Java while循环,switch语句
当我输入“p”时,我遇到了一个问题,在它完成后,它再次重复while循环的顶部,在那里,用户必须为“input”变量输入一些内容。问题是,用户从未被提示输入任何内容,然后它再次循环,重新打印之前刚刚打印的所有信息。第二次是允许用户输入一些东西。这只有在我运行“p”案例之后才会发生 有人请帮帮我!非常感谢Java while循环,switch语句,java,while-loop,switch-statement,Java,While Loop,Switch Statement,当我输入“p”时,我遇到了一个问题,在它完成后,它再次重复while循环的顶部,在那里,用户必须为“input”变量输入一些内容。问题是,用户从未被提示输入任何内容,然后它再次循环,重新打印之前刚刚打印的所有信息。第二次是允许用户输入一些东西。这只有在我运行“p”案例之后才会发生 有人请帮帮我!非常感谢 package PayandGoParking; /** * Purpose: Input: * * Processing done: * * Output: * * @auth
package PayandGoParking;
/**
* Purpose: Input:
*
* Processing done:
*
* Output:
*
* @author (your name)
* @version (a version number or a date)
*/
import java.util.Scanner;
import java.util.*;
import java.io.*;
import java.text.DecimalFormat;
public class Assignment2 {
public static void main(String[] args) throws IOException {
Calendar now = Calendar.getInstance();
Scanner k = new Scanner(System.in);
DecimalFormat dm = new DecimalFormat("00");
String input = " ",
cardNumber,
x = "x";
double anyKey;
double currentTime,
currentCharge = 0,
securityCode,
totalCharge = 0;
Calendar paidTill;
int min = 0;
while (input != x) {
System.out.println("Welcome to Pay and Go parking");
System.out.println("+ to add 30 minutes ($1.00 charge)");
System.out.println("p to print the ticket");
System.out.println("r to restart");
System.out.println("x to exit the program");
System.out.print("Please enter your selection: ");
input = k.nextLine();
switch (input) {
case "+":
min += 30;
currentCharge += 1;
paidTill = (Calendar) now.clone();
paidTill.add(Calendar.MINUTE, min);
System.out.println("================================================");
System.out.printf("%s%s%s%s%s%.2s%s%.2s\n",
"Current Time: ", now.get(Calendar.MONTH),
"-", now.get(Calendar.DAY_OF_MONTH), " ", now.get(Calendar.HOUR_OF_DAY), ":",
dm.format(now.get(Calendar.MINUTE)));
System.out.printf("%s%s%s%s%s%.2s%s%.2s\n",
"Paid Till: ", paidTill.get(Calendar.MONTH),
"-", paidTill.get(Calendar.DAY_OF_MONTH),
" ", paidTill.get(Calendar.HOUR_OF_DAY), ":",
dm.format(paidTill.get(Calendar.MINUTE)));
System.out.printf("%s%.2f\n", "Current Charge $", currentCharge);
System.out.println("================================================");
break;
case "p":
System.out.print("Enter Credit Card Number: ");
cardNumber = k.nextLine();
System.out.print("Enter 3 digit security code from back of Credit Card: ");
securityCode = k.nextDouble();
System.out.println("=================================================");
System.out.println("Pay and Go Parking");
System.out.println("Lot Location: 123 Main St,");
System.out.println("Honolulu, Hawaii");
System.out.println("-----------------------------");
totalCharge += currentCharge;
paidTill = (Calendar) now.clone();
paidTill.add(Calendar.MINUTE, min);
System.out.printf("%s%s%s%s%s%.2s%s%.2s\n", "Current Time: ",
now.get(Calendar.MONTH), "-",
now.get(Calendar.DAY_OF_MONTH), " ", now.get(Calendar.HOUR_OF_DAY),
":", dm.format(now.get(Calendar.MINUTE)));
System.out.printf("%s%s%s%s%s%.2s%s%.2s\n",
"Paid Till: ", paidTill.get(Calendar.MONTH),
"-", paidTill.get(Calendar.DAY_OF_MONTH),
" ", paidTill.get(Calendar.HOUR_OF_DAY), ":",
dm.format(paidTill.get(Calendar.MINUTE)));
System.out.printf("%s%.2f\n", "Total charged to Credit Card $", currentCharge);
System.out.println("==========================================");
System.out.println("Tear off receipt and place on dash");
System.out.print("Press any key to continue");
anyKey = k.nextDouble();
System.out.println("================================================");
paidTill = (Calendar) now.clone();
System.out.printf("%s%s%s%s%s%.2s%s%.2s\n", "Current Time: ",
now.get(Calendar.MONTH),
"-", now.get(Calendar.DAY_OF_MONTH), " ",
now.get(Calendar.HOUR_OF_DAY), ":", dm.format(now.get(Calendar.MINUTE)));
System.out.printf("%s%s%s%s%s%.2s%s%.2s\n",
"Paid Till: ", paidTill.get(Calendar.MONTH),
"-", paidTill.get(Calendar.DAY_OF_MONTH),
" ", paidTill.get(Calendar.HOUR_OF_DAY), ":",
dm.format(paidTill.get(Calendar.MINUTE)));
currentCharge = 0;
min = 0;
System.out.printf("%s%.2f\n", "Current Charge $", currentCharge);
System.out.println("================================================");
break;
case "r":
currentCharge = 0;
min = 0;
paidTill = (Calendar) now.clone();
System.out.println("================================================");
System.out.printf("%s%s%s%s%s%.2s%s%.2s\n",
"Current Time: ", now.get(Calendar.MONTH),
"-", now.get(Calendar.DAY_OF_MONTH), " ",
now.get(Calendar.HOUR_OF_DAY), ":",
dm.format(now.get(Calendar.MINUTE)));
System.out.printf("%s%s%s%s%s%.2s%s%.2s\n",
"Paid Till: ", paidTill.get(Calendar.MONTH),
"-", paidTill.get(Calendar.DAY_OF_MONTH),
" ", paidTill.get(Calendar.HOUR_OF_DAY),
":", dm.format(paidTill.get(Calendar.MINUTE)));
System.out.printf("%s%.2f\n", "Current Charge $", currentCharge);
System.out.println("================================================");
break;
case "x":
input = x;
break;
}
}
System.out.println("\nTotals for Pay and Go Parking");
System.out.println("========================");
System.out.printf("%s%12s%7.2f\n", "Totals", "$", totalCharge);
}
}
您应该首先解决的问题之一是第44行:
while (input != x)
应该是:
while (!input.equals(x))
使用==或!=比较两个字符串时,不会检查它们是否相等
字符/单词,但如果它们等于相同的字符串含义,则指向内存中的相同位置
我无法运行程序来测试它,因为我没有你的软件包“PayandGoParking”。
您的代码太长,无法通读,无法查找更多问题。
解决此问题后,请尝试使出现问题的代码更简洁。这可能是因为您正在使用System.out.print而不刷新。刷新意味着强制将System.out内部使用的输出缓冲区发送到监视器。只有println保证将您打印的内容发送到监视器。除非字符串中有换行符,否则Regular System.print不会。试一试
System.out.print("Please enter your selection: ");
System.out.flush();
实际上,在每次尝试收集用户输入之前,请尝试添加System.out.flush()。
或者在正在打印的字符串中添加新行
System.out.print("Please enter your selection: \n");
请首先帮助我们将代码示例缩减到可管理的大小,以说明问题。请向我们展示示例-此外,您可能会在编写新代码段时发现问题。