Tutorial 10     Lecturer: Steve Bellantoni    Tutor: Andria Hunter
===========                      981130 @10am (RW229) @1pm (EM108)

CSC108, Fall 1998                              Tutorial notes, T10
==================================================================

Topics
------

 - A4 questions, explain each method
 - How to implement A4 using arrays


How to Implement A4 Using Arrays
--------------------------------

(1) Simple method where the top of the stack is
      the last element in the array.

   public class LinkedStack {

      private Object[] elements;
      private int elementCount;

      public LinkedStack (int maxSize) {
         elements = new Object [maxSize];
         elementCount = 0;
      }

      public void push (Object data) {
         elements[elementCount] = data;
         elementCount++;
      }
      
      public Object pop () {
         elementCount--;
         return elements[elementCount];
      }
   }

(2) Harder method where the top of the stack is
      the first element (index 0) in the array.

   public class LinkedStack {

      private Object[] elements;
      private int elementCount;

      public LinkedStack (int maxSize) {
         elements = new Object [maxSize];
         elementCount = 0;
      }

      public void push (Object data) {
         // must shift the other elements to the right, to make
         // room for new element which will be inserted at index 0.
         for (int i=elementCount-1; i >= 0; i--) 
            elements[i+1] = elements[i];
         elements[0] = data;
         elementCount++;
      }
      
      public Object pop () {
         // save a reference to object to be returned
         Object tempObject = element[0];

         // must shift the other elements to the left, and
         // return the element at index 0.
         for (int i=1; i < elementCount; i++) 
            elements[i-1] = elements[i];

         elementCount--;
         return tempObject;
      }
   }

Modify A1 to use Arrays
-----------------------

   public class ApplicationCentre {

      private Student[] students;
      private int studentCount;
      private static final int NOTFOUND = -1;

      // Constructor
      public ApplicationCentre (int maxSize) {
         students = new Student [maxSize];
         studentCount = 0;
      }

      // Add new student to application centre
      public boolean addStudent (Student newStudent) {
         if (studentCount < students.length) {
            students[studentCount] = newStudent;
            studentCount++;
            return true;
         }
         return false;
      }
      
      // Find the index of a student in the array
      public int findStudent (String name) {
         for (int i=0; i<studentCount; i++) {
            if (students[i].getName().equals(name))
               return i;
         }
         return NOTFOUND;
      }

      // Remove student from application centre
      // ... if order of the list doesn't matter, we can do
      // it this way....  (Copy element at end of list to
      // index vacated by deleted student)
      public void deleteStudent (String name) {
         int position = findStudent (name);
         if (position != NOTFOUND) {
            students[position] = students[studentCount-1];
            studentCount--;
         }
      }

      // Remove student from application centre
      // ... but if order of the list does matter, we must
      // do it this way....  (shift to left each of the
      // elements from deleted student to end of array.)
      public void deleteStudent (String name) {
         int position = findStudent (name);
         if (position != NOTFOUND) {
            for (int i=position+1; i<studentCount; i++)
               students[i-1] = students[i];
            studentCount--;
         }
      }
   }

Example Using Static Variable & Static Method
---------------------------------------------

   public class Bank_Account {
   
      private double balance;
      private static double bankBalance;
      private String acctNum;
      private String name;
   
      // Constructor - this constructor is used when
      //               starting balance should be 0.
      public Bank_Account (String acctNum, String name) {
         balance = 0.0;
         this.acctNum = acctNum;
         this.name = name;
      }
   
      // Constructor - this constructor is used when starting
      //               balance is passed as the parameter.
      public Bank_Account (double startBalance, String acctNum, String name) {
         balance = startBalance;
         bankBalance += startBalance;
         this.acctNum = acctNum;
         this.name = name;
      }
   
      // Deposit money into the account
      public void deposit (double depositAmount) {
         balance += depositAmount;
         bankBalance += depositAmount;
      }
   
      // Increase the Bank's Balance by amount passed
      public static void depositBank (double depositAmount) {
         bankBalance += depositAmount;
      }
   
      // Increase the Bank's Balance by amount passed
      public String toString () {
         return "Account Holder's Name: " + name + "\n" +
                "Account number: " + acctNum + "\n" +
                "Account balance: " + balance + "\n" +
                "Bank balance: " + bankBalance + "\n";
      }
   }
   
   public class Bank {
   
      public static void main(String args[]) {
   
         // Create 2 bank account objects
         Bank_Account a = new Bank_Account (500.0, "00001", "Sally Green");
         Bank_Account b = new Bank_Account ("00002", "Joe Smith");
   
         // Deposit money into the bank accounts
         a.deposit (500.0);
         b.deposit (100.0);
   
         // Deposit money into the bank
         Bank_Account.depositBank (200.0);
   
         // Report Balances
         System.out.println ("Reporting Summary for Bank Accounts:\n");
         System.out.println (a.toString ());
         System.out.println (b.toString ());
      }
   }

   Output:
Reporting Summary for Bank Accounts:

Account Holder's Name: Sally Green
Account number: 00001
Account balance: 1000.0
Bank balance: 1300.0

Account Holder's Name: Joe Smith
Account number: 00002
Account balance: 100.0
Bank balance: 1300.0