如何在我的程序中使用 try/catch/finally 过滤扫描仪输入错误?
How to filter Scanner input errors with try/catch/finally in my programm?
我写了这个猜谜小游戏,你必须猜出一个随机数。我完成了这个程序,但我想做的最后一件事是:当用户应该输入一个数字及其和 InputMissmatching 错误或其他错误时,系统告诉他必须输入一个大于 0 的数字。
但是在这个 do-while 循环之后 Scanner 的变量不再起作用了!我必须如何设置 try/catch/finally 循环以仅获取整数并且在它不是整数或 0 时不会崩溃?
问题是 guessNumber 和 numberOfUser 变量现在还没有初始化!
行:37,53 那么我必须在 try/catch 循环中更改什么?
package gessinggame;
import java.util.InputMismatchException;
import java.util.Random;
import java.util.Scanner;
public class GessingGame {
public static void main(String[] args) {
//<editor-fold desc="Start Variables and Objects">
Random random = new Random();
Scanner input = new Scanner(System.in);
int counter = 0;
int numberOfUser;
int guessNumber;
int x = 1;
System.out.print("Try to guess my number! What should be the highest number I can go up to?: ");
do{
try{
numberOfUser = input.nextInt();
guessNumber = random.nextInt(numberOfUser);
x = 2;
}catch(Exception e)
{
System.out.print("That doesn't work! Please enter an integer higher than 0 :");
x = 1;
}
}while(x == 1);
//</editor-fold>
//<editor-fold desc="do-while loop (higher/lower/equal)">
System.out.println("Try to guess my number! Its from 0 to " + numberOfUser + " !");
System.out.println("---------------------------------------------------");
do{
int userguess = input.nextInt();
if(userguess > numberOfUser)
{
System.out.println("Oh man, at the beginning you said that the highest number is: " + numberOfUser);
}
else{
if(userguess < 0)
{
System.out.println("My number is always taller than 0");
} else{
if(guessNumber < userguess)
{
System.out.println("lower");
counter++;
}
if(guessNumber > userguess)
{
System.out.println("higher");
counter++;
}
if(userguess == guessNumber)
{
counter++;
break;
}
}
}
}while(true);
//</editor-fold>
//<editor-fold desc="print final result">
System.out.println("You guessed my number! My number was: " + guessNumber + "! You needed " + counter + " attempts!");
//</editor-fold>
}
}
所以问题是首先你当然需要捕获异常。在 try catch 中,您必须使用 input.nextLine();
清除缓冲区
所以这应该有效:
public static void main(String[] args)
{
// <editor-fold desc="Start Variables and Objects">
Random random = new Random();
Scanner input = new Scanner(System.in);
int counter = 0;
int numberOfUser = 0;
int guessNumber = 0;
int x = 1;
System.out.print("Try to guess my number! What should be the highest number I can go up to?: ");
do
{
try
{
numberOfUser = input.nextInt();
guessNumber = random.nextInt(numberOfUser);
x = 2;
}
catch (Exception e)
{
System.out.print("That doesn't work! Please enter an integer higher than 0 :");
x = 1;
}
} while (x == 1);
// </editor-fold>
// <editor-fold desc="do-while loop (higher/lower/equal)">
System.out.println("Try to guess my number! Its from 0 to " + numberOfUser + " !");
System.out.println("---------------------------------------------------");
do
{
int userguess = 0;
try
{
userguess = input.nextInt();
}
catch (InputMismatchException e)
{
System.out.println("Please enter a valid number!");
input.nextLine();
}
if (userguess > numberOfUser)
{
System.out.println("Oh man, at the beginning you said that the highest number is: " + numberOfUser);
}
else
{
if (userguess < 0)
{
System.out.println("My number is always taller than 0");
}
else
{
if (guessNumber < userguess)
{
System.out.println("lower");
counter++;
}
if (guessNumber > userguess)
{
System.out.println("higher");
counter++;
}
if (userguess == guessNumber)
{
counter++;
break;
}
}
}
} while (true);
// </editor-fold>
// <editor-fold desc="print final result">
System.out.println(
"You guessed my number! My number was: " + guessNumber + "! You needed " + counter + " attempts!");
// </editor-fold>
}
在您的 try/catch
块中添加 input.nextLine()。
在每个 Scanner.nextInt
之后调用 Scanner.nextLine
调用以消耗该行的其余部分,包括换行符。
package gessinggame;
import java.util.InputMismatchException;
import java.util.Random;
import java.util.Scanner;
public class GessingGame {
public static void main(String[] args) {
//<editor-fold desc="Start Variables and Objects">
Random random = new Random();
Scanner input = new Scanner(System.in);
int counter = 0;
int numberOfUser = 0;
int guessNumber = 0;
int x = 1;
System.out.print("Try to guess my number! What should be the highest number I can go up to?: ");
do{
try{
numberOfUser = input.nextInt();
guessNumber = random.nextInt(numberOfUser);
x = 2;
}catch(Exception e)
{
System.out.print("That doesn't work! Please enter an integer higher than 0 :");
input.nextLine();
x = 1;
}
}while(x == 1);
System.out.println("Try to guess my number! Its from 0 to " + numberOfUser + " !");
System.out.println("---------------------------------------------------");
do{
int userguess = input.nextInt();
if(userguess > numberOfUser)
{
System.out.println("Oh man, at the beginning you said that the highest number is: " + numberOfUser);
}
else{
if(userguess < 0)
{
System.out.println("My number is always taller than 0");
} else{
if(guessNumber < userguess)
{
System.out.println("lower");
counter++;
}
if(guessNumber > userguess)
{
System.out.println("higher");
counter++;
}
if(userguess == guessNumber)
{
counter++;
break;
}
}
}
}while(true);
System.out.println("You guessed my number! My number was: " + guessNumber + "! You needed " + counter + " attempts!");
}
}
我写了这个猜谜小游戏,你必须猜出一个随机数。我完成了这个程序,但我想做的最后一件事是:当用户应该输入一个数字及其和 InputMissmatching 错误或其他错误时,系统告诉他必须输入一个大于 0 的数字。 但是在这个 do-while 循环之后 Scanner 的变量不再起作用了!我必须如何设置 try/catch/finally 循环以仅获取整数并且在它不是整数或 0 时不会崩溃?
问题是 guessNumber 和 numberOfUser 变量现在还没有初始化! 行:37,53 那么我必须在 try/catch 循环中更改什么?
package gessinggame;
import java.util.InputMismatchException;
import java.util.Random;
import java.util.Scanner;
public class GessingGame {
public static void main(String[] args) {
//<editor-fold desc="Start Variables and Objects">
Random random = new Random();
Scanner input = new Scanner(System.in);
int counter = 0;
int numberOfUser;
int guessNumber;
int x = 1;
System.out.print("Try to guess my number! What should be the highest number I can go up to?: ");
do{
try{
numberOfUser = input.nextInt();
guessNumber = random.nextInt(numberOfUser);
x = 2;
}catch(Exception e)
{
System.out.print("That doesn't work! Please enter an integer higher than 0 :");
x = 1;
}
}while(x == 1);
//</editor-fold>
//<editor-fold desc="do-while loop (higher/lower/equal)">
System.out.println("Try to guess my number! Its from 0 to " + numberOfUser + " !");
System.out.println("---------------------------------------------------");
do{
int userguess = input.nextInt();
if(userguess > numberOfUser)
{
System.out.println("Oh man, at the beginning you said that the highest number is: " + numberOfUser);
}
else{
if(userguess < 0)
{
System.out.println("My number is always taller than 0");
} else{
if(guessNumber < userguess)
{
System.out.println("lower");
counter++;
}
if(guessNumber > userguess)
{
System.out.println("higher");
counter++;
}
if(userguess == guessNumber)
{
counter++;
break;
}
}
}
}while(true);
//</editor-fold>
//<editor-fold desc="print final result">
System.out.println("You guessed my number! My number was: " + guessNumber + "! You needed " + counter + " attempts!");
//</editor-fold>
}
}
所以问题是首先你当然需要捕获异常。在 try catch 中,您必须使用 input.nextLine();
清除缓冲区所以这应该有效:
public static void main(String[] args)
{
// <editor-fold desc="Start Variables and Objects">
Random random = new Random();
Scanner input = new Scanner(System.in);
int counter = 0;
int numberOfUser = 0;
int guessNumber = 0;
int x = 1;
System.out.print("Try to guess my number! What should be the highest number I can go up to?: ");
do
{
try
{
numberOfUser = input.nextInt();
guessNumber = random.nextInt(numberOfUser);
x = 2;
}
catch (Exception e)
{
System.out.print("That doesn't work! Please enter an integer higher than 0 :");
x = 1;
}
} while (x == 1);
// </editor-fold>
// <editor-fold desc="do-while loop (higher/lower/equal)">
System.out.println("Try to guess my number! Its from 0 to " + numberOfUser + " !");
System.out.println("---------------------------------------------------");
do
{
int userguess = 0;
try
{
userguess = input.nextInt();
}
catch (InputMismatchException e)
{
System.out.println("Please enter a valid number!");
input.nextLine();
}
if (userguess > numberOfUser)
{
System.out.println("Oh man, at the beginning you said that the highest number is: " + numberOfUser);
}
else
{
if (userguess < 0)
{
System.out.println("My number is always taller than 0");
}
else
{
if (guessNumber < userguess)
{
System.out.println("lower");
counter++;
}
if (guessNumber > userguess)
{
System.out.println("higher");
counter++;
}
if (userguess == guessNumber)
{
counter++;
break;
}
}
}
} while (true);
// </editor-fold>
// <editor-fold desc="print final result">
System.out.println(
"You guessed my number! My number was: " + guessNumber + "! You needed " + counter + " attempts!");
// </editor-fold>
}
在您的 try/catch
块中添加 input.nextLine()。
在每个 Scanner.nextInt
之后调用 Scanner.nextLine
调用以消耗该行的其余部分,包括换行符。
package gessinggame;
import java.util.InputMismatchException;
import java.util.Random;
import java.util.Scanner;
public class GessingGame {
public static void main(String[] args) {
//<editor-fold desc="Start Variables and Objects">
Random random = new Random();
Scanner input = new Scanner(System.in);
int counter = 0;
int numberOfUser = 0;
int guessNumber = 0;
int x = 1;
System.out.print("Try to guess my number! What should be the highest number I can go up to?: ");
do{
try{
numberOfUser = input.nextInt();
guessNumber = random.nextInt(numberOfUser);
x = 2;
}catch(Exception e)
{
System.out.print("That doesn't work! Please enter an integer higher than 0 :");
input.nextLine();
x = 1;
}
}while(x == 1);
System.out.println("Try to guess my number! Its from 0 to " + numberOfUser + " !");
System.out.println("---------------------------------------------------");
do{
int userguess = input.nextInt();
if(userguess > numberOfUser)
{
System.out.println("Oh man, at the beginning you said that the highest number is: " + numberOfUser);
}
else{
if(userguess < 0)
{
System.out.println("My number is always taller than 0");
} else{
if(guessNumber < userguess)
{
System.out.println("lower");
counter++;
}
if(guessNumber > userguess)
{
System.out.println("higher");
counter++;
}
if(userguess == guessNumber)
{
counter++;
break;
}
}
}
}while(true);
System.out.println("You guessed my number! My number was: " + guessNumber + "! You needed " + counter + " attempts!");
}
}