我必须制作一个
的计算器使用正数输入运行程序,显示输出并询问用户是否要循环。
使用字符串输入(两个而不是2个)运行程序,使用try和catch显示一条消息,告诉用户错误,并询问用户是否要循环。
使用负数输入运行程序,显示错误消息而不显示输出,并询问用户是否要循环。
当我尝试抓住时,我会在variable not have been initialized
之后获取变量try catch
。
try {
System.out.print("Enter loan amount: ");
loanNum = Double.parseDouble(in.nextLine());
System.out.print("Enter rate: ");
rateNum = Double.parseDouble(in.nextLine());
System.out.print("Enter number years: ");
yearNum = Double.parseDouble(in.nextLine());
}
catch(NumberFormatException e) {
System.out.println ("You must enter positive numeric data!");
}
如果没有try catch
我无法在不使用System.exit(0);
显示输出的情况下弄清楚如何进行数字2。这结束了用户能够输入循环。
我不确定如何修复我的while循环。当我运行程序时,它只运行一次然后循环一次。之后它会在没有提示的情况下自动循环并在一行上吐出线条,如:
Would you like to calculate again (y/n):
Enter loan amount:
代码:
package whileloopyn;
import java.util.Scanner;
public class Whileloopyn {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
//Declare Variables
double loanNum;
double rateNum;
double trateNum;
double yearNum;
double monthNum;
double equNum;
double outputNum;
//Prompt for input and try catch for exception error (rate inputed as two)
System.out.print("Enter loan amount: ");
loanNum = Double.parseDouble(in.nextLine());
System.out.print("Enter rate: ");
rateNum = Double.parseDouble(in.nextLine());
System.out.print("Enter number years: ");
yearNum = Double.parseDouble(in.nextLine());
//Postive input data check (negative then ask again)
if(loanNum <= 0 || rateNum <=0 || yearNum <=0)
{
System.out.println("You must enter positive numeric data! ");
System.exit(0);
}
//Convert years to months
monthNum = yearNum * 12;
//Convert rate to percent and monthly
trateNum= (rateNum / 100) /12;
//Complete numerator
equNum = Math.pow((1+ trateNum), monthNum );
//Plug equNum into formula
outputNum = trateNum * loanNum * (equNum / (equNum - 1));
//output answer
System.out.printf("The monthly payment is: $ %.2f%n", outputNum);
//prompt user y n to run program again
System.out.println("Would you like to calculate again (y/n): ");
String loop = in.nextLine();
//while loop with (input
boolean isContinuing = true;
while (isContinuing) {
while(loop.equals("y")){
System.out.print("Enter loan amount: ");
loanNum = in.nextDouble();
System.out.print("Enter rate: ");
rateNum = in.nextDouble();
System.out.print("Enter number years: ");
yearNum = in.nextDouble();
//Postive input data check (negative then loop again)
if(loanNum <= 0 || rateNum <=0 || yearNum <=0)
{
System.out.println("You must enter positive numeric data! ");
System.exit(0);
}
//Convert years to months
monthNum = yearNum * 12;
//Convert rate to percent and monthly
trateNum= (rateNum / 100) /12;
//Complete numerator
equNum = Math.pow((1+ trateNum), monthNum );
//Plug equNum into formula
outputNum = trateNum * loanNum * (equNum / (equNum - 1));
//output answer
System.out.printf("The monthly payment is: $ %.2f%n", outputNum);
//ask user if you want to use program again
System.out.printf("Would you like to calculate again (y/n): ");
if(loop.equals("n"))
{
System.exit(0);
}
}
}
}
}
有人建议(input.equals(String)
)是我应该如何比较while循环的字符串并使用in.nextLine();
。
答案 0 :(得分:1)
如果用户按Y
,您必须继续该循环:
System.out.printf("Would you like to calculate again (y/n): ");
Scanner s = new Scanner(System.in);
if(s.nextLine().equalsIgnoreCase("y")) {
continue;
} else {
break;
}
而不是while(loop.equals("y")){
你应该写while(true) {
,因为你已经在那个循环中检查过了