Java: convert binary string to hex string

Question

I need to convert the binary string to a hex string but i have a problem. I converted the binary string to a hex string by this method:

public static String binaryToHex(String bin){
   return Long.toHexString(Long.parseLong(bin,2));
}

it's ok! but I lose the zeros to the left of the string. Ex:

the method return this: 123456789ABCDEF, but i want returned this:

00000123456789ABCDEF

Use `String.format` method to append the `String` with `0's` — Rohit Jain, Oct 21 '13 at 11:59
The reason why you loose them is because leading zero's in a Long have no value. You'll either have to change the way you process your conversion, or you will have to add them again by yourself. The String.format that @RohitJain suggested has my preference as well. — Michaël Benjamin Saerens, Oct 21 '13 at 12:10

score 8 · Accepted Answer · answered Oct 21 '13 at 12:25

Instead of Long.toHexString I would use Long.parseLong to parse the value and then String.format to output the value with the desired width (21 in your example):


public static String binaryToHex(String bin) {
   return String.format("%21X", Long.parseLong(bin,2)) ;
}

score 1 · Answer 2 · answered Oct 21 '13 at 12:15

Not very elegant, but works

public static String binaryToHex(String bin) {
    String hex = Long.toHexString(Long.parseLong(bin, 2));
    return String.format("%" + (int)(Math.ceil(bin.length() / 4.0)) + "s", hex).replace(' ', '0');
}

I've used String.format() to left pad string with whitespaces then called replace() to replace it with zeros.

score 0 · Answer 3 · answered Oct 21 '13 at 12:24

0

Just add the zeros manually. Here's one way:

public static String binaryToHex(String bin){
    return ("0000000000000000" + Long.toHexString(Long.parseLong(bin, 2)).replaceAll(".*.{16}", "$1");
}

answered Oct 21 '13 at 12:24

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Java: convert binary string to hex string

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