如何用Java编写模拟ATM取款机的程序

import java.io.IOException;

/**
* ATM机类
*
* 查看余额
*
* 取款
*
* 存款
*
* 退出系统
*
*
*
*/

public class ATM {
static double yue = 1200.00;

public static void main(String[] arg) {
ATM localTest1 = new ATM();
localTest1.ATM_Operate();
}

/**
* ATM机的操作
*/
private void ATM_Operate() {
System.out.println("欢迎使用中国工商银行ATM取款机");
System.out.println("1、查看余额 2、取款");
System.out.println("3、存款 0、退出");
System.out.print("请输入您需要的服务:");
byte[] buffer = new byte[512];
try {
int count = System.in.read(buffer);// 返回实际读取的字节数
System.out.print("您输入的是:");
for (int i = 0; i < count; i++) {
System.out.print("" + (char) buffer[i]);
}
if ((char) buffer[0] == '1') {
// 查看余额
System.out.println("您的余额是：￥" + yue + "元");
System.out.println();
ATM_Operate();
} else if ((char) buffer[0] == '2') {
// 取款
withdrawal();
System.out.println();
ATM_Operate();
} else if ((char) buffer[0] == '3') {
// 存款
deposit();
System.out.println();
ATM_Operate();
} else if ((char) buffer[0] == '0') {
// 退出
System.out.println("您已经成功退出系统，谢谢你的使用");
System.exit(0);
} else {
System.out.println("输入不合法，请重新输入");
System.out.println();
ATM_Operate();
}

} catch (IOException e) {
e.printStackTrace();
}
}

/**
* 取款
*
* @throws IOException
*/
private void withdrawal() throws IOException {
byte[] buffer = new byte[512];

System.out.print("请输入您要取出的金额:￥");
int count2 = System.in.read(buffer);// 返回实际读取的字节数
System.out.print("您输入的金额是:");
for (int i = 0; i < count2 - 1; i++) {
System.out.print("" + (char) buffer[i]);
}
System.out.println();
// 字符0 ~ 9对应ASCII值48 ~ 57
boolean flag = false;
for (int i = 0; i < count2 - 1; i++) {
if ((char) buffer[i] > 47 && (char) buffer[i] < 58) {
if (i == count2 - 2) {
flag = true;
}
} else {
// 输入的字符不是数值
System.out.println("输入不合法，请重新输入");
withdrawal();
break;
}
}
System.out.println();
if (flag) {
System.out.print("您已成功取出￥:");
String num = "";
for (int i = 0; i < count2 - 1; i++) {
System.out.print("" + (char) buffer[i]);
num += (char) buffer[i];
}
yue -= Double.valueOf(num);
System.out.print("，现在余额￥:" + yue);

}
}

/**
* 存款
*
* @throws IOException
*/
private void deposit() throws IOException {
byte[] buffer = new byte[512];

System.out.print("请输入您要存入的金额:￥");
int count2 = System.in.read(buffer);// 返回实际读取的字节数
System.out.print("您输入的金额是:");
for (int i = 0; i < count2 - 1; i++) {
System.out.print("" + (char) buffer[i]);
}
System.out.println();
// 字符0 ~ 9对应ASCII值48 ~ 57
boolean flag = false;
for (int i = 0; i < count2 - 1; i++) {
if ((char) buffer[i] > 47 && (char) buffer[i] < 58) {
if (i == count2 - 2) {
flag = true;
}
} else {
// 输入的字符不是数值
System.out.println("输入不合法，请重新输入");
withdrawal();
break;
}
}
System.out.println();
if (flag) {
System.out.print("您已成功存入￥:");
String num = "";
for (int i = 0; i < count2 - 1; i++) {
System.out.print("" + (char) buffer[i]);
num += (char) buffer[i];
}
yue += Double.valueOf(num);
System.out.print("，现在余额￥:" + yue);

}
}
}