I was working on this for a while and did not find anything about this on here, so I thought I would post my solution for criticism/usefulness.
import java.lang.*;
public class Concat
{    
    public static void main(String[] args)
    {
        byte[] buf = new byte[256];
        int lastGoodChar=0;
        //fill it up for example only
        byte[] fillbuf=(new String("hello").getBytes());
        for(int i=0;i<fillbuf.length;i++) 
                buf[i]=fillbuf[i];
        //Now remove extra bytes from "buf"
        for(int i=0;i<buf.length;i++)
        {
                int bint = new Byte(buf[i]).intValue();
                if(bint == 0)
                {
                     lastGoodChar = i;
                     break;
                }
        }
        String bufString = new String(buf,0,lastGoodChar);
        //Prove that it has been concatenated, 0 if exact match
        System.out.println( bufString.compareTo("hello"));
    }    
}
                We can convert the byte array to String for the ASCII character set without even specifying the character encoding. The idea is to pass the byte[] to the string.
There are two ways to convert byte array to String: By using String class constructor. By using UTF-8 encoding.
I believe this does the same thing:
String emptyRemoved = "he\u0000llo\u0000".replaceAll("\u0000.*", "");
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