Need help with a few Java questions, If anyone could please help.

[DigitalBullets]

I have two questions that I cannot figure out how to code the method for. I understand what the question is asking for and the entire process from beginning to end along with how stack and queue works. My problem is that I do not know that actual code well. I am a beginner to java, if someone could please help me with the physical code and maybe put a side note like this line of code does this or that. I would really appreciate it, it would help me learn the code itself.

Thank you!

First question, that I cannot figure out the method for is:

In the lectures we use the data structures “ArrayStack” and “ArrayQueue” to write a Java program to decide if an input string is a palindrome. We also use the data structures “LinkedStack” and “LinkedQueue” to write a Java program to decide if an input string is a palindrome. You are asked to use the data structures “ArrayStack” and “LinkedQueue” to write a Java program testing if an input string is a palindrome.

I understand how ArrayStack and LinkedQueue work, just not the code to solve this problem.

Second Question, that I cannot figure out the method for is:

Using either “ArrayStack” or “LinkedStack”, write a Java program to decide if an input string containing the character ‘$’ exactly once is in the following set.

L = {An$Bn: where An = AA … A (there are n copies of A), Bn = BB … B (there are n copies of B, and n ≥ 0. When n = 0, both An and Bn are empty strings}.


Acceptable answers are $, A$B, AA$BB, AAA$BBB, and so on
Unacceptable answers are A$BB, AA$B, a$b, and so on


If you can possibly help me I would really appreciate it. Thank you for your time.

[Wnt2bsleepin]

can you post the code?

[DigitalBullets]

can you post the code?

That is what I dont have. I dont know how program the methods to solve this problem. All I have right is the code for the interfaces of ArrayStack, ArrayQueue, LinkedStack, and LinkedQueue, and some other basic functions that are not the ones that I need. If you would Like I can still post the that code, but I dont know if it will help. Ill go get it.

[DigitalBullets]

can you post the code?

This is the backbone that I am using.

import javax.swing.JOptionPane;

public class TestArrayStackArrayQueue
{
	public static void main(String args[])
	{
	  System.out.println("Creating a stack of size 3");

	  ArrayStack s1 = new ArrayStack(3);

	  System.out.println("Is empty " + s1.isEmpty());

	  System.out.println("Is full " + s1.isFull());

	  System.out.println();
	  System.out.println();

	  String cmd;


	  cmd = JOptionPane.showInputDialog(
"a for pop; b for top; c for push strings; d for push any instance of objects; "
 + "e for displaying in reversal order; " + " p for checking palindrome." +
 " pp for cheching palindrome (ArrayQueue1); " +
 " ppp for cheching palindrome (ArrayQueue2); ");

	  if(cmd.equals("a"))
	    s1.pop();

	  if (cmd.equals("b"))
	    System.out.println(s1.top());

	  if (cmd.equals("c"))
	  {
	  	String cmd1;
	    cmd1 = JOptionPane.showInputDialog(
            "2 for entering two stings; 3 for entering three strings");

        if (cmd1.equals("2"))
        {for(int i = 1; i<= 2; i++)
           {String str1 = JOptionPane.showInputDialog(
         	"enter the string" + i + " and push it on the stack");
             s1.push(str1);
           }

         System.out.println("Is empty " + s1.isEmpty());

	     System.out.println("Is full " + s1.isFull());


         System.out.println("The top element is " + s1.top());

         s1.pop();
         System.out.print("After one pop, the top element is ");
         System.out.println(s1.top());
         }
         if (cmd1.equals("3"))
          {for(int i = 1; i<= 3; i++)
           {String str2 = JOptionPane.showInputDialog(
         	"enter the string" + i + " and push it on the stack");
             s1.push(str2);
           }

         System.out.println("Is empty " + s1.isEmpty());

	     System.out.println("Is full " + s1.isFull());

         System.out.println("The top element is " + s1.top());

         String item = JOptionPane.showInputDialog(
            "entering a string to be pushed onto the stack");
         s1.push(item);
         }
        }

         if (cmd.equals("d"))
         {

         System.out.println("Create another stack of size 10");
         ArrayStack s = new ArrayStack(10);


         System.out.println("enter instance <10> of Integer on the stack");

         Integer Int1 = new Integer(10);
         s.push(Int1);

         System.out.println("enter instance <20.0> of Double on the stack");

         Double double1 = new Double(20.0);
         s.push(double1);

         System.out.println("enter instance <$> of Character on the stack");

         Character char1 = new Character('$');
         s.push(char1);


       System.out.println("enter instance <Yao, 226> of NBA Star on the stack");

         Star star1 = new Star ("Yao", 226);
         s.push(star1);

       System.out.println("enter instance of Circle on the stack");

         Circle cir1 = new Circle(10.0, 4.0, 7.0);
         s.push(cir1);

         System.out.println("top and pop the elements on the stack");

         System.out.println("The first one is a circle");
         Circle c1 = (Circle)(s.top());


         System.out.println("Radius " + c1.radius);

         System.out.println("X coordinate " + c1.centerX);
         System.out.println("Y coordinate " + c1.centerY);

         System.out.println("Area " + c1.findArea());
         s.pop();


         System.out.println("The second one is a NBA star");
         Star st1 = (Star)(s.top());

         System.out.println("Name " + st1.Name);
         System.out.println("Height " + st1.height);
         s.pop();


         System.out.println("The third one is a character");
         Character ch1 = (Character)(s.top());
         System.out.println("The character is " + ch1.charValue());
         s.pop();


         System.out.println("The 4th one is a double number");
         Double d1 = (Double)(s.top());
         System.out.println("The double number is " + d1.doubleValue());
         s.pop();


         System.out.println("The 5th one is an integer number");
         Integer i1 = (Integer)(s.top());
         System.out.println("The integer number is " + i1.intValue());
         s.pop();

        }

     if (cmd.equals("e"))
     {
     	String str10 = JOptionPane.showInputDialog(
         	"enter a string and I will use the stack to display it in "
         	+ "reversal order");

            ArrayStack s10 = new ArrayStack(200);
          for (int k = 0; k < str10.length(); k++)
             s10.push(new Character (str10.charAt(k)));

          while(!s10.isEmpty())
     	  {
     	  	 Character ch10 = (Character)(s10.top());
     	     System.out.println(ch10.charValue());
     	     s10.pop();

     	   }
      }

     if (cmd.equals("p"))
     {
     	String str20 = JOptionPane.showInputDialog(
         	"enter a string and I will use the stack to check if it "
         	+ "is a palindrome");

            ArrayStack s20 = new ArrayStack(200);

          for (int k = 0; k < str20.length(); k++)
             s20.push(new Character (str20.charAt(k)));

          boolean bb = true;

          for (int u = 0; u < str20.length(); u++)
     	  {

     	  	 Character ch20 = (Character)(s20.top());
     	      s20.pop();

     	     if (ch20.charValue() != str20.charAt(u))
     	        {
     	           bb = false;
     	           break;
     	        }

     	   }

         System.out.println(str20 + " is a palindrome: " + bb);
      }


      if (cmd.equals("pp"))
     {
     	String str20 = JOptionPane.showInputDialog(
         	"enter a string and I will use the stack and queue1 to check if it "
         	+ "is a palindrome");

            ArrayStack s20 = new ArrayStack(200);
            ArrayQueue1 q20 = new ArrayQueue1(200);

          for (int k = 0; k < str20.length(); k++)
            { s20.push(new Character (str20.charAt(k)));
              q20.enqueue(new Character (str20.charAt(k)));
            }


          boolean bb = true;

          for (int u = 0; u < str20.length(); u++)
     	  {

     	  	 Character ch20 = (Character)(s20.top());
     	      s20.pop();
     	      Character qq20 = (Character)(q20.dequeue());


     	     if (ch20.charValue() != qq20.charValue())
     	        {
     	           bb = false;
     	           break;
     	        }

     	   }

         System.out.println(str20 + " is a palindrome: " + bb);
      }


     if (cmd.equals("ppp"))
     {
     	String str20 = JOptionPane.showInputDialog(
         	"enter a string and I will use the stack and queue2 to check if it "
         	+ "is a palindrome");

            ArrayStack s20 = new ArrayStack(200);
            ArrayQueue2 q20 = new ArrayQueue2(200);

          for (int k = 0; k < str20.length(); k++)
            { s20.push(new Character (str20.charAt(k)));
              q20.enqueue(new Character (str20.charAt(k)));
            }


          boolean bb = true;

          for (int u = 0; u < str20.length(); u++)
     	  {

     	  	 Character ch20 = (Character)(s20.top());
     	      s20.pop();
     	      Character qq20 = (Character)(q20.dequeue());



     	     if (ch20.charValue() != qq20.charValue())
     	        {
     	           bb = false;
     	           break;
     	        }

     	   }

         System.out.println(str20 + " is a palindrome: " + bb);
      }



   }

}


class Star

{
   String Name;
   int height;

   Star (String name, int h)
   {
       Name = new String(name);
       height = h;
   }
}


class Circle {
  double radius;
  double centerX;
  double centerY;

  Circle(double r, double x, double y)
  {
  	radius = r;
  	centerX = x;
  	centerY = y;
  }

  /** Return the area of this circle */
  double findArea() {
    return radius * radius * 3.14159;
  }
}

 interface StackInterface

{
  public void push(Object item) throws StackOverflowException;
  // Effect:         Adds item to the top of this stack.
  // Postcondition:  If (this stack is full)
  //                    an unchecked exception that communicates
  //                    'push on stack full' is thrown
  //                 else
  //                    item is at the top of this stack.

  public void pop() throws StackUnderflowException;
  // Effect:         Removes top item from this stack
  // Postconditions: If (this stack is empty)
  //                   an unchecked exception that communicates
  //                   'pop on stack empty' is thrown
  //                 else
  //                   top element has been removed from this stack.

  public Object top() throws StackUnderflowException;
  // Effect:         Returns a reference to the element on top of this stack
  // Postconditions: If (this stack is empty)
  //                    an unchecked exception that communicates
  //                   'top on stack empty' is thrown
  //                 else
  //                   return value = (top element of this stack).

  public boolean isEmpty();
  // Effect:         Determines whether this stack is empty.
  // Postcondition:  Return value = (this stack is empty)

  public boolean isFull();
  // Effect:         Determines whether this stack is full.
  // Postcondition:  Return value = (stack is full)
}


//public
class StackOverflowException extends RuntimeException
{
  public StackOverflowException()
  {
  }

  public StackOverflowException(String message)
  {
    super(message);
  }
}


//public
class StackUnderflowException extends RuntimeException
{
  public StackUnderflowException()
  {
  }

  public StackUnderflowException(String message)
  {
    super(message);
  }
}


class ArrayStack implements StackInterface
{
  private Object[] stack;           // Array that holds stack elements
  private int topIndex = -1;        // index of top element in stack

  // Constructors
  public ArrayStack()
  {
    stack = new Object[100];
  }

  public ArrayStack(int maxSize)
  {
    stack = new Object[maxSize];
  }

  public void push(Object item)
  // Adds an element to the top of this stack
  {
    if (!isFull())
    {
      topIndex++;
      stack[topIndex] = item;
    }
    else
      throw new StackOverflowException("Push attempted on a full stack.");
  }

  public void pop()
  // Removes an element from the top of this stack
  {
    if (!isEmpty())
    {
      stack[topIndex] = null;
      topIndex--;
    }
    else
      throw new StackUnderflowException("Pop attempted on an empty stack.");
  }

  public Object top()
  // Returns the element on top of this stack
  {
    Object topOfStack = null;
    if (!isEmpty())
      topOfStack = stack[topIndex];
    else
      throw new StackUnderflowException("Top attempted on an empty stack.");
    return topOfStack;
  }

  public boolean isEmpty()
  // Checks if this stack is empty
  {
    if (topIndex == -1)
      return true;
    else
      return false;
  }

  public boolean isFull()
  // Checks if this stack is full
  {
    if (topIndex == (stack.length - 1))
      return true;
    else
      return false;
  }
}


interface QueueInterface

{
  public void enqueue(Object item);
  // Effect:         Adds item to the rear of this queue.
  // Precondition:   This queue is not full.
  // Postcondition:  item is at the rear of this queue.

  public Object dequeue();
  // Effect:         Removes front element from this queue and returns it.
  // Precondition:   This queue is not empty.
  // Postconditions: Front element has been removed from this queue.
  //                 Return value = (the removed element)

  public boolean isEmpty();
  // Effect:         Determines whether this queue is empty.
  // Postcondition:  Return value = (this queue is empty)

  public boolean isFull();
  // Effect:         Determines whether this queue is full.
  // Postcondition:  Return value = (queue is full)
}



class ArrayQueue1 implements QueueInterface
{
  private Object[] queue;           // Array that holds queue elements
  private int capacity;             // size of the array (capacity of the queue)
  private int numItems = 0;         // number of items on the queue
 // private int front = -1;           // index of front of queue
 // private int rear = 0;             // index of rear of queue

  // Constructors
  public ArrayQueue1()
  {
    queue = new Object[100];
    capacity = 100;
  }

  public ArrayQueue1(int maxSize)
  {
    queue = new Object[maxSize];
    capacity = maxSize;
  }

  public void enqueue(Object item)
  // Adds an element to the front of this queue
  {

    if(!isFull())
    { queue[numItems] = item;
      numItems = numItems + 1;
    }
  }

  public Object dequeue()
  // Removes an element from the rear of this queue
  {
      Object toReturn = null;
     if(!isEmpty())
     {
         toReturn = queue[0];
     	for(int i = 0; i <= numItems - 2; i++)
     	 queue[i] = queue[i + 1];

     	 queue[numItems - 1] = null;

       numItems = numItems - 1;

     }
      return toReturn;
  }

  public boolean isEmpty()
  // Checks if this queue is empty
  {
    return (numItems == 0);
  }

  public boolean isFull()
  // Checks if this queue is full
  {
    return (numItems == capacity);
  }
}




//public
class ArrayQueue2 implements QueueInterface
{
  private Object[] queue;           // Array that holds queue elements
  private int capacity;             // size of the array (capacity of the queue)
  private int numItems = 0;         // number of items on the queue
  private int front = -1;           // index of front of queue
  private int rear = 0;             // index of rear of queue

  // Constructors
  public ArrayQueue2()
  {
    queue = new Object[100];
    capacity = 100;
  }

  public ArrayQueue2(int maxSize)
  {
    queue = new Object[maxSize];
    capacity = maxSize;
  }

  public void enqueue(Object item)
  // Adds an element to the rear of this queue
   {
      if (!isFull())
      {
        if (numItems == 0)
        {
          front = front + 1;
          queue[rear] = item;
          numItems = numItems + 1;
        }
       else
          {
             if (rear == (capacity - 1))
             {
                rear = 0;
                queue[rear] = item;
                numItems = numItems + 1;
             }
             else
             {
                rear = rear + 1;
                queue[rear] = item;
                numItems = numItems + 1;
             }
           }
        }
    }



  public Object dequeue()
  // Removes an element from the front of this queue
  {


    if (isEmpty())
     return null;

    else

     {

       if (numItems == 1)
       {
       	  Object toReturn = queue[front];
          queue[front] = null;

       	  front = -1;
       	  rear = 0;
       	  numItems = 0;

          return toReturn;

       }
       else
       {
       	  if (front == (capacity - 1))
       	  {
       	  	 Object toReturn = queue[front];
             queue[front] = null;

       	  	 front = 0;
       	     numItems = numItems - 1;

             return toReturn;
       	  }

          else
          {
          	 Object toReturn = queue[front];
             queue[front] = null;

       	  	 front = front + 1;
       	     numItems = numItems - 1;

             return toReturn;
          }

       }

     }
  }

  public boolean isEmpty()
  // Checks if this queue is empty
  {
    return (numItems == 0);
  }

  public boolean isFull()
  // Checks if this queue is full
  {
    return (numItems == capacity);
  }
}

[Wnt2bsleepin]

Please put those in [code][/ code] tags

[DigitalBullets]

Please put those in [code][/ code] tags

sorry I've never used a forum like this before, I edited the post and typed [code] at the beginning and [/ code] at the end but I dont see what it did other than put it there in the post? Im sure I did something wrong

[Wnt2bsleepin]

sorry I've never used a forum like this before, I edited the post and typed [code] at the beginning and [/ code] at the end but I dont see what it did other than put it there in the post? Im sure I did something wrong

You need to remove the space on between the / and Code on the second bracket. I left it in there so it would show.

[DarrylBurke]

http://www.java-forums.org/content/113-forum-rules.html
Guide For New Members

db

[DigitalBullets]

http://www.java-forums.org/content/113-forum-rules.html
Guide For New Members

db

Sorry about the title, and missing the [CODE/CODE] I will make sure not to make that mistake again. Is there a way to delete the thread and re-post it with those fixes? I think it would probably help anything looking at the post answer my questions. Thanks!

[Wnt2bsleepin]

Why is there a Circle object in there?

[code]
class Circle
[/object]

may have some relevance, but it's not related to your question.

Just a question. Is this an assignment for a class. You're dealing with data structures, implemented as an Array and as a Linked List. I have some literature I can post here to show you how to do it.

[DigitalBullets]

Why is there a Circle object in there?

[code]
class Circle
[/object]

may have some relevance, but it's not related to your question.

Just a question. Is this an assignment for a class. You're dealing with data structures, implemented as an Array and as a Linked List. I have some literature I can post here to show you how to do it.

Yes this was an example used in class. The circle class was just a something we went over in class. For the question I only need to write a method, so all that code that was posted isnt really needed as far as I know but it was asked for.

[Wnt2bsleepin]

Well, he gave you the code to put stuff into a Queue and a Stack. Do you know what those are, as well as their implementations as an array or linked list? For future reference, I find it easier to post the individual .class files in their own [code] brackets. Makes it easier to discern between them.