在java中，如果用户输入了错误的输入，你如何让程序重新启动你问他们的问题，例如我在下面发布的代码中我得到了问题选择0-9之间的数字我如何制作如果用户输入错误的输入（如10或更高）或字符串，它会在该问题上重新启动。我非常感谢任何提示或建议。
import java.util.Scanner;
public class Project2 {
public static void main(String[] args) {
String PlayAgain = "Y";
while (PlayAgain.equals("Y")) {
// Generate a secret Numbers
int number1 = (int) (Math.random() * 10);
int number2 = (int) (Math.random() * 10);
int number3 = (int) (Math.random() * 10);
int arr[] = new int[3];
arr[0] = number1;
arr[1] = number2;
arr[2] = number3;
boolean g1;
boolean g2;
boolean g3;
g1 = false;
g2 = false;
g3 = false;
// Show secret numbers
System.out.println(arr[0] + ", " + arr[1] + ", " + arr[2]);
Scanner input = new Scanner(System.in);
// Prompt the user to enter a guess
System.out.print("Enter your lottery pick (0-9): ");
int guess1 = input.nextInt();
if (guess1 > 9) {
System.out
.println("Wrong input enter only 1 number between 0-9: ");
} else {
}
System.out.print("Enter your lottery pick (0-9): ");
int guess2 = input.nextInt();
if (guess2 > 9) {
System.out
.println("Wrong input enter only 1 number between 0-9: ");
} else {
}
System.out.print("Enter your lottery pick (0-9): ");
int guess3 = input.nextInt();
if (guess3 > 9) {
System.out
.println("Wrong input enter only 1 number between 0-9: ");
} else {
continue;
}
// Show secret numbers and your numbers
System.out.println("The Secret Numbers are " + arr[0] + (", ")
+ arr[1] + (", ") + arr[2]);
System.out.println("Your Numbers are " + guess1 + (", ") + guess2
+ (", ") + guess3);
if (guess1 == arr[0] && guess2 == arr[1] && guess3 == arr[2]) {
System.out
.println("Three Matching in Exact order, You Won $100,000 ");
} else if ((
(guess1 == arr[1] || guess1 == arr[2])
&& (guess2 == arr[0] || guess2 == arr[2]) && (guess3 == arr[0] || guess3 == arr[1]))
||
((guess1 == arr[0])
&& (guess2 == arr[1] || guess2 == arr[2]) && (guess3 == arr[1] || guess3 == arr[2]))
||
((guess2 == arr[1])
&& (guess3 == arr[0] || guess3 == arr[1]) && (guess1 == arr[0] || guess1 == arr[2]))
||
((guess3 == arr[2])
&& (guess2 == arr[0] || guess2 == arr[2]) && (guess1 == arr[1] || guess1 == arr[0])))
{
System.out
.println("Three Matching in Different order, You Won $10,000 ");
} else if (
((guess1 == arr[0] || guess1 == arr[1] || guess1 == arr[2]) && (guess2 == arr[0]
|| guess2 == arr[1] || guess2 == arr[2]))
&& (guess3 != arr[0] || guess3 != arr[1] || guess3 != arr[2])
||
((guess1 == arr[0] || guess1 == arr[1] || guess1 == arr[2]) && (guess3 == arr[0]
|| guess3 == arr[1] || guess3 == arr[2]))
&& (guess2 != arr[0] || guess2 != arr[1] || guess2 != arr[2])
||
((guess2 == arr[0] || guess2 == arr[1] || guess2 == arr[2]) && (guess3 == arr[0]
|| guess3 == arr[1] || guess3 == arr[2]))
&& (guess1 != arr[0] || guess1 != arr[1] || guess1 != arr[2])
) {
System.out.println("Any Two Numbers Matching, You Win $1,000 ");
} else if ((guess1 == arr[0] || guess1 == arr[1] || guess1 == arr[2])
&& (guess2 != arr[0] || guess2 != arr[1] || guess2 != arr[2])
&& (guess3 != arr[0] || guess3 != arr[1] || guess3 != arr[2])
||
(guess2 == arr[0] || guess2 == arr[1] || guess2 == arr[2])
&& (guess1 != arr[0] || guess1 != arr[1] || guess1 != arr[2])
&& (guess3 != arr[0] || guess3 != arr[1] || guess3 != arr[2])
||
(guess3 == arr[0] || guess3 == arr[1] || guess3 == arr[2])
&& (guess1 != arr[0] || guess1 != arr[1] || guess1 != arr[2])
&& (guess2 != arr[0] || guess2 != arr[1] || guess2 != arr[2])
)// close if
{
System.out.println("Any One Number Matching, You Win $10 ");
} else {
System.out.println("You Lose Sorry ");
}
System.out.println("Would you like to play again? Y/N ");
PlayAgain = input.next();
PlayAgain = PlayAgain.toUpperCase();
}// end of while loop
} // end of main
} // end of class
抱歉，如果代码很难在初学者处阅读，我确实在发布之前使用了ctrl + shift + f来格式化代码。
答案 0 :(得分：2)
最好将一些逻辑分解为单独的方法来处理代码重用。但是，为了使其与您显示的内容保持一致并使示例易于阅读，您可以在输入数字时执行以下操作：
boolean isValid = false;
while (!isValid) {
System.out.print("Enter your lottery pick (0-9): ");
int guess1 = -1;
try {
guess1 = input.nextInt();
} catch (Exception e) {
// Read any pending input which would be invalid characters at this point
input.next();
}
if (guess1 > 9 || guess1 < 0) {
System.out.println("Wrong input enter only 1 number between 0-9: ");
} else {
isValid = true;
}
}
答案 1 :(得分：0)
你的代码“不优雅”。尝试使用这样的模式：
伪java代码：
while (true) {
// get input
if (input is "exit")
break;
if (input is bad)
continue;
// process input
}