Iterator中的next()

DBExchangeMoney类：
  1 package com.ch.test15;

import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Timestamp;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;

import com.ch.test02.Person;

/**
 * 交换A,B,C的金额
 * @author Administrator
 *
 */
public class DBExchangeMoney {
    public static void main(String[] args) throws ClassNotFoundException, SQLException {
        //定义数据库驱动器
        String DRIVER = "com.mysql.jdbc.Driver";
        //加载数据库驱动器
        Class.forName(DRIVER);
        //定义数据库的链接
        String URL = "jdbc:mysql://192.168.1.20:3306/cuihao?useUnicode=true&characterEncoding=UTF-8";
        String Users = "root";
        String Passw = "root";
        java.sql.Connection con = null;
        try {
            con = DriverManager.getConnection(URL, Users, Passw);
            con.setAutoCommit(false);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        //PreparedStatement prepStmt = null;
        Statement st = null;
        ResultSet rs = null;
        int tem = 0;
        ArrayList<MoneyDefine> list = new ArrayList<MoneyDefine>();
        try {
            //执行sql查询
            String selectStatement = "select * from Moneys";
            st = con.createStatement();
            rs = st.executeQuery(selectStatement);
            while (rs.next()) {
                String id = rs.getString("id");
                String name = rs.getString("pname");
                int moneys = rs.getInt("prices");
                String dates = rs.getString("dates");
                MoneyDefine md = new MoneyDefine(id,name,moneys,dates);
                list.add(md);
            }
            for(Iterator<MoneyDefine> iterator = list.iterator();iterator.hasNext();){
                //错误的，next()在list内，跳到下一条的下一个位置                
                //System.out.println(iterator.next().getId() +iterator.next().getName() 
                    //                   +iterator.next().getMoneys() +iterator.next().getDates());
                //用对象p接收
                MoneyDefine p = iterator.next();
                System.out.println("ID:" +p.getId() +" 姓名：" +p.getName()
                        +" 金额：" +p.getMoneys() +" 时间：" +p.getDates());
//                System.out.println(p.getMoneys());
//                System.out.println(p.getDates());
            }
        
            System.out.println("--------------------------");
            //two给one 1000; one给two 1000;
            //更新
            String exchangeMoney = "UPDATE Moneys SET prices=prices+1000 WHERE id=1";
            String exchangeMoney1 = "UPDATE Moneys SET prices=prices-1000 WHERE id=2";
            st = con.createStatement();
            tem = st.executeUpdate(exchangeMoney);
            tem = st.executeUpdate(exchangeMoney1);
            System.out.println("执行后:" +tem);
            //查询更新后的内容
            String selectStatement1 = "select * from Moneys";
            st = (Statement) con.createStatement();
            rs = st.executeQuery(selectStatement1);
            while (rs.next()) {
                String id = rs.getString("id");
                String name = rs.getString("pname");
                String moneys = rs.getString("prices");
                Date dates = rs.getTimestamp("dates");
                System.out.print("ID:" +id);
                System.out.print(" 姓名:" +name);
                System.out.print(" 金额:" +moneys);
                System.out.print(" 时间：" +dates);
                System.out.println();
            }
            System.out.println("--------------------");
        } catch (SQLException e) {
            con.rollback();
            e.printStackTrace();
        }
        //关闭
        con.commit();
        rs.close();
        st.close();
        con.close();
    }
}

MoneyDefine类：
 1 package com.ch.test15;

import java.sql.Timestamp;
import java.util.Date;

public class MoneyDefine {

    public String id;
    public String name;
    public int moneys;
    public String dates;
    
    public MoneyDefine(String id, String name, int moneys, String dates){
        this.id = id;
        this.name = name;
        this.moneys = moneys;
        this.dates = dates;
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public float getMoneys() {
        return moneys;
    }
    public void setMoneys(int moneys) {
        this.moneys = moneys;
    }
    public String getDates() {
        return dates;
    }
    public void setDates(String dates) {
        this.dates = dates;
    }
    
    
}

DBExchangeMoney类中，将从数据库取出的元素放入ArrayList中，然后再从list里取出。
这时遇到问题，当用迭代取元素时

System.out.println(iterator.next().getId() +iterator.next().getName() +iterator.next().getMoneys() +iterator.next().getDates());

执行出行错误。

修改为：

MoneyDefine p = iterator.next();
System.out.println("ID:" +p.getId() +" 姓名：" +p.getName()+" 金额：" +p.getMoneys() +" 时间：" +p.getDates());

正确输出。

如果每次都调用iterator.next()，则第一次调用iterate.next()，指向List的第一行的getId()，即id=1，第二次调用iterate.next()，就会指向第二行的getName()，即name=two。第三次调用，就会报出异常。所以无法正常输出！

id	name	prices	dates
1	one	0	2015-04-15 11:10:34
2	two	1000	2015-04-15 11:10:40

当iterator.next()应该赋值给一个对象p，然后调用对象p来取值，这样p每次会从每行的首个元素开始迭代。

JDK API 1.6，关于Iterator中next()的说明：

next()

返回迭代的下一个元素。

返回：

迭代的下一个元素。

抛出：

NoSuchElementException - 没有元素可以迭代。