java - 我的程序终止了，没有扫描字符串

This question already has answers here:

Scanner is skipping nextLine() after using next() or nextFoo()?

（19个回答）


6年前关闭。





当我执行代码时，我的程序将终止而不扫描字符串。

double x, y;
    String s;
    Scanner scan = new Scanner(System.in);
    System.out.println("Enter Number: ");
    x = scan.nextDouble();
    System.out.println("Enter Number 2: ");
    y = scan.nextDouble();
    System.out.println("Enter Operater: x,+,/,-");
    s = scan.nextLine();
    if(s.equals("x"))
    {
        System.out.print(x * y);

    }
    else if(s.equals("+"))
    {
        System.out.print(x + y);

    }
    else if(s.equals("/"))
    {
        System.out.print(x / y);

    }
    else if(s.equals("-"))
    {
        System.out.print(x - y);

    }
    scan.close();

我的程序在s = scan.nextline();之前结束
它怎么结束了？

最佳答案

行尾您留在缓冲区中。
next( )从缓冲区读取令牌，直到下一个空格，而nextLine( )最多读取\n

...
System.out.print("Enter Number 2: ");
y = scan.nextDouble();
System.out.print("Enter Operater: x,+,/,-");
s = scan.next();
...

Enter Number: 1
Enter Number 2: 2
Enter Operater: x,+,/,--
-1.0