Stacks issue

[misty granite]

public static void stutter(Stack<Integer> st){
    
    
    Stack<Integer> stack = new Stack<Integer>();
    
    Iterator value = st.iterator();
    
    Integer currValue;
    
    while (value.hasNext()) { 
         
            currValue = value.next();
        
            stack.push(currValue);
            stack.push(currValue);
        
        } 
    
    st.addAll(stack);
    
    
}```
so im trying to pop a stack like
1, 2 ,3 ,4
to 1 1 2 2 3 3 4 4
my error is cant convert object to integer
but if i store as an object
it cant convert integer to object

[fair root]

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[real topaz]

you are bound to run into issues with your current approach. Even if you correctly specify your iterator Iterator<Integer> value = st.iterator() , Stack#push will throw a ConcurrentModificationException. You can either create a new Stack object which you will push each element twice or if you really need to use the same object use a simple for-loop. Stack extends Vector so it inherits all methods.