Is it possible to add data to a string after adding “\0” (null)?

Question

I have a string that I am creating, and I need to add multiple \"\\0\" (null) characters to the string. Between each null character, is other text data (Just ASCII alphanume

Answer 1

I strongly suspect this is nothing to do with the text in the string itself - I suspect it's just how it's being displayed. For example, try this:

public class Test {
    public static void main(String[] args) {
        String first = "first";
        String second = "second";
        String third = "third";
        String text = first + "\0" + second + "\0" + third;
        System.out.println(text.length()); // Prints 18
    }
}

This prints 18, showing that all the characters are present. However, if you try to display text in a UI label, I wouldn't be surprised to see only first. (The same may be true in fairly weak debuggers.)

Likewise you should be able to use:

 char c = text.charAt(7);

And now c should be 'e' which is the second letter of "second".

Basically, I'd expect the core of Java not to care at all about the fact that it contains U+0000. It's just another character as far as Java is concerned. It's only at boundaries with native code (e.g. display) that it's likely to cause a problem.

If this doesn't help, please explain exactly what you've observed - what it is that makes you think the rest of the data isn't being appended.

EDIT: Another diagnostic approach is to print out the Unicode value of each character in the string:

for (int i = 0; i < text.length(); i++) {
    System.out.println((int) text.charAt(i));
}

Answer 2

I suggest you use a char[] or List<Char> instead since it sounds like you're not really using a String as such (a real String doesn't normally contain nulls or other unprintable characters).

Answer 3

This is because \ is an escape character in Java (as in many C-related languages) and you need to escape it using additional \ as follows.

String str="\\0Java language";
System.out.println(str);

and you should be able the display \0Java language on the console.

Answer 4

Same behavior for the StringBuffer class?

Since "\0" makes some trouble, I would recommend to not use it. I would try to replace some better delimiter with "\0" when actually writing the string to your DB.