public class StringNode {
    private char ch;
    private StringNode next;
    
    public StringNode(char c, StringNode n) {
        ch = c;
        next = n;
    }
    
    private static StringNode getNode(StringNode str, int i) {
        if (i < 0 || str == null) {
            return null;
        } else if (i == 0) {
            return str;
        } else {
            return getNode(str.next, i - 1);
        }
    }
    
    public static StringNode convert(String s) {
        // code to check for empty string goes here
        StringNode firstNode = new StringNode(s.charAt(0), null);
        StringNode prevNode = firstNode;
        StringNode nextNode;
        
        for (int i = 1; i < s.length(); i++) {
            nextNode = new StringNode(s.charAt(i), null);
            prevNode.next = nextNode;
            prevNode = nextNode;
        }
        
        return firstNode;
    }
    
    public static StringNode copy(StringNode str) {
        if (str == null) {
            return null;
        }

        StringNode copyRest = copy(str.next);
        return new StringNode(str.ch, copyRest);    
    }
    
    // for simplicity, this version assumes the inputs are valid
    public static StringNode deleteChar(StringNode str, int i) {
        if (i == 0) {
            str = str.next;
        } else {
            StringNode prevNode = getNode(str, i-1);
            prevNode.next = prevNode.next.next;
        }
        
        return str;
    }
     
    public static void main(String[] args)  {
        StringNode s1 = StringNode.convert("cat");
        StringNode s2 = s1;
        StringNode s3 = StringNode.copy(s1);
        s1 = StringNode.deleteChar(s1, 1);
    }
}