1、数据表
2、DBconnection类(连接数据库)
package LESSON5; import java.sql.*; public class DBconnection { private String driver="com.mysql.jdbc.Driver";//驱动程序名 private String url="jdbc:mysql://localhost:3306/db_demo?useUnicode=true&characterEncoding=utf8"; private String user="root";//MySQL配置时的用户名 private String password="123456";//MySQL配置时的密码 public Connection getConnection(){ Connection con=null; try { Class.forName(driver); } catch (ClassNotFoundException e) { e.printStackTrace(); } try { con=DriverManager.getConnection(url, user, password); } catch (SQLException e) { e.printStackTrace(); } return con; } } 3、测试类
package LESSON5; import java.util.*; import java.sql.*; class Account{ public float show(String name) throws Exception{//显示余额 DBconnection dbconnection=new DBconnection(); Connection conn=dbconnection.getConnection(); String sql = "select * from users where username='"+name+"' "; Statement statement; statement = conn.createStatement(); ResultSet rs=statement.executeQuery(sql); String username=null; String accountid=null; float ba=0; //System.out.println("用户名"+"\t"+"账户"+"\t"+"账户余额"); while(rs.next()){ accountid=rs.getString("accountid"); ba=rs.getFloat("balance"); System.out.println("账户"+"\t\t "+"余额"); System.out.println(accountid+"\t"+ba); } return ba;//返回新的账户余额供下一次存取款操作使用 } public void deposit(float amount,float balance,String username)throws Exception{//存款 float NewBalance=amount+balance; DBconnection dbconnection=new DBconnection(); Connection conn=dbconnection.getConnection(); int i=0; String sql="update users set balance=? where username=?" ;//注意要有where条件 PreparedStatement preStmt =conn.prepareStatement(sql); preStmt.setFloat(1, NewBalance); preStmt.setString(2,username); preStmt.executeUpdate(); } public void withdraw(float amount,float balance,String username)throws Exception{//取款 if(amount<=balance){ float NewBalance=balance-amount; DBconnection dbconnection=new DBconnection(); Connection conn=dbconnection.getConnection(); int i=0; String sql="update users set balance=? where username=?" ;//注意要有where条件 PreparedStatement preStmt =conn.prepareStatement(sql); preStmt.setFloat(1, NewBalance); preStmt.setString(2,username); preStmt.executeUpdate(); } else{ System.out.println("余额不足"); } } } public class exercise3 { public static void main(String[] args) throws Exception { System.out.println("欢迎来到XX银行自助服务终端"); DBconnection dbconnection=new DBconnection(); Account account=new Account(); Scanner sc=new Scanner(System.in); int num=3; while(true){ System.out.println("请输入用户名"); String name=sc.nextLine(); System.out.println("请输入密码"); String p=sc.nextLine(); String sql = "select * from users where username='"+name+"'and password='"+p+"'"; Connection conn=dbconnection.getConnection(); Statement statement = conn.createStatement(); ResultSet rs=statement.executeQuery(sql);//ResultSet类，用于存放获取的结果集 String username=null; String accountid=null; float ba=0; if(rs.next()){ username=rs.getString("username"); accountid=rs.getString("accountid"); ba=rs.getFloat("balance"); System.out.println("欢迎您,"+username); System.out.println("账户"+"\t\t "+"余额"); System.out.println(accountid+"\t"+ba); rs.close(); conn.close(); while(true){ System.out.println("请输入要执行的操作：1 存款 2取款 3查询余额 4退出"); int i=sc.nextInt(); if(i==1){ System.out.println("请输入存款金额"); float amount1=sc.nextFloat(); account.deposit(amount1,ba,username); ba=account.show(username); }else if(i==2){ System.out.println("请输入取款金额"); float amount2=sc.nextFloat(); account.withdraw(amount2,ba,username); ba=account.show(username); }else if(i==3){ account.show(username); } else if(i==4){ System.exit(0); } else{ System.out.println("输入错误"); } } } else{ num--; if(num==0){ System.out.println("您的账户已冻结"); break; } System.out.println("账号或密码错误,您还有"+num+"次机会."); } } } } 4、运行结果
