What%20If?

1
What If?

• Write a program that prompts for the names and
  locations of 1000 employees. Store the
  information in the program for later use.

2
Program for Previous

• String empName1, empName2, empName3,
• String empLocation1, empLocation2,
• System.out.print( Enter employee name 1)
• empName1 scan.next()
• System.out.print(Enter employee name 2)
• empName2 scan.next()
• //Can we use a loop?

3
Arrays

• Syntax
• type variableName new type size
• Syntax
• type variableName new type size
• Memory Is Set Aside for size Items of type
• Each Variable Location in Array Is Accessed by
  Offsetting into the Array with an Integer
  Expression
• Legitimate Offsets Are 0 to size-1

4
Array Example

• char lastname new char100
• lastname0 H
• lastname1 a
• lastname2 \0
• System.out.println( lastname0)

5
Array Example

• int values new int15
• values0 150
• values1 78
• values2 16
• System.out.println( values0)
• values3 values0 6

6
Array Example

• final int ARRAY_SIZE 100
• int offset
• int numArray new int ARRAY_SIZE
• for(offset 0 offset lt ARRAY_SIZE offset)
• numArrayoffset 0
• for(offset 0 offset lt numArray.length
  offset)
• numArrayoffset offset

7
Array Example
final int ARRAY_SIZE 10 int offset, sum 0,
average int numArray new intARRAY_SIZE f
or(offset 0 offset lt ARRAY_SIZE offset)
System.out.print( Enter Score offset
) numArrayoffset scan.nextInt() for(of
fset 0 offset lt ARRAY_SIZE offset) sum
sum numArrayoffset average sum /
ARRAY_SIZE
8
Arrays of Objects

• // The following does NOT create memory for
• // objects, it only makes a blueprint array
• Employee employees new Employee MAXEMP
• // Must create memory and call constructor for
• // each single member of aray of objects
• for (i 0 i lt MAXEMP i)
• employeesi new Employee()

9
Passing Arrays to Methods

• Pass Array Name into Method
• int intArray new int100
• loadArray(intArray)
• Accept into Method as an Array with No Set Size
• void loadArray( int passedArray )
• Changes to Array in Method will Update Original
  Array

10

• public static void main(String args)
• final int ASIZE 5
• int intArray new intASIZE
• for(int i 0 i lt ASIZE i)
• intArrayi i
• System.out.println( intArray0)
• changeZero(intArray)
• System.out.println( intArray0)
• static void changeZero(int passedArray)
• passedArray0 1000

11
Initializing Arrays

• char cArray3 'a', 'b', 'c'
• int iArray 1, 2, 3, 4
• double dArray 3.4, 5.67e4

12
Two Dimensional Arrays

• char cArray new char1020
• int iArray new int10050
• cArray00 a
• cArray01 b
• cArray919 x
• iArray00 99
• iArray15 135
• iArray9949 0

13
Math Class

• Contains Typical Math Methods
• In Package java.lang (i.e., automatically
  imported)
• Access using Math.math_thing
• Math.PI Math.E (log e 1)
• double pow (double base, double exp)
• double sqrt(double number)
• int round(double number)
• int abs( int number)
• min(number1,number2) and max(number1, number2)
• double random() //random number between 0.0 and
  1.0

14
Tokenizing/Parsing

• Taking Apart a String and Separating It into
  Smaller Strings (i.e., tokens)
• Usually, Tokens are Items Separated by Whitespace
• Tokens Can Be Defined with Different Separators
• Parsing Takes Tokens and Applies Some
  Manipulation of Those Tokens

15
StringTokenizer Class

• import java.util.
• String bigString This is a sentence.
• StringTokenizer st new StringTokenizer(bigString
  )
• while (st.hasMoreTokens())
• System.out.println(st.nextToken())
• // Displays This, is, a, and sentence. one
• // per line

16
Static Variables and Methods

• static means in class methods and variables
• static variable one per class (not one per
  object)
• static method no invoking object (invoke with
  className.method())

17
Static Variable Example

• public class MyClass
• private final int STARTID 1
• private int IDNum -1
• //above are one per object
• private static int nextIDNum STARTID
• //above is one per class
• public MyClass()
• IDNum nextIDNum
• nextIDNum

18
Static Method Example

• public class MyClass
• private final int STARTID 1
• private int IDNum -1
• //above are one per object
• private static int nextIDNum STARTID
• //above is one per class
• public static int GetNextID()
• // Called by MyClass.GetNextID()
• return nextIDNum

19
Other Class Methods

• boolean equals( objType comObj)
• compares invoking object with parameter of same
  type. Returns true if equal, false if not.
• void display()
• displays object to monitor
• String toString()
• converts each attirbute to String and returns
  String

20
Employee Class Review

• Create a Class Employee
• Employee.java
• Employee Attributes (data members)
• Constructor
• Accessor Methods
• Mutator Methods
• toString() and equals()
• tryEmployee.java (Client Test Program)

21
Final Exam

• 2 Hours
• 200 Points
• 35 of Grade
• Must Take to Pass Course

22
Need to Know for Final

• Everything Through Exam 2
• Plus
• Arrays
• Methods
• Classes
• Constructors
• Accessor Methods
• Mutator Methods
• toString() and equals() Methods

23
Final Exam

• 200 Points Total 35 of Final Grade
• 90 points Matching or Short Answer or Multiple
  Choice (Terminology, Operators, JAVA Basics)
• 30 Points Program Output
• 80 Points Programming (Full Programs)