Java while循环没有终止！ [英] Java while loop not terminating!

问题描述

我有一个Java代码，其中while循环没有终止..如果我使用文件而不是Std，我得到正确的结果..请指出我的错误..代码：

 public static void main（String args []）抛出异常{
 int y; 
 int n; 
 Scanner sc = new Scanner（System.in）; 
 int k = sc.nextInt（）; 
 y = 0; 
 n = 0; 
 while（sc.hasNextLine（））{
 String c = sc.next（）; 
模式p = Pattern.compile（[0-9] {1,2}）; 
 Matcher m = p.matcher（c）; 
 if（m.matches（））{
 if（c.equals（19）|| c.equals（20））{
 y + = 4; 
} 
 else {
 n + = 3; 
} 
} 
} 
 System.out.println（Y是：+ y +N是：+ n）; 
 System.out.println（y> n？Date：No Date）; 
 
} 
 

提前致谢！



我的尝试：



在循环中输入扫描仪输入！

解决方案

嗯...没有这样的输入来自控制台时不是下一行的东西。



您可能想要检查返回的空字符串以表示退出，而不是检查hasNextLine或类似的东西。

Quote：

如果我使用的是文件而不是Std，我会得到正确的结果..

你的错误是键盘永远不会结束，你在键盘前等待的事实并不是输入的结束。

返回时间，当我在C中这样做时，文件的键盘末端是Ctrl-Z。

如果它不起作用，你将不得不考虑一个特殊的输入，它将作为一个结束文件。

I have a code in Java for which while loop is not terminating.. If I use a file instead of Std, I get correct result.. Please point out my mistake.. Code:

public static void main(String args[] ) throws Exception {
    int y;
    int n;
    Scanner sc = new Scanner(System.in);
        int k = sc.nextInt();
        y = 0;
        n = 0;
        while(sc.hasNextLine()){
            String c = sc.next();
            Pattern p = Pattern.compile("[0-9]{1,2}");
            Matcher m = p.matcher(c);
            if(m.matches()){
                if(c.equals("19") || c.equals("20")){
                    y += 4;
                }
                else{
                    n += 3;
                }
            }
        }
System.out.println("Y Is: " + y + "N is : " + n);
System.out.println(y > n ? "Date" : "No Date");

}

Thanks in Advance!

What I have tried:

Taking Scanner input inside while loop!

解决方案

Ummm... There is no such thing as NOT a next line when input is coming from the console.

Instead of checking for hasNextLine, you might want to check for an empty string returned to signal a quit or something like that.

Quote:

If I use a file instead of Std, I get correct result..

Your mistake is that the keyboard never ends, the fact that you wait in front of keyboard is not an end of input.
Back in time, when I did this in C, the keyboard end of file was Ctrl-Z.
If it don't work, you will have to think about a special input that will act as an end of file.

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