public class StringNode {
    private char ch;
    private StringNode next;
    
    public StringNode(char c, StringNode n) {
        ch = c;
        next = n;
    }

    public static void toUpperCase(StringNode str) {        
        StringNode trav = str; 
        while (trav != null) {
            trav.ch = Character.toUpperCase(trav.ch); 
            trav = trav.next;
        }
    } 
    
    public static void main(String[] args)  {
        StringNode s1 = new StringNode('t', null);
        s1 = new StringNode('a', s1);
        s1 = new StringNode('c', s1);

        StringNode.toUpperCase(s1);
    }
}