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我正在设计一个假设为ATM机的课程项目。该项目的参数有5个方法和一个主程序。一切似乎都运转良好，但经过进一步测试并存入更多资金后，新的余额变成了一个约有16位小数的数字。我没有使用任何除法和方法是简单的加减算术。如何确保我的双重输出只有2个小数位？
这基本上是我得到了一些存款后。
Enter the number for one of the following choices.
1. Display Balance
2. Deposit
3. Withdraw
4. Log Out
2
Enter the amount you wish to deposit: $ 222.22
$ 2943.48
Enter the number for one of the following choices.
1. Display Balance
2. Deposit
3. Withdraw
4. Log Out
2
Enter the amount you wish to deposit: $ 333.22
$ 3276.7
Enter the number for one of the following choices.
1. Display Balance
2. Deposit
3. Withdraw
4. Log Out
2
Enter the amount you wish to deposit: $ 222.33
$ 3499.0299999999997
Enter the number for one of the following choices.
1. Display Balance
2. Deposit
3. Withdraw
4. Log Out
这是我现在的代码和我所做的。谢谢您的帮助。
import java.util.Scanner;
public class ATM {
public static Scanner keyboard = new Scanner(System.in);
// The checkID method determines if acctNum is a valid account number
// and pwd is the correct password for the account. If the account information
// is valid, the method returns the current account balance, as a string.
// If the account information is invalid, the method returns the string "error".
public static String checkID(String acctNum, String pwd)
{
String result = "error";
// Strings a, b, and c contain the valid account numbers and passwords.
// For each string, the account number is listed first, followed by
// a space, followed by the password for the account, followed by a space,
// followed by the current balance.
String a = "44567-5 mypassword 520.36";
String b = "1234567-6 anotherpassword 48.20";
String c = "4321-0 betterpassword 96.74";
if (acctNum.equals(a.substring(0, a.indexOf(" "))) &&
pwd.equals(a.substring(a.indexOf(" ")+1,a.lastIndexOf(" "))))
return result = a.substring(a.lastIndexOf(" ") + 1);
if (acctNum.equals(b.substring(0, b.indexOf(" "))) &&
pwd.equals(b.substring(b.indexOf(" ")+1,b.lastIndexOf(" "))))
return result = b.substring(b.lastIndexOf(" ") + 1);
if (acctNum.equals(c.substring(0, c.indexOf(" "))) &&
pwd.equals(c.substring(c.indexOf(" ") + 1,c.lastIndexOf(" "))))
return result = c.substring(c.lastIndexOf(" ") + 1);
return result;
}
public static int menu()
{
int menuChoice;
do
{
System.out.print("\nEnter a number corresponding to one of the"
+ " following choices.\n 1. Display Balance"
+ "\n 2. Deposit\n 3. Withdraw\n 4. Log Out\n");
menuChoice = keyboard.nextInt();
if (menuChoice < 1 || menuChoice > 4){
System.out.println("error");
}
}while (menuChoice < 1 || menuChoice > 4);
return menuChoice;
}
public static void displayBalance(double x)
{
System.out.printf("\nYour current balance is $%.2f\n", x);
}
public static double deposit(double x, double y)
{
return x + y;
}
public static double withdraw(double x, double y)
{
if (y > x){
return x;
}
return x-y;
}
public static void main(String[] args) {
String accNum, pass, origBal = "error";
int count = 0, menuOption = 0;
double depositAmt, withdrawAmt, currentBal;
//loop that will count the number of login attempts
//you make and will exit program if it is more than 3.
//as long as oriBal equals an error.
do{
System.out.println("Please enter your account number: ");
accNum = keyboard.next();
System.out.println("Enter your password: ");
pass = keyboard.next();
origBal = checkID(accNum, pass);
count++;
if (count >= 3 && origBal.equals("error")){
System.out.print("Maximum login attempts reached.");
System.exit(0);
}
if (!(origBal.equals("error"))){
System.out.println("\nYour balance is $ "+ origBal);
}
else
System.out.println(origBal);
}while(origBal.equals("error"));
currentBal=Double.parseDouble(origBal);
//this loop will keep track of the options that
//the user inputs in for the menu. and will
//give the option of deposit, withdraw, or logout.
while (menuOption != 4)
{
menuOption=menu();
switch (menuOption)
{
case 1:
displayBalance(currentBal);
break;
case 2:
System.out.print("Enter the amount you wish to deposit: $ ");
depositAmt = keyboard.nextDouble();
currentBal = deposit(depositAmt, currentBal);
System.out.printf("Your new balance is $%.2f\n", currentBal);
break;
case 3:
System.out.print("Enter the amount you wish to withdraw: $ ");
withdrawAmt = keyboard.nextDouble();
if (withdrawAmt > currentBal)
System.out.println("error");
currentBal = withdraw(currentBal, withdrawAmt);
System.out.printf("Your new balance is $%.2f\n",currentBal);
break;
case 4:
System.exit(0);
break;
}
}
}
}
这是我的更新版本。
感谢您的建议。
这与双提交问题无关。您应该将标签更改为Java。 – Makoto 2014-11-02 22:48:32