Converting byte array to String (Java)

By | June 25, 2019

Question

I’m writing a web application in Google app Engine. It allows people to basically edit html code that gets stored as an .html file in the blobstore.

I’m using fetchData to return a byte[] of all the characters in the file. I’m trying to print to an html in order for the user to edit the html code. Everything works great!

Here’s my only problem now:

The byte array is having some issues when converting back to a string. Smart quotes and a couple of characters are coming out looking funky. (?’s or japanese symbols etc.) Specifically it’s several bytes I’m seeing that have negative values which are causing the problem.

The smart quotes are coming back as -108 and -109 in the byte array. Why is this and how can I decode the negative bytes to show the correct character encoding?

Solution

The byte array contains characters in a special encoding (that you should know). The way to convert it to a String is:

String decoded = new String(bytes, "UTF-8");  // example for one encoding type

By The Way – the raw bytes appear may appear as negative decimals just because the java datatype byte is signed, it covers the range from -128 to 127.

-109 = 0x93: Control Code "Set Transmit State"

The value (-109) is a non-printable control character in UNICODE. So UTF-8 is not the correct encoding for that character stream.

0x93 in “Windows-1252” is the “smart quote” that you’re looking for, so the Java name of that encoding is “Cp1252”. The next line provides a test code:

System.out.println(new String(new byte[]{-109}, "Cp1252")); 

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