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Char Array to Byte array conversion and convert back again to char Arrray

Tom Cruser 1685 14-Jan-2016
I want to convert a Java char array to a byte array without creating an intermediate String,since the char array contains a password. I've used a couple of methods, but they all found useless :

char[] password = "password".toCharArray();
byte[] passwordBytes1 = new byte[password.length*2];
ByteBuffer.wrap(passwordBytes1).asCharBuffer().put(password);
byte[] passwordBytes2 = new byte[password.length*2];
for(int i=0; i<password.length; i++) {
    passwordBytes2[2*i] = (byte) ((password[i]&0xFF00)>>8); 
    passwordBytes2[2*i+1] = (byte) (password[i]&0x00FF); 
}
String passwordAsString = new String(password);
String passwordBytes1AsString = new String(passwordBytes1);
String passwordBytes2AsString = new String(passwordBytes2);
System.out.println(passwordAsString);
System.out.println(passwordBytes1AsString);
System.out.println(passwordBytes2AsString);
assertTrue(passwordAsString.equals(passwordBytes1) || passwordAsString.equals(passwordBytes2));

The assertion always fails (and, critically, when the code is used in production, the password is rejected), yet the print statements print out password three times. Why are passwordBytes1AsString and passwordBytes2AsString different from passwordAsString, yet appear identical? Am I missing out a null terminator or something? What can I do to make the conversion and unconversion work?
android android  array 
Updated on 27-Jun-2023
Tom Cruser

Tom Cruser

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2 Answers

Aryan Kumar

Aryan Kumar

27-Jun-2023

Sure, here is how to convert a char array to a byte array and back again to a char array:

Code snippet

import java.nio.charset.StandardCharsets;

public class CharArrayToByteArray {

    public static void main(String[] args) {
        // Create a char array.
        char[] charArray = "Hello, world!".toCharArray();

        // Convert the char array to a byte array.
        byte[] byteArray = StandardCharsets.UTF_8.encode(charArray);

        // Convert the byte array back to a char array.
        char[] newCharArray = StandardCharsets.UTF_8.decode(byteArray).toCharArray();

        // Print the new char array.
        System.out.println(newCharArray);
    }
}

In this code, we first create a char array with the string "Hello, world!". Then, we use the StandardCharsets.UTF_8.encode() method to convert the char array to a byte array. The StandardCharsets.UTF_8.encode() method takes a char array as input and returns a byte array. The byte array contains the UTF-8 encoding of the char array.

Next, we use the StandardCharsets.UTF_8.decode() method to convert the byte array back to a char array. The StandardCharsets.UTF_8.decode() method takes a byte array as input and returns a char array. The char array contains the characters that were encoded in the byte array.

Finally, we print the new char array.

Anonymous User

Anonymous User

14-Jan-2016
The problem is your use of the String(byte[]) constructor, which uses the platform default encoding. That's almost never what you should be doing - if you pass in "UTF-16" as the character encoding to work, your tests will probably pass. Currently I suspect that passwordBytes1AsString and passwordBytes2AsString are each 16 characters long, with every other character being U+0000

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