Someone

import java.util.Scanner;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.PrintWriter;

/*Tiffany Miller
 * tmm211
 * February 20 2008
 * The purpose of this program is to define a class that encapsulates the implementation
 * of a stack, use that stack in the applications of previous assignements, and practice
 * arrays.
 */

public class P5
{
  public static void main(String[] args)
  {
    Scanner inputFile = null;
    PrintWriter outputFile = null;
    boolean error = false;
    char operand = ' ';
    String operation = "";
    String line ="";
    int linecounter= 2;
    
    Stack[] Hanoi= new Stack[3];
    
    //The try, catch loops are used to input file hanoi.txt and output 
    //the file to P5.txt.
    try
    {
      inputFile = new Scanner(new FileInputStream("hanoi.txt"));
    }
    
    catch(FileNotFoundException e)
    {
      System.out.println("hanoi.txt was not found or could not be opened");
      System.exit(0);
    }
    
    try
    {
      outputFile = new PrintWriter(new FileOutputStream("P5.txt"));
    }
    catch(FileNotFoundException e)
    {
      System.out.println("P5.txt could not be opened or created");
      System.exit(0);
    }
    
    for( int i = 0; i< Hanoi.length; i++)
      Hanoi[i] = new Stack();
    
    line= inputFile.nextLine();
    Hanoi[0]= new Stack(line);
    
    while ((inputFile.hasNextLine()) && (error == false))
    {
      operation = inputFile.next();
      inputFile.nextLine();
      
      if(operation.equals("push0"))
      {
        if(operand!=' ' && (Hanoi[0].isEmpty() || operand < Hanoi[0].getTop()))       
        {
          Hanoi[0].push(operand);
          operand = ' ';
        }
        else
        {
          outputFile.println("Invalid push at line: " + linecounter +". Letter is too big to be pushed onto stack0");
          error = true;
        }
      }
      else if( operation.equals("push1"))
      {
        System.out.println(operand + " " + Hanoi[1].toString());
        
        if (operand !=' ' && (Hanoi[1].isEmpty() || operand < Hanoi[1].getTop())) 
        {
          Hanoi[1].push(operand);
          operand =' ';
        }
        else
        {
          outputFile.println("Invalid push at line: " + linecounter + ".The letter to be pushed is too big for stack1");
          error = true;
        }
      }
      else if(operation.equals("push2"))
      {
        if(operand !=' ' && (Hanoi[2].isEmpty() || operand < Hanoi[2].getTop()))
        {
          Hanoi[2].push(operand);
          operand =' ';
        }
        else
        {
          outputFile.println("Invalid push at line: " + linecounter + ".The letter to be pushed is too big for stack2");
          error = true;
        }
      }                                        
      else if( operation.equals("pop0") && !Hanoi[0].isEmpty())
      {
        Hanoi[0].pop();
      }
      else if( operation.equals("pop1") && !Hanoi[1].isEmpty())
      {
        Hanoi[1].pop();
      }
      else if( operation.equals("pop2")&& !Hanoi[2].isEmpty())
      {
        Hanoi[2].pop();
      }
      else
      {
        outputFile.println("Invalid pop at line: " + linecounter + ". Stack is empty");
        error= true;
      }
      outputFile.println("operand=" + operand);
      linecounter++;
    }
    outputFile.println("Stack0: " + Hanoi[0].toString());
    outputFile.println("Stack1: " + Hanoi[1].toString());
    outputFile.println("Stack2: " + Hanoi[2].toString());
    
    inputFile.close();
    outputFile.close();
    
  }
}
class Stack
    {
      private String stack;
      
      public Stack () //constructor creates empty stack
      {
        stack = "";
      }
      
      public Stack (String St) //constructor a stack to its initial contents
      {
        stack = St;
      }
      
      public boolean isEmpty () //returns a boolean that says whether there is data in the stack
      {
        if(stack.length() == 0)
          return true;
        else
          return false;
      }
      
      public char getTop () // an accessor that returns the char at the top of the stack
      {
        char operand;
        operand = stack.charAt(0);
        return operand;
      }
      
      public void push (char c) // void method with a char argument that pushes char on stack
      {
       stack = c + stack;
      }
      
      public char pop() // does implementation of pop method, returning a char
      {
        char temp;
        temp = stack.charAt(0);
        stack = stack.substring(1);
        return temp;
      }
      
      public String toString() //needed for printing stack to file
      {
        return stack;
      }
      
      public boolean equals(Stack other) //helps compare two stacks 
      {
        if(stack.equals(other.stack))
          return true;
        else 
          return false;
      }
      }