Java使用哪种编码从给出的unicode数据创建字符串？

Question

I am quite perplexed on why I should not be encoding unicode text with UTF-8 for comparison when other text(to compare) has been encoded with UTF-8?

I wanted to compare a text(= アクセス拒否 - means Access denied) stored in external file encoded as UTF-8 with a constant string stored in a .java file as

public static final String ACCESS_DENIED_IN_JAPANESE = "\u30a2\u30af\u30bb\u30b9\u62d2\u5426"; // means Access denied 

The java file was encoded as Cp1252.

I read the file as as input stream by using below code. Point to note that I am using UTF-8 for encoding.

 InputStream in = new FileInputStream("F:\\sample.txt");
        int b1; 
        byte[] bytes = new byte[4096];
        int i = 0;
        while (true) {
            b1 = in.read();
            if (b1 == -1)
                break;
            bytes[i++] = (byte) b1;
        }

        String japTextFromFile = new String(bytes, 0, i, Charset.forName("UTF-8"));

Now when I compare as

System.out.println(ACCESS_DENIED_IN_JAPANESE.equals(japTextFromFile));  // result is `true` , and works fine

but when I encode ACCESS_DENIED_IN_JAPANESE with UTF-8 and try to compare it with japTextFromFile result is false . The code is

String encodedAccessDenied = new String(ACCESS_DENIED_IN_JAPANESE.getBytes(),Charset.forName("UTF-8"));

System.out.println(encodedAccessDenied .equals(japTextFromFile));  // result is `false`

So my doubt is why above comparison is failing, when both the strings are same and have been encoded with UTF-8? The result should be true .

However, in first case, when compared different encoded strings- one with UTF-16(Java default way of encoding string) and other with UTF-8 , result is true , which I think should be false as it is different encoding ,no matter text we read, is same.

Where I am wrong in my understanding? Any clarification is greatly appreciated.

Answer 1

ACCESS_DENIED_IN_JAPANESE.getBytes() does not use UTF-8. It uses your platform's default charset. But then you use UTF-8 to turn those bytes back into a String. This gets you a different String to the one you started with.

Try this:

String encodedAccessDenied = new String(ACCESS_DENIED_IN_JAPANESE.getBytes(StandardCharsets.UTF_8),StandardCharsets.UTF_8
);

System.out.println(encodedAccessDenied .equals(japTextFromFile));  // result is `true`

Answer 2

The best way I know is put all static texts into a text file encoded with UTF-8. And then read those resources with FileReader , setting encoding parameter to "UTF-8"