Recursion method in Java

Question

I am trying to use a recursive method to change strings to char arrays but i am getting an error

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1
    at java.lang.String.substring(Unknown Source)

I want to solve this problem only using recursive method(not loop or toChar method)

public class Recur {
    public char[]  stringTochar(String str)
    {
        if (str != null && str.length() > 0)
        {
            System.out.println(str.charAt(0)) ;
            stringTochar(str.substring(1)); 
        }
        return stringTochar(str.substring(1)) ;
    }
}

public class Tester {
    public static void main(String[] args) {
        Recur recur= new Recur ();
        recur.stringTochar("this is a test");
    }
}

Why are you trying to reinvent String#toCharArray, and in particular, why reinvent it using recursion? — T.J. Crowder
– T.J. Crowder, Commented Feb 10, 2013 at 15:24
Your base case also calls the recursive function instead of stopping. — Makoto
– Makoto, Commented Feb 10, 2013 at 15:25
@ buni: This problem is particularly poorly-suited to being solved with recursion. If you want to learn about recursion, I suggest a different task, such as (say) traversing a tree structure. The problem being that a recursive task must build up its results incrementally, which is difficult to do with a char[] return type. — T.J. Crowder
– T.J. Crowder, Commented Feb 11, 2013 at 12:29

m0skit0 · Accepted Answer · 2013-02-10 15:30:41Z

4

str.substring(1);

What happens when str is length 0?

edited Feb 10, 2013 at 15:30

answered Feb 10, 2013 at 15:24

m0skit0

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Mikhail Vladimirov · Accepted Answer · 2013-02-10 15:37:15Z

1

public class Recur
{
    private static char [] stringToChar (
        String str, char [] destination, int offset)
    {
        if (destination == null)
        {
            destination = new char [str.length ()];
            offset = 0;
        }

        if (offset < str.length ())
        {
            destination [offset] = str.charAt (offset);
            stringToChar (str, destination, offset + 1);
        }
        return destination;
    }

    public static void main (String [] args)
    {
        char [] chars = stringToChar ("this is a test", null, 0);

        for (char c: chars)
            System.out.println (c);
    }
}

edited Feb 10, 2013 at 15:37

answered Feb 10, 2013 at 15:30

Mikhail Vladimirov

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