Java Byte Array to String to Byte Array

Question

You can't just take the returned string and construct a string from it... it's not a byte[] data type anymore, it's already a string; you need to parse it. For example :

String response = "[-47, 1, 16, 84, 2, 101, 110, 83, 111, 109, 101, 32, 78, 70, 67, 32, 68, 97, 116, 97]";      // response from the Python script

String[] byteValues = response.substring(1, response.length() - 1).split(",");
byte[] bytes = new byte[byteValues.length];

for (int i=0, len=bytes.length; i<len; i++) {
   bytes[i] = Byte.parseByte(byteValues[i].trim());     
}

String str = new String(bytes);

** EDIT **

You get an hint of your problem in your question, where you say "Whatever I seem to try I end up getting a byte array which looks as follows... [91, 45, ...", because 91 is the byte value for [, so [91, 45, ... is the byte array of the string "[-45, 1, 16, ..." string.

The method Arrays.toString() will return a String representation of the specified array; meaning that the returned value will not be a array anymore. For example :

byte[] b1 = new byte[] {97, 98, 99};

String s1 = Arrays.toString(b1);
String s2 = new String(b1);

System.out.println(s1);        // -> "[97, 98, 99]"
System.out.println(s2);        // -> "abc";

As you can see, s1 holds the string representation of the array b1, while s2 holds the string representation of the bytes contained in b1.

Now, in your problem, your server returns a string similar to s1, therefore to get the array representation back, you need the opposite constructor method. If s2.getBytes() is the opposite of new String(b1), you need to find the opposite of Arrays.toString(b1), thus the code I pasted in the first snippet of this answer.

String coolString = "cool string";

byte[] byteArray = coolString.getBytes();

String reconstitutedString = new String(byteArray);

System.out.println(reconstitutedString);

That outputs "cool string" to the console.

It's pretty darn easy.

What I did:

return to clients:

byte[] result = ****encrypted data****;

String str = Base64.encodeBase64String(result);

return str;

receive from clients:

 byte[] bytes = Base64.decodeBase64(str);

your data will be transferred in this format:

OpfyN9paAouZ2Pw+gDgGsDWzjIphmaZbUyFx5oRIN1kkQ1tDbgoi84dRfklf1OZVdpAV7TonlTDHBOr93EXIEBoY1vuQnKXaG+CJyIfrCWbEENJ0gOVBr9W3OlFcGsZW5Cf9uirSmx/JLLxTrejZzbgq3lpToYc3vkyPy5Y/oFWYljy/3OcC/S458uZFOc/FfDqWGtT9pTUdxLDOwQ6EMe0oJBlMXm8J2tGnRja4F/aVHfQddha2nUMi6zlvAm8i9KnsWmQG//ok25EHDbrFBP2Ia/6Bx/SGS4skk/0couKwcPVXtTq8qpNh/aYK1mclg7TBKHfF+DHppwd30VULpA== 

What Arrays.toString() does is create a string representation of each individual byte in your byteArray.

Please check the API documentation Arrays API

To convert your response string back to the original byte array, you have to use split(",") or something and convert it into a collection and then convert each individual item in there to a byte to recreate your byte array.

Its simple to convert byte array to string and string back to byte array in java. we need to know when to use 'new' in the right way. It can be done as follows:

byte array to string conversion:

byte[] bytes = initializeByteArray();
String str = new String(bytes);

String to byte array conversion:

String str = "Hello"
byte[] bytes = str.getBytes();

For more details, look at: http://evverythingatonce.blogspot.in/2014/01/tech-talkbyte-array-and-string.html

The kind of output you are seeing from your byte array ([B@405217f8) is also an output for a zero length byte array (ie new byte[0]). It looks like this string is a reference to the array rather than a description of the contents of the array like we might expect from a regular collection's toString() method.

As with other respondents, I would point you to the String constructors that accept a byte[] parameter to construct a string from the contents of a byte array. You should be able to read raw bytes from a socket's InputStream if you want to obtain bytes from a TCP connection.

If you have already read those bytes as a String (using an InputStreamReader), then, the string can be converted to bytes using the getBytes() function. Be sure to pass in your desired character set to both the String constructor and getBytes() functions, and this will only work if the byte data can be converted to characters by the InputStreamReader.

If you want to deal with raw bytes you should really avoid using this stream reader layer.