使用java.util.Scanner逐字节读取文件 [英] using java.util.Scanner to read a file byte by byte

问题描述

我正在尝试使用java.util.Scanner逐个字符地读取一行文件。但是我得到了这个异常：

 线程main中的异常java.util.InputMismatchException：对于输入字符串：我的文件的内容
 at java.util.Scanner.nextByte（Scanner.java:1861）
 at java.util.Scanner.nextByte（Scanner.java:1814）
 at p008。 main（p008.java:18）<  - 我在哪里行scan.nextByte（）
  

这是我的代码：

  public static void main（String [] args）throws FileNotFoundException {
 File source = new File （file.txt）; 
扫描仪扫描仪=新扫描仪（来源）; 
 while（scanner.hasNext（））{
 System.out.println（（char）scanner.nextByte （））; 
} 
 scanner.close（）
} 
  

<有没有人对我可能做错了什么有任何想法？

编辑：我意识到我写了hasNext（）而不是hasNextByte（）。但是如果我这样做的话它不打印任何东西。

解决方案

为什么你想要使用扫描器逐字节读取文件？这就像用手推车搬运口袋一样。 （如果你真的需要一个独轮车换口袋，请告诉我，这样我才能成为你的朋友。）

但严重的是：Class InputStream 简单可靠地从文件中读取字节，并且不执行任何其他操作。

Class scanner 最近被引入Java API，因此教科书示例可以从文件中提取数据，而不是通常使用级联的新的BufferedReader（新的InputStream）。它的专长是从自由格式的输入文件中输入数字和字符串。 nextByte（）方法实际上从输入流中读取一个或几个十进制数字（如果它们在那里）并将扫描的数字转换为单个字节值。 / p>

如果您正在读取字节，为什么要将它们输出为 char s？字节不字符，并且在某些地方强力互换将失败。如果你想看到那些字节的值，按原样打印它们，你会看到0到25​​5之间的小整数。

如果你想阅读<来自文件的code> char ， FileReader 是适合您的课程。

I'm trying to read a one line file character by character using java.util.Scanner. However I'm getting this exception":

Exception in thread "main" java.util.InputMismatchException: For input string: "contents of my file"
    at java.util.Scanner.nextByte(Scanner.java:1861)
    at java.util.Scanner.nextByte(Scanner.java:1814)
    at p008.main(p008.java:18) <-- line where I do scanner.nextByte()

Here's my code:

public static void main(String[] args) throws FileNotFoundException {
    File source = new File("file.txt");
    Scanner scanner = new Scanner(source);
    while(scanner.hasNext()) {
        System.out.println((char)scanner.nextByte());
    }
    scanner.close()
}

Does anyone have any ideas as to what I might be doing wrong?

Edit: I realized I wrote hasNext() instead of hasNextByte(). However if I do that it doesn't print out anything.

解决方案

Why on earth would you want to use a scanner to read a file byte by byte? That's like using a wheelbarrow to transport your pocket change. (If you really need a wheelbarrow for your pocket change, let me know so I can become your friend).

But seriously: Class InputStream reads bytes from a file, simply and reliably, and does nothing else.

Class scanner was recently introduced into the Java API so textbook examples could pull data out of a file with less pain than is usually involved with using the cascade of new BufferedReader(new InputStream). Its specialty is inputting numbers and strings from free-form input files. The nextByte() method actually reads one or a few decimal digits from the input stream (if they're there) and converts the number thus scanned into a single byte value.

And if you're reading bytes, why do you want to output them as chars? Bytes are not chars, and brute-force interconverting will fail in some places. If you want to see the values of those bytes, print them out as they are and you'll see small integers between 0 and 255.

If you want to read chars from a file, FileReader is the class for you.

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