1. Review of Classes and Arrays
Lecture 2
Review of Classes and Arrays
CSE 1322
4/26/2018

2. Defining the class Constructor: Class instance variables Methods:
same name as class
public visibility
default and overloaded
Class instance variables
Should normally be private
Methods:
public, private or protected
return or not
Properties (C#)
get
set
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3. Class definition and default constructor
public class Trophy{ private string name; private int points = 10; public Trophy(){ name = "Yeah that's a problem"; points = 0; } public Trophy (string n, int p){ name = n; points = p; }
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Note: Java is String, C# is string

4. The Overloaded Constructor
public Trophy (string n, int p) {
name = n;
points = p; }
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5. Properties (C#)
public string Name {
get {
return name; }
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6. Properties (C#) public int Points { get { return points; } set
if (value > 0)
points = value; }
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7. Override of the ToString method
public override string ToString( ) { return name + " (" + points + ")"; }
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8. Override of the toString method
@Override public string toString() { return name + ” (“+points + ”)”; }
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9. Arrays Trophy[ ] troph; troph = new Trophy[10]; or
Trophy [] troph = new Trophy[10];
can't use until memory is allocated with new.
In C#, the [] must be between the data type and the object reference while in java the [] can be between the or after the name.
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10. Array example
Trophy[] data_storage; int sum = 0; PRINT("How many trophies: "); int trophie_count; trophie_count = READ(); data_storage = new Trophy [trophie_count];
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11. Traversing an array
Use a for, while or do-while starting at index 0 and going to the last element FOR each element in the array do something ENDFOR
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12. Traversing an array - C#
Use a for, while or do-while starting at index 0 and going thru .Length-1
for (int i=0; i< data_storage.Length; i++)
{ do something }
foreach(Trophy t in data_storage)
{ do something as long as it doesn't add or remove members of the array }
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13. Traversing an array – Java
Use a for, while or do-while starting at index 0 and going thru .length-1
for (int i=0; i< data_storage.length; i++)
{ do something }
for (Trophy t : data_storage)
{ do something as long as it doesn't add or remove members of the array }
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14. Note about Capitalization
Java uses .length
C# uses .Length
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15. Array processing
The simplest processes involve searching ( finding a value, finding the largest or smallest ),or finding a sum, product or average.
Remember to initialize properly.
Note the pattern in the next examples: we use a loop!
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16. Array processing 2
int[] nums = new int[10]; … float average = FindAverage(nums); int min = FindMin(nums); remember to use "new" to allocate memory for your object.
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17. Finding the min value using a methodPs
Method FINDMIN ( array nums) BEGIN min ← nums[0] FOR each element in nums IF element < min min = element ENDIF ENDFOR return min END FINDMIN
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18. C# finding the min
private static int FindMin (int[] A) {
int temp = A[0];
for (int i = 1; i < A.Length ); i++) {
if (temp > A[i])
temp = A[i]; }
return temp;
Note the parameters (in this case "nums") when you call a method can be called something else in the method itself (in this case "A").  Parameters match in position and type, so the name doesn't matter.
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19. Finding the sum or average using a method
Method FINDAVERAGE (array nums)
BEGIN
sum ← 0
FOR each element in nums
sum = sum + nums[I]
ENDFOR
average = (sum*1.0)/(number elements in nums)
return average
END FINDAVERAGE
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20. Finding a sum and/or average
private static float FindAverage (int[] B) { int sum = 0; for (int i = 0; i < B.length; i++) sum += B[i]; } return (float)sum / B.length;
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