CS535 Object-Oriented Programming & Design
Fall Semester, 1996
Conceptual Definition of OO

1. Conceptual Level Definition

                                Conceptual Definition of OO Slide # 1

• Abstraction

"Extracting the essential details about an item or group of items, while ignoring the unessential details."

Edward Berard

• Encapsulation

Enclosing all parts of an abstraction within a container

• Information Hiding

Hiding parts of the abstraction

• Hierarchy

Abstractions arranged in order of rank or level

                                Conceptual Definition of OO Slide # 2

"A stack is a linear list for which all insertions and deletions are made at one end of the list"

pop, push, isEmpty, isFull

                                Conceptual Definition of OO Slide # 3

class Stack[1]  {
   private float[] elements;
   private int topOfStack = -1;
   
   public Stack( int stackSize )  {
      elements = new float[ stackSize ];
   }
   
   public void push( float item )  {
      elements[ ++topOfStack ] = item;
   }
   
   public float pop()  {
      return elements[ topOfStack-- ];
   }
   
   public boolean isEmpty()  {
      if ( topOfStack < 0 )    return true;
      else               return false;
   }
   
   public boolean isFull()  {
      if ( topOfStack >= elements.length )    return true;
      else                           return false;
   }
}

   Stack me = new Stack( 20 );
   me.push( 5 );
   me.push( 12 );
   System.out.println( me.pop() );
   System.out.println( me.pop() );

                                Conceptual Definition of OO Slide # 4

struct Stack 
{
   float stack[100];      
   int topOfStack;
};

void push(Stack& it, int item) 
{  
   it.stack[(it.topOfStack)++] = item;   
}

float pop(Stack& it)
{  
   return it.stack[--(it.topOfStack)];   
}

main()
{
   Stack TryThisOut;         // TryThisOut, Yours, Mine are 
   Stack Yours, Mine;         //  Stack objects

   TryThisOut.topOfStack = 0;
   Yours.topOfStack = 0;

   push(TryThisOut, 5.0);
   push(Yours, 3.3);
   push(TryThisOut, 9.9);

   cout << pop(TryThisOut) << endl;
}

                                Conceptual Definition of OO Slide # 5

( 3 + 9 - 13 ) * 6 + 2

becomes

3 9 + 13 - 6 * 2 +

read next token

if token is operand push on stack

if token is operator

pop two items off the stack

apply operator to the items from stack

push result on stack

repeat until no more tokens

result is on the top of the stack

                                Conceptual Definition of OO Slide # 6

class CalculatorEngine
{
   private Stack operands = new Stack( 100 );
   
   public float evaluate( String expression )
   {
      StringTokenizer tokenList = new StringTokenizer( expression );
   
      while ( tokenList.hasMoreTokens() )
         processToken( tokenList.nextToken() );
      
      return    operands.pop();
   }
   
   private void processToken( String token )
   {
      if ( token.equals( "+" ) )
         operands.push( operands.pop() + operands.pop() );
         
      else if ( token.equals( "-" ) )
         operands.push( operands.pop() - operands.pop() );
         
      else if ( token.equals( "/" ) )
         operands.push( operands.pop() / operands.pop() );
         
      else if ( token.equals( "*" ) )
         operands.push( operands.pop() * operands.pop() );
      
      else
         operands.push( stringToFloat( token ) );
   }

   private float stringToFloat( String number )
   {
      return Float.valueOf( number ).floatValue();
   }
}

                                Conceptual Definition of OO Slide # 7

class CalculatorGUI
{

   CalculatorEngine rpnEvaluator;

   public CalculatorGUI( CalculatorEngine myComputeEngine )
   {
      rpnEvaluator = myComputeEngine;

      // code to build the gui interface removed
   }

   // code to make gui run removed
}

public static void main( String[] arguments )
{
   CalculatorGUI fourBanger;

   fourBanger = new CalculatorGUI( new CalculatorEngine() );
}

                                Conceptual Definition of OO Slide # 8

                                Conceptual Definition of OO Slide # 9

Identify the data and the operations on the data

These start to form the classes

Determine how classes interact

Create program on top of the classes

                                Conceptual Definition of OO Slide # 10

If class A is-part-of class B then there is no inheritance

An object of type B will interact with an object of type A

Some negotiation between A and B for responsibilities may be needed

Example: