当我将编码设置为UTF-16时，为什么FileInputStream readline返回null？

Question

It works fine with UTF-8 , and it also works fine with UTF-16 if I use different file.

BufferedReader br = new BufferedReader(new InputStreamReader(new 
FileInputStream(filePath), "UTF-16"));

If I replace UTF-16 with UTF-8 in above code, everything works as expected, why is that?

Suggested answer is different because I just need to read the file. Answer was simple, I can't read UTF-16 if the file is UTF-8.

Answer 1

Check the encoding of your files. UTF-16 can be encoded using Big Endian (UTF-16BE) or Little Endian (UTF-16LE). These are different.

This code works for four variants of the same file.

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;

public class SOPlayground {

    public static void main(String[] args) throws Exception {
        readAndPrint("/tmp/u-8.txt", Charset.forName("UTF-8"));
        readAndPrint("/tmp/u-16.txt", Charset.forName("UTF-16"));
        readAndPrint("/tmp/u-16le.txt", Charset.forName("UTF-16LE"));
        readAndPrint("/tmp/u-16be.txt", Charset.forName("UTF-16BE"));
    }

    private static void readAndPrint(String filePath, final Charset charset) throws IOException, FileNotFoundException {
        final BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(filePath), charset));
        String line = br.readLine();
        while (line != null) {
            System.out.println(line);
            line = br.readLine();
        }
    }
}

On GNU/Linux you can check the encoding using the file tool:

/tmp % file u*.txt
u-16be.txt: data
u-16le.txt: data
u-16.txt:   Little-endian UTF-16 Unicode text, with no line terminators
u-8.txt:    UTF-8 Unicode text

The content of these files are all different:

/tmp % cat u*.txt
����
����
������
üäöü

But using the above Java code, they can be read correctly. The output of my Java code is:

üäöü
üäöü
üäöü
üäöü