异常处理，捕获原因while循环停止 [英] Exception handling, catch causes while loop to stop
问题描述
该文件包含：12 5 sd 67 4 cy
我想要显示：
12
5
输入错误
67
4
输入错误
但是，它只给我12,5，然后输入错误，它停止。
我已经尝试将所有内容都放在一个循环中，并且随着输入异常循环而循环。
public static void readNumbers（）
{
文件inputFile =新文件（C：/users/AC/Desktop/input.txt）;
尝试
{
扫描仪阅读器=新的扫描仪（inputFile）;
while（reader.hasNext（））
{
int num = reader.nextInt（）;
System.out.println（Number read：+ num）;
}
}
catch（InputMismatchException e）
{
System.out.println（Input error）;
}
catch（FileNotFoundException e2）
{
System.out.println（File not found！）;
}
}
}
我错过了循环继续阅读下一个int等等？
try / catch块需要在循环。
当抛出异常时，控件会尽可能地发生，直到遇到一个catch块（在你的情况下，它不在你的循环之外） / p>
public static void readNumbers（）
{
文件inputFile =新文件：/users/AC/Desktop/input.txt）;
尝试{
扫描仪阅读器=新的扫描仪（inputFile）;
while（reader.hasNext（））
{
try
{
int num = reader.nextInt（）;
System.out.println（Number read：+ num）;
}
catch（InputMismatchException e）
{
System.out.println（Input error）;
}
}
}
catch（FileNotFoundException e2）
{
System.out.println（File not found！）;
}
}
我已经尝试把所有的东西放在一个循环中，并且循环不断地
与输入例外。
你提到你已经试过了我需要更多关于你遇到的问题的细节，因为这是正确的方法。离开我的头顶，只是一个希望，也许reader.nextInt（）不会提高读者在异常发生时在文件中的位置，因此一次又一次地调用nextInt读取相同的非整数块。
也许你的catch块需要调用reader.getSomethingElse？像reader.next（）？
这是一个想法，我还没有测试：
public static void readNumbers（）
{
文件inputFile =新文件（C：/users/AC/Desktop/input.txt）;
尝试{
扫描仪阅读器=新的扫描仪（inputFile）;
while（reader.hasNext（））
{
try
{
int num = reader.nextInt（）;
System.out.println（Number read：+ num）;
}
catch（InputMismatchException e）
{
System.out.println（Input error）;
reader.next（）; //这条线是新
}
}
}
catch（FileNotFoundException e2）
{
System.out.println（File not found！ ）;
}
}
我对推进读者是正确的。
根据扫描器的Java文档：
将输入的下一个标记作为int进行扫描。如果下一个令牌不能被翻译成
有效的int值，则此方法将抛出
InputMismatchException，如下所述。 如果翻译成功，
，扫描器将超过匹配的输入。
< a href =http://docs.oracle.com/javase/7/docs/api/ =nofollow> http://docs.oracle.com/javase/7/docs/api/
I have a file that I need to read, print out the integers, catch exception and continue with the next integer to display, and so on until there are no more integers.
The file contains: 12 5 sd 67 4 cy
I want it to display:
12
5
Input error
67
4
Input error
However, it only gives me 12, 5, followed by input error, and it stops. I've tried putting everything into a while loop and it loops endlessly with the input exception.
public static void readNumbers()
{
File inputFile = new File ("C:/users/AC/Desktop/input.txt");
try
{
Scanner reader = new Scanner(inputFile);
while(reader.hasNext())
{
int num = reader.nextInt();
System.out.println("Number read: " +num);
}
}
catch (InputMismatchException e)
{
System.out.println("Input error ");
}
catch (FileNotFoundException e2)
{
System.out.println("File not found!");
}
}
}
What am I missing so that the loop continues reading the next int and so on?
The try/catch block needs to be inside the loop.
When an exception is thrown, control breaks out as far as it can until it encounters a catch block, which in your case, is outside of your loop.
public static void readNumbers()
{
File inputFile = new File ("C:/users/AC/Desktop/input.txt");
try {
Scanner reader = new Scanner(inputFile);
while(reader.hasNext())
{
try
{
int num = reader.nextInt();
System.out.println("Number read: " +num);
}
catch (InputMismatchException e)
{
System.out.println("Input error ");
}
}
}
catch (FileNotFoundException e2)
{
System.out.println("File not found!");
}
}
I've tried putting everything into a while loop and it loops endlessly with the input exception.
You mentioned that you tried this already. I need more details on the problem you encountered because this is the right way to do it. Off the top of my head, just a hunch, is that perhaps reader.nextInt() does not advance the reader's position in the file when the exception occurs and therefore calling nextInt again and again reads the same non-integer chunk.
Perhaps your catch block needs to call reader.getSomethingElse? Like reader.next()?
This is an idea and I have not tested it:
public static void readNumbers()
{
File inputFile = new File ("C:/users/AC/Desktop/input.txt");
try {
Scanner reader = new Scanner(inputFile);
while(reader.hasNext())
{
try
{
int num = reader.nextInt();
System.out.println("Number read: " +num);
}
catch (InputMismatchException e)
{
System.out.println("Input error ");
reader.next(); // THIS LINE IS NEW
}
}
}
catch (FileNotFoundException e2)
{
System.out.println("File not found!");
}
}
[Edit 9:32PM]
I am correct about advancing the reader.
Per the Java doc for Scanner:
Scans the next token of the input as an int. This method will throw InputMismatchException if the next token cannot be translated into a valid int value as described below. If the translation is successful, the scanner advances past the input that matched.
http://docs.oracle.com/javase/7/docs/api/
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