Thread: Homework: Point me in the right direction?

Hey guys!! I am taking Java and I have a programming assignment that I don't understand. We just started talking about stacks so I'm not sure how to even begin, if someone could help. I'll post the assignment instructions below. Thanks in advance!!


Instructions:
For this assignment, you are to develop a SmartString class that supports insert into a string, delete a substring from a string, and an undo method. Your SmartString class must conform to (implement) the following interface:

public interface SmartStringInterface {
public void insert(int pos, String sstring);
public void delete(int pos, int count);
public void undo();
public String toString();
}

You must use a Stack to store the operations in order to support undo operations. Note that multiple undo operations can be performed in sequence. Using the Java API Stack is fine or you can use ArrayStack from the textbook. Design a class to hold the required information to be placed onto the stack. Only the changes should be stored and not the whole string. You should write a driver program to instantiate a SmartString and thoroughly test your methods. A portion of your grade will be based on how well you test your SmartString class. You should handle stack underflow, but you can assume that the driver will not have any Index out of Bounds errors.

I'm just completely confused on exactly what I'm supposed to be doing. My previous java teacher really didn't teach us a lot so some of us are behind with this class compared to others. I know what implementing the interface means and stuff, but not sure exactly what the SmartString is supposed to be doing.

How does the Stack part work? I think that is throwing a wrench into how I'm understanding it, and I want to make sure I have the right idea.

What would the count be referring to? I understand the concepts of push and pop, but not sure what the point of this program is to do. I think if I can understand it, I might be able to do it even with the stack.

Any way to give me an example of this? I know how the push and pop work and how to set those up. Is insert and delete the same as those 2? If so, where do the count and pos come from? I know they will be the values taken in by those methods, but not sure what they're supposed to represent and where you get them from.

For insert and delete, is the easiest way to do it is StringBuilder?

--- Update ---

Here are my insert and delete methods. I commented the changes part out since that is how I was storing the new string in the stack, but it's wrong. So the deleting and inserting themselves should be correct since my string is string, the substring I'm inserting is sstring (which I hard code into the driver) and pos is the position in the string that the substring is inserted or deleted (which I also hard code when I list the sub strings)

public void insert(int pos, String sstring)
	{
		string.insert(pos, sstring);
		//changes.push(string.toString());
	}
 
	public void delete(int pos, int count) 
	{
		string.delete(pos, count);
		//changes.push(string.toString());
	}