CS211 Spring 2002
Lecture 3: OOP Overview
1/28/2003
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0)  Announcements:
    + Just added? See http://www.cs.cornell.edu/courses/cs211/2003sp/
                  Read syllabus! Do everything in "What To Do First"!!!
    + Office hours and consulting have been happening (1st line of defense!)
    + A1 due Thurs

    Objectives/Topics of Lecture 3
    + Basic ("foundational") data structures
    + Pros and Cons of each
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1)  Variables

     +----+                                Java Syntax
     |    |   <====  1                     - naming rules
     +----+                                - scope
       x                                   - assignment, operators
                                           - default values
     Pros and Cons?




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2) Strings

   + collections of characters
   + objects in Java
   + string literal: "stuff" (saves hassle of calling a constructor)
   + constructors?



   + so, what is a string literal?



   + immutable -- once created, cannot change!



   + Resemblence of Strings to arrays:

   + java.lang.String in API

     Pros and Cons














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3) Arrays

   + fixed collection of objects
    - type[][].... var = new type[size1][size2]....
    - array of arrays in Java

   + indexing


   + initializer lists and anonymous arrays


     Pros and Cons








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4) Lists

   + data structure that can grow
   + limits to size?

   + the gist: field(s) is/are the same (or "related") type as class!
   + think of a field as a LINK

     public class Person {
          public String name;                                style???
          public Person friend;
          public Person(String name) {this.name=name;}
	  public String toString() {return name;}
     }

   + how to build?

     // Create 3 people:       
        Person p1 = new Person("A");
        Person p2 = new Person("B");
        Person p3 = new Person("C");

     // Link people together, with "A" as first person:
















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   + how to operate on list? (perform action(s) on some/all items)

     Count people in our list:

         picture of list: 



         algorithm and pseudocode for iteration: 

             start ___________________

             set _____________________

             if ________________ isn't null

                  ___________ count

                  set _____________________________

             repeat

             output count

         code:
 




   
        

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5) Vectors and ArrayLists

   + Arrays that shrink and grow

   + ArrayList: must import java.util.ArrayList 
     http://java.sun.com/j2se/1.4/docs/api/java/util/ArrayList.html

   + Vector: must import java.util.Vector
     http://java.sun.com/j2se/1.4/docs/api/java/util/Vector.html

     // ArrayList example:
     import java.util.ArrayList;
     public class ArrayList1 {
        public static void main(String[] args) {

           ArrayList vals = new ArrayList(4);

           vals._____(new Person("A"));
	   vals._____(new Person("B"));
	   vals._____(new Person("C"));

	   for (int i=0; i < vals.size() ; i++)
	      System.out.println(vals._____(i));
        }
     }
     // order of printing?


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6) Trees

   + Links to multiple things

   + example:
 
     Build tree of people:

       Person has bio-Mom and bio-Dad

       Start with Person "0" and fill in ancestors

       will get "upside down" tree

       0,1,2,3,4,5,6 becomes:






       called _________ tree


     Java classes?

       class Person {
          public String name;



          public Person(String name) {this.name=name;}
          public String toString() {return name;}
       }

     
     public class Tree1 {
    
        public static void main(String[] args) {

	int height = 3;
	int nodes = (int) ___________________________
	Person[] ps = new Person[nodes];
	
	for (int i = 0; i < nodes-1; i++)
	    ps[i]=new Person("p"+i);
	
	
	ps[ ].mother = ps[ ];
	ps[ ].mother = ps[ ];

	ps[ ].mother = ps[ ];
	ps[ ].mother = ps[ ];

	ps[ ].mother = ps[ ];
	ps[ ].mother = ps[ ];

	// count people....?
	
    }
}

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