Stacks for implementing back command!

Question

This here is my Game class, everything works, but im trying to implement a back command by using stacks. I have imported stacks in and all that...The problem im having is that when i go into another room it adds the room in, but im trying to pop it from another method. Iv seen examples of popping within the same method but not from another method.
private void goRoom(Command command)
        if(!command.hasSecondWord())
            // if there is no second word, we don't know where to go...
            System.out.println("Go where?");
            return;
        String direction = command.getSecondWord();
        // Try to leave current room.
        Room nextRoom = currentRoom.nextRoom(direction);
        if (nextRoom == null)
            System.out.println("There is no door!");
        else
            Stack stack = new Stack();
            currentRoom = nextRoom;
            System.out.println(currentRoom.longDescription());
            stack.push(currentRoom);              <<<<<<<<<<<<<<<<<<-----As seen here the currentRoom gets pushed in....but i need to pop out which im trying to do below
    private void goBack(Command command)
        if(previousRoom == null) {
            System.out.println("Sorry, cannot go back!");
            return;
        if(command.hasSecondWord()) {
            // if there is a second word, we cannot go back...
            System.out.println("I don't know what you mean...");
            return;
            stack.pop(); <<<<<<<<<<<<<<<<<<<<<<<<<<-------------- I cant get that syntax to access the above method and make them work togeather. It works within the same method, but 2 differnet methods its having a problem. Can someone give me the correct
            currentRoom = previousRoom;                     syntax so i can use that to pop it out from a different method. Thanks alot much appriciated!             
            System.out.println(currentRoom.longDescription()); //print method where you are
    }

Answer 1

Because stack is now an instance variable, its scope is for the whole class. That means, every method has direct access to it. So, both goRoom and goBack methods will work on the same variable.
I'll suggest to read about variable scoping in java.
Now that the variable is an instance variable, in an application, this could easily lead to multi-threading synchronization problems, if your application is multi-threaded.
So I'll wrap my stack operations in a synchronize block:
synchronize
   stack.push (obj);
}and
synchronize
   stack.pop ();
}