Java Scanner 不等待用户输入
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Java Scanner doesn't wait for user input
提问by user2976389
I am using Java's Scanner to read user input. If I use nextLine only once, it works OK. With two nextLine first one doesnt wait for user to enter the string(second does).
我正在使用 Java 的 Scanner 来读取用户输入。如果我只使用 nextLine 一次，它工作正常。有两个 nextLine 第一个不等待用户输入字符串（第二个）。
Output:
输出：
X: Y: (wait for input)
X：Y：（等待输入）
My code
我的代码
System.out.print("X: ");
x = scanner.nextLine();
System.out.print("Y: ");
y = scanner.nextLine();
Any ideas why could this happen? Thanks
任何想法为什么会发生这种情况？谢谢
采纳答案by Alexis C.
It's possible that you are calling a method like nextInt()before. Thus a program like this:
您可能像nextInt()以前一样调用方法。因此，这样的程序：
Scanner scanner = new Scanner(System.in);
int pos = scanner.nextInt();
System.out.print("X: ");
String x = scanner.nextLine();
System.out.print("Y: ");
String y = scanner.nextLine();
demonstatres the behavior you're seeing.
演示您所看到的行为。
The problem is that nextInt()does not consume the '\n', so the next call to nextLine()consumes it and then it's waiting to read the input for y.
问题是nextInt()不消耗'\n'，所以下一次调用nextLine()消耗它，然后等待读取 的输入y。
You need to consume the '\n'before calling nextLine().
您需要'\n'在调用之前消耗nextLine().
System.out.print("X: ");
scanner.nextLine(); //throw away the \n not consumed by nextInt()
x = scanner.nextLine();
System.out.print("Y: ");
y = scanner.nextLine();
(actually a better way would be to call directly nextLine()after nextInt()).
（实际上更好的方法是在nextLine()之后直接调用nextInt()）。
