Converting a C-ctyle string encoded as a character array to a Java String

Question

I have a C-style string encoded as an array of characters in Java, but I would like to convert this array to a Java String. I tried using the matching constructor call,

String toRet = new String(new char[]{'B','A','D','\0', 'G', 'A', 'R', 'B', 'A', 'G', 'E'});
System.out.println(Arrays.toString(toRet.toCharArray()));

But the result is incorrect, and in fact oddly buggy. Here's what the above code outputs:

[B, A, D,

And here's what I want

[B, A, D]

I'm running on openJdk6 on Ubuntu. I haven't tested the above code on other VM's.

You perhaps can have a look to [this:][1] [1]: stackoverflow.com/questions/1487023/… — Alain BUFERNE
– Alain BUFERNE, Commented Oct 23, 2012 at 9:52

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

There is no need for a String to get involved here. Just copy into a new array that is one char shorter than your input array. The method to use for this task is Arrays.copyOf.

The reason your output is buggy is because strings in Java have nothing to do with null-terminators. Your first line of code creates a string whose last character is the null-character.

Response to your updated question

If you have garbage following the null-char, you can use new String(inputArray), then find the null-char with String.indexOf('\0') and use that in a String.substring operation to cut out the unneeded part. However, it would be still simpler (from the time/space complexity perspective) to just iterate over the array to locate the null-char and then use Arrays.copyOf with that index as cutoff point.

edited Jun 20, 2020 at 9:12

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answered Oct 23, 2012 at 9:42

Marko Topolnik

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2 Comments

Ben Braun Over a year ago

Modified question to clarify.

Ben Braun Over a year ago

O.K. It, so it takes a few steps, but that's fine. I'll mark this as an accepted answer whenever the system lets me.

Yasin Bahtiyar · Accepted Answer · 2012-10-23 09:50:49Z

0

You can use trim() to remove space chars:

System.out.println(Arrays.toString(toRet.trim().toCharArray()));

answered Oct 23, 2012 at 9:50

Yasin Bahtiyar

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2 Comments

Ben Braun Over a year ago

This works when the null terminator character ends the string, but not when there are garbage characters after the null terminator I want to ignore. Cool trick though, I didn't know trim() also removes \0's at the end.

Ian Roberts Over a year ago

trim() defines whitespace as \u0000 to \u0020 inclusive - it does not use the Unicode definition of whitespace, nor Character.isWhitespace.

Udo Klimaschewski · Accepted Answer · 2012-10-23 11:40:47Z

0

To confuse people that have to maintain your code, you could write:

char[] dta = new char[]{'B','A','D','\0', 'G', 'A', 'R', 'B', 'A', 'G', 'E'};

String string = (dta[0] == '\0') ? "" : (new String(dta)).split("\0")[0];
System.out.println(string.toCharArray());

edited Oct 23, 2012 at 11:40

answered Oct 23, 2012 at 10:17

Udo Klimaschewski

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2 Comments

Ben Braun Over a year ago

This doesn't work. "\0".split("\0")[0] throws IndexOutOfBoundsException

Udo Klimaschewski Over a year ago

Indeed, so what should the resulting String contain in that case? To avoid another line of code: String string = dta[0] == '\0' ? "" : (new String(dta)).split("\0")[0];

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