 00:00

上一遍文档讲到Map.Entry的遍历map方法，但没有使用泛型，导致每次遍历获取元素时要强制转换。下面看一版使用泛型的代码示例

import java.util.*;public class AnswerTo19{public static void main(String args[]){List<Account> list = new ArrayList<Account>(); Map<Long,Account> map=new HashMap<Long,Account>();list.add(new Account(10.00,"1234")); list.add(new Account(15.00,"5678")); list.add(new Account(1000,"1010"));//list容器添加3个Account对象Iterator<Account> itor=list.iterator();//遍历list元素while(itor.hasNext()){Account acc=itor.next();Long ID=acc.getId();map.put(ID,acc);//将遍历的list对象的ID和对象分别加入到MAP map中}Set<Map.Entry<Long,Account>> set=map.entrySet();//获取map的映射关系键值对set集合，类型为 Map.Entry 指明获取对象类型Iterator<Map.Entry<Long,Account>> itor2=set.iterator();//指明遍历的元素的类型while(itor2.hasNext()){Map.Entry<Long,Account> me=(Map.Entry<Long,Account>)itor2.next();//遍历set集合中的元素long Id=me.getKey().longValue();//通过遍历元素的getKey()和getValue()获得键值对的 键和值Account act=me.getValue();//前面已指明类型，此处无需转换double balance=act.getBalance();<span style="font-family: Arial, Helvetica, sans-serif;">//前面已指明类型，此处无需转换</span>System.out.println("ID="+Id+" "+"balance="+balance);}}}class Account{long id;double balance;String password;public Account(double balance,String password){this.id=(long)(Math.random()*100);this.balance=balance;this.password=password;}public long getId(){return id;}public double getBalance(){return balance;}public String getPassword(){return password;}public boolean equals(Object obj){if(obj instanceof Account){Account ao = (Account)obj;return (id==ao.getId())&&(password==ao.getPassword())&&(balance==ao.getBalance());}else return super.equals(obj);}public int hashCode(){return password.hashCode();}}

运行结果：

ID=37 balance=15.0
ID=23 balance=10.0
ID=12 balance=1000.0

0 0