在java中将字符串从一种编码解释为另一种编码

Question

I've looked around for answers to this (I'm sure they're out there), and I'm not sure it's possible.

So, I got a HUGE file that contains the word "för". I'm using RandomAccessFile because I know where it is (kind of) and can therefore use the seek() function to get there.

To know that I've found it I have a String "för" in my program that I check for equality. Here's the problem, I ran the debugger and when I get to "för" what I get to compare is "för".

So my program terminates without finding any "för".

This is the code I use to get a word:

    private static String getWord(RandomAccessFile file) throws IOException {
    StringBuilder stb = new StringBuilder();
    String word;
    char c;
    c = (char)file.read();
    int end;
    do {
        stb.append(c);
        end = file.read();
        if(end==-1)
            return "-1";
        c = (char)end;

    } while (c != ' ');
    word = stb.toString();
    word.trim();
    return word;
}

So basically I return all the characters from the current point in the file to the first ' '-character. So basically I get the word, but since (char)file.read(); reads a byte (I think), UTF-8 'ö' becomes the two characters 'Ã' and '¶'?

One reason for this guess is that if I open my file with encoding UTF-8 it's "för" but if I open the file with ISO-8859-15 in the same place we now have exactly what my getWord method returns: "för"

So my question:

When I'm sitting with a "för" and a "för", is there any way to fix this? Like saying "read "för" as if it was an UTF-8 string" to get "för"?

Answer 1

If you have to use a RandomAccessFile you should read the content into a byte[] first and then convert the complete array to a String - somthing along the lines of:

byte[] buffer = new byte[whatever];
file.read(buffer);
String result = new String(buffer,"UTF-8");

This is only to give you a general impression what to do, you'll have to add some length-handling etc.

This will not work correctly if you start reading in the middle of a UTF-8 sequence, but so will any other method.

Answer 2

You are using RandomAccessFile.read() . This reads single bytes. UTF-8 sometimes uses several bytes for one character.

Different methods to read UTF-8 from a RandomAccessFile are discussed here: Java: reading strings from a random access file with buffered input

If you don't necessarily need a RandomAccessFile, you should definitely switch to reading characters instead of bytes .

If possible, I would suggest Scanner.next() which searches for the next word by default.

Answer 3

import java.nio.charset.Charset;
String encodedString = new String(originalString.getBytes("ISO-8859-15"), Charset.forName("UTF-8"));