Writing Method Symmetric Using Stack And Queue

The question is write to a method symmetric that accepts a stack of integers as a parameter and replaces the stack contents with itself plus a symmetrical version of itself (the same elements in the opposite order).

For example, suppose a variable s stores the following elements:
bottom [10, 50, 19, 54, 30, 67] top

After a call of symmetric(s),the stack would store the following elements
bottom [10, 50, 19, 54, 30, 67, 67, 30, 54, 19, 50, 10] top

Note that the symmetric version is added on to the top of what was originally in the stack. The bottom half of the stack contains the original numbers in the same order.

If your method is passed an empty stack, the result should be an empty stack.
If your method is passed a null stack, your method should throw an IllegalArgumentException.

a) Write the method symmetric using one temporary stack and one temporary queue.
/> Re-write the method using only one temporary Queue.

What I have done so far is

public static Stack symmetric(Stack s1){
Stack s2 =new Stack();
int theTop=0;
if(s1.isEmpty()){
return s1;

[Code] .....

Its not working.