Parse String content to Binary and Then Convert to String in Java

Question

I need to parse String content as binary sequence and convert them to its UTF-8 equivalent String.

For example, UTF-8 binary equivalents of B, A and R are as follows:
B = 01000010
A = 01000001
R = 01010010

Now, I need to convert a string "010000100100000101010010" to string "BAR"
i.e. For above case input string with 24 characters are divided into three equal parts(8 character in each part) and translated to its UTF-8 equivalent as a String value.

Sample Code:

public static void main(String args[]) {
    String B = "01000010";
    String A = "01000001";
    String R = "01010010";
    String BAR = "010000100100000101010010";

    String utfEquiv = toUTF8(BAR);//expecting to get "BAR"
    System.out.println(utfEquiv);
}

private static String toUTF8(String str) {
    // TODO 
    return "";
}

What should be the implementation of method toUTF8(String str){}

@Yesyoor , Updated but you can propose or EDIT. Thanks in advanced — mmuzahid
– mmuzahid, Commented Feb 25, 2022 at 4:15

mmuzahid · Accepted Answer · 2016-02-08 09:20:18Z

4

You should separate this into two problems:

Converting the string into a byte array by parsing the binary values
Converting the byte array back into a string using UTF-8

The latter is very straightforward, using new String(bytes, StandardCharsets.UTF_8).

For the first part, the tricky part is that Byte.parseByte won't automatically handle a leading 1... so I'd probably parse each 8-bit string into a short and then cast to byte:

public static byte[] binaryToBytes(String input) {
    // TODO: Argument validation (nullity, length)
    byte[] ret = new byte[input.length() / 8];
    for (int i = 0; i < ret.length; i++) {
        String chunk = input.substring(i * 8, i * 8 + 8);
        ret[i] = (byte) Short.parseShort(chunk, 2);
    }
    return ret;
}

edited Feb 8, 2016 at 9:20

mmuzahid

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answered Feb 8, 2016 at 7:18

Jon Skeet

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5 Comments

mmuzahid Over a year ago

is it input.length or input.length() and Short.parse(chunk, 2) or Short.parseShort(chunk, 2)? because your code showing compilation error.

Jon Skeet Over a year ago

@mmuzahid: Thanks for the substring fix, too. I always forget which way round Java is - .NET takes the length instead of the end index...

mmuzahid Over a year ago

could you tell me the purpose of radix? I never use this.

Jon Skeet Over a year ago

@mmuzahid: It's to say that it's binary ('1' and '0' characters). If your string contained hex instead, it would be 16 (and you'd use two characters per byte, of course).

Michael-O Over a year ago

Striked again by Jon Skeet!

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