字符串，带二进制数字到字符串Base64 - JAVA

Question

I'm trying to convert an string with characters to another string in base64. But, unfortunately i have not done it yet.

SO got this String: 11000110 01111111 10011100 10010111 00111101 11001011 01101011 11000110 01010110 10101001 11101010 01111010 10011110 00100001

And it should become: xn+clz3La8ZWqep6niE=

To transform from String Base64 to an string with binary I got it using this code:

public static void main(String[] args)
{
    String s = new String("xlactz3Ja8Z/qep6niE=");

    System.out.println("String: " + s);

    byte[] b = Base64.getDecoder().decode(s);
    String res = "";
    String aux = new String();
    for(byte a : b)
    {
        aux = Integer.toBinaryString(255 & a);

        // If length is less than 8, than add "0"
        if (aux.length() != 8) {
            aux = padronize (aux);
        }

        res = res + aux + " ";
}


// Padronize all Substrings to have length 8
private static String padronize (String str) {
    String aux = "";

    // Create a auxiliar string to padronize
    for (int i = 0; i < 8 - str.length(); i++) {
        aux += "0";
    }

    return aux + str;
}

Answer 1

To convert from base64 string to the binary string your code is right, I wrote it in this way:

public static String fromBase64ToBinaryString(String base64String){
        byte[] b = Base64.getDecoder().decode(base64String);
        String []result = new String[b.length];
        for (int i=0;i<b.length;i++){
            result[i] = String.format("%8s", Integer.toBinaryString(b[i] & 0xFF)).replace(' ', '0');
        }
        return String.join(" ", result);
    }

To convert from binary String to the base64 string you can use this code:

public static String fromBinaryStringToBase64(String binary) {
        String[] split = binary.split(" ");
        byte[] arrayBinary = new byte[split.length];
        for(int i=0;i<split.length;i++){
            arrayBinary[i] = (byte)Integer.parseInt(split[i],2);
        }
        return Base64.getEncoder().encodeToString(arrayBinary);     
    }

here the sample code in order to call the two methods:

String s = "xn+clz3La8ZWqep6niE=";
String fromBase64ToBinaryString = fromBase64ToBinaryString( s);
System.out.println(fromBase64ToBinaryString);

String binary = "11000110 01111111 10011100 10010111 00111101 11001011 01101011 11000110 01010110 10101001 11101010 01111010 10011110 00100001";
String fromBinaryStringToBase64 = fromBinaryStringToBase64(binary);
System.out.println(fromBinaryStringToBase64);