1：先写一个类，包括商品的基本属性
package com.xt.java.base25;
public class Goods {
private int ID;
private String name;
private int number;
private double price;
/**
* @return the iD
*/
public int getID() {
return ID;
}
/**
* @param iD the iD to set
*/
public void setID(int iD) {
ID = iD;
}
/**
* @return the name
*/
public String getName() {
return name;
}
/**
* @param name the name to set
*/
public void setName(String name) {
this.name = name;
}
/**
* @return the number
*/
public int getNumber() {
return number;
}
/**
* @param number the number to set
*/
public void setNumber(int number) {
this.number = number;
}
/**
* @return the price
*/
public double getPrice() {
return price;
}
/**
* @param price the price to set
*/
public void setPrice(double price) {
this.price = price;
}
}
2：将数据库和Java连接起来，并写成一个单独的类，使用起来更加方便
package com.xt.java.base25;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class GoodDAO {
private Connection conn;
private Statement stat;
private String url="jdbc:mysql://localhost:3306/lyxdatabases";
private String dbDriver="com.mysql.jdbc.Driver";
private String userName="root";
private String password="1234";
//私有的构造方法，只有在本类中可以进行实例化一次，为了保护用户的隐私使用这种方法，切记！！！
private GoodDAO(){
}
private static GoodDAO gda=null;
/**
* 写一个方法，从方法中获得实例,只能实例化一次。
*/
public static GoodDAO getGoodDAO(){
if(gda==null){
gda=new GoodDAO();
}
return gda;
}
public Connection getConnection() throws Exception{
try {
Class.forName(dbDriver);
return DriverManager.getConnection(url,userName,password);
} catch (ClassNotFoundException e) {
throw new ClassNotFoundException("数据库找不到驱动！！");
} catch (SQLException e) {
throw new SQLException("数据库连接异常！！");
}
}
//关闭Connection
public void closeConnection(Connection conn){
try{
if(conn!=null){
conn.close();
}
}catch(Exception e){
System.out.println(e);
}
}
//关闭Statement
public void closeStatement(Statement stat){
try{
if(stat!=null){
stat.close();
}
}catch(Exception e){
System.out.println(e);
}
}
//关闭ResultSet
public void closeResultSet(ResultSet rs){
try{
if(rs!=null){
rs.close();
}
}catch(Exception e){
System.out.println(e);
}
}
}
3；主方法，直接实现功能
package com.xt.java.base25;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Scanner;
public class Main {
GoodDAO gDao=GoodDAO.getGoodDAO();
Connection conn;
Statement stat;
ResultSet rs;
Scanner scanner=new Scanner(System.in);
static double sumMonNum;
//显示货物清单， 清单要求包含每种商品的剩余数量。
public void showList(){
String sql="select *from autoGoods";
try {
conn=gDao.getConnection();
stat=conn.createStatement();
rs=stat.executeQuery(sql);
while(rs.next()){
System.out.println("商品编号："+rs.getString("ID"));
System.out.print("商品名称："+rs.getString("name"));
System.out.print(" 商品剩余数量："+rs.getInt("number"));
System.out.print("商品单价："+rs.getDouble("price")+"\n\n");
}
} catch (Exception e) {
e.printStackTrace();
}finally{
gDao.closeResultSet(rs);
gDao.closeStatement(stat);
gDao.closeConnection(conn);
}
}
//选择一个商品编号购买东西
public void buyGoods(){
System.out.println("请输入你要购买的商品编号：");
int buyID=scanner.nextInt();
System.out.println("请投币：");
sumMonNum=scanner.nextDouble();
System.out.println("您的商品将要出货！！！");
String sql="update autoGoods set number=(number-1) where ID='"+buyID+"'";
String sql1="select price from autoGoods where ID='"+buyID+"'";
try {
conn=gDao.getConnection();
stat=conn.createStatement();
rs=stat.executeQuery(sql1);
while(rs.next()){
sumMonNum=sumMonNum-rs.getDouble("price");
System.out.println("您的零钱为"+sumMonNum);
}
if(stat.executeUpdate(sql)>0){
System.out.println("购买成功！！");
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
gDao.closeResultSet(rs);
gDao.closeStatement(stat);
gDao.closeConnection(conn);
}
}
//询问继续的操作
public void askOpration(){
while(true){
System.out.println("--------请选择您接下来得操作-------");
System.out.println("继续购买-------1");
System.out.println("结束购买，找零-------2");
int operationNum=scanner.nextInt();
switch(operationNum){
case 1:{
System.out.println("请输入你要购买的商品编号：");
int buyID=scanner.nextInt();
System.out.println("您的商品将要出货！！！");
String sql="update autoGoods set number=(number-1) where ID='"+buyID+"'";
String sql1="select price from autoGoods where ID='"+buyID+"'";
try {
conn=gDao.getConnection();
stat=conn.createStatement();
rs=stat.executeQuery(sql1);
while(rs.next()){
sumMonNum=sumMonNum-rs.getDouble("price");
if(sumMonNum<0){
System.out.println("余额不足，请重新选择！！");
break ;
}else{
System.out.println("您的零钱为"+sumMonNum);
if(stat.executeUpdate(sql)>0){
System.out.println("购买成功！！");
}
}
}
}catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}finally{
gDao.closeStatement(stat);
gDao.closeConnection(conn);
}
break ;
}
case 2:{
System.out.println("将要为您找零，谢谢您的使用，期待您的下次光临~");
System.exit(0);
}
}
}
}
public static void main(String[] args) {
Main main=new Main();
while(true){
main.showList();
main.buyGoods();
main.askOpration();
}
}
}