Text editor assignment - using a two stack buffer.

Buffer.java

/*
 * Avindra Goolcharan
 * September 11, 2013
 * CS 216 007 - Data Structures & Algorithms
 * Assignment 2 - Two Stack Buffer
 */
import java.util.Stack;


public class Buffer
{
  private Stack<Character> bufferLeft;
	private Stack<Character> bufferRight;
	
	// necessary when serializing buffer
	private boolean reverse = true;


	// create an empty buffer
	public Buffer()
	{
		bufferLeft = new Stack<Character>();
		bufferRight = new Stack<Character>();
	}
	
	// insert c at the cursor position
	public void insert(char c)
	{
		bufferLeft.push(c);
	}
	
	// delete and return the character at the cursor
	public char delete() 
	{
		return bufferRight.isEmpty() ? '\0' : bufferRight.pop();
	}

	// move the cursor k positions to the left
	public void left(int k)
	{
		while(!bufferLeft.isEmpty() && --k >= 0) bufferRight.push(bufferLeft.pop());
	}
	
	// move the cursor k positions to the right
	public void right(int k)
	{
		while(!bufferRight.isEmpty() && --k >= 0) bufferLeft.push(bufferRight.pop());
	}
	
	// number of characters in the buffer
	public int size()
	{
		return bufferLeft.size() + bufferRight.size();
	}
	
	// class-specific helper function to serialize each buffer
	private String serializeBuffer(Stack<Character> bf)
	{
		int size = bf.size();
		
		StringBuilder out = new StringBuilder();
		if(reverse = !reverse)
		{
			for(int i = size - 1; i>=0; --i)
			{
				out.append(bf.get(i));
			}
		} else {
			for(int i = 0; i < size; ++i)
			{
				out.append(bf.get(i));
			}
		}
		return out.toString();
	}
	
	public String toString()
	{
		return serializeBuffer(bufferLeft) + "•" + serializeBuffer(bufferRight);
	}
}

TextEditor.java

/*
 * Avindra Goolcharan
 * September 11, 2013
 * CS 216 007 - Data Structures & Algorithms
 * Assignment 2 - Text Editing Program
 */
import java.util.Scanner;


public class TextEditor
{

  public static void main(String[] _)
	{
		Buffer textEditor = new Buffer();
		
		Scanner cmd = new Scanner(System.in);
		
		
		// Print instructions

		System.out.println("This is a simple text editor.\n\n"
				+ "\t- '•' represents the location of the cursor.\n"
				+ "\t- Type any character and press enter to add it to the stream.\n"
				+ "\nThe following is a list of commands. "
				+ "\n\n\t+C\tAdd a special character (C) to the stream."
				+ "\n\t-\tRemove a character from the stream."
				+ "\n\t?\tGet information about the stream (i.e., the size)."
				+ "\n\t*\tQuit the text editor"
				+ "\n\t<#\tMove the cursor left by (#) number of places."
				+ "\n\t>#\tMove the cursor right by (#) number of places.\n\n");
		
		while(true)
		{
			System.out.println("\t" + textEditor);
			System.out.print(" > ");
			String command = cmd.nextLine();
			
			char query = command.isEmpty() ? '\0' : command.charAt(0);
			boolean negative = false;
			
			switch(query)
			{
			case '-':
				textEditor.delete();
				break;
			case '?':
				System.out.println("Number of characters: " + textEditor.size());
				break;
			case '*':
				System.out.println("Goodbye!");
				cmd.close();
				return;
			case '<':
				negative = true;
			case '>':
				int arg = new Integer(command.substring(1, command.length()));
				if(negative)
					textEditor.left(arg);
				else
					textEditor.right(arg);
				break;
			case '\0':
				break;
			case '+':
				query = command.charAt(1);
			default:
				textEditor.insert(query);
				break;
			}	
		}
		
	}
}