简体繁体 English

我可以使用扫描仪从文件中读取字节数组吗？

[英]Can I read a byte array from file using scanner?

原文 2021-11-24 04:12:51 4 2 java/ java.util.scanner

Java.util.scanner can read a variety of data types in including Byte, but what about byte[]? Java.util.scanner可以读取包括Byte在内的多种数据类型，但是byte[]呢？ I've searched for information on Oracle's website as well as other websites, but I'm having trouble finding information on scanning byte[], so I'm wondering if it's even possible.我已经在 Oracle 的网站以及其他网站上搜索了信息，但是我无法找到有关扫描 byte[] 的信息，所以我想知道它是否可能。 I am taking a Java course and we were tasked with storing an encrypted password into a byte[], write the byte[] to file, then read the byte[] back in. Given the requirements of this task, I cannot convert the byte[] to a string, it has to remain a byte[].我正在参加 Java 课程，我们的任务是将加密密码存储到 byte[] 中，将 byte[] 写入文件，然后将 byte[] 读回。鉴于此任务的要求，我无法转换字节[] 到一个字符串，它必须保持一个字节[]。 -- Thank you in advance for your suggestions! -- 提前感谢您的建议！

2 个解决方案

we were tasked with storing an encrypted password into a byte[], write the byte[] to file, then read the byte[] back in.我们的任务是将加密密码存储到 byte[] 中，将 byte[] 写入文件，然后将 byte[] 读回。

A java.util.Scanner is not necessary for this task.此任务不需要java.util.Scanner 。

You can write a byte[] using a OutputStream and read a byte[] using a InputStream .您可以使用OutputStream写入byte[]并使用InputStream读取byte[] 。

There are short-cut methods for reading and writing byte[] arrays as well in the Files utility methods:在Files实用程序方法中也有读写byte[] arrays 的快捷方法：

public static Path write(Path path, byte[] bytes, OpenOption... options) throws IOException
public static byte[] readAllBytes(Path path) throws IOException

java.util.Scanner is a text scanner. java.util.Scanner是一款文本扫描仪。 That is, the bytes it reads from the input (stdin, say) is expected to comply to a certain charset, usually UTF-8.也就是说，它从输入（例如标准输入）读取的字节应该符合某个字符集，通常是 UTF-8。

In the case of nextByte() , it doesn't read and return a byte as a raw byte directly.在nextByte()的情况下，它不会直接读取并返回一个字节作为原始字节。 Rather, it reads a text and returns the next token as a byte.相反，它读取文本并将下一个标记作为字节返回。 Here's what the documentation of java.util.Scanner.nextByte(radix) says (emphasis added by me):这是java.util.Scanner.nextByte(radix)的文档所说的（重点由我添加）：

If the next token matches the Integer regular expression defined above then the token is converted into a byte value as if by removing all locale specific prefixes, group separators, and localespecific suffixes, then mapping non-ASCII digits into ASCIIdigits via Character.digit, prepending anegative sign (-) if the locale specific negative prefixes and suffixes were present, and passing the resulting string to Byte.parseByte with thespecified radix.如果下一个标记与上面定义的 Integer 正则表达式匹配，则该标记被转换为字节值，就像通过删除所有区域设置特定前缀、组分隔符和区域设置特定后缀，然后通过 Character.digit 将非 ASCII 数字映射为 ASCII 数字，前置如果存在特定于语言环境的负前缀和后缀，则为负号 (-)，并将结果字符串传递给具有指定基数的 Byte.parseByte。

So, what you will have to do is to read as string and convert it to bytes using the right charset (UTF-8, usually).因此，您需要做的是读取字符串并使用正确的字符集（通常为 UTF-8）将其转换为字节。