如何在 while 循环中运行扫描程序-解网

问：

    public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    
    System.out.println("1 - login");
    System.out.println("2 - regrister");

    int firstSelection = scanner.nextInt();

    while(firstSelection > 2 || firstSelection <1) {
        System.out.println(firstSelection+" is not a valid entry");
        int firstSelection = scanner.nextInt();
    }
    System.out.println("you picked "+firstSelection);
    }

问题：

重复变量firstSelection

我想做什么：

要求用户输入
当 while 循环运行时。如果 firstSelection 不是有效的输入，我想再次运行扫描程序，直到他们输入有效的响应

我尝试过：

    System.out.println("1 - login");
    System.out.println("2 - regrister");
    
    boolean fs;
    while((fs = scanner.nextInt() != 1) || (fs = scanner.nextInt() != 2)) {
        System.out.println(fs+" is not a valid entry");
    }
    System.out.println("you picked "+fs);

问题：

如果我输入 1。我没有收到印刷线说.如果我再次输入它，它会告诉我.you picked 1true is not a valid entry
如果我输入了不正确的响应，它将持续响应true is not a valid entry

while-loop 复制 java.util.scanner

public static void main(String[] args) {
    int firstSelection;
    Scanner scanner = new Scanner(System.in);

    while (true) {
        System.out.println("1 - login");
        System.out.println("2 - regrister");
        firstSelection = scanner.nextInt();
        if (firstSelection == 1 || firstSelection == 2)
            break;
        else {
            System.out.println(firstSelection + " is not a valid entry");
            System.out.println("---------------------");
        }
    }

    System.out.println("you picked " + firstSelection);

}

1赞 Jay 7/3/2022 #2

您也可以使用 do-while 循环

'do{

您的代码在这里

}while（条件）'

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如何在 while 循环中运行扫描程序

How to run scanner in a while loop

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