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

2. Defining the class Methods: Constructor: Properties (C#)
public, private or protected
return or not
Properties (C#)
get
set
Constructor:
same name as class
public visibility
default and overloaded
Class instance variables
Should normally be private
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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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4. Overloaded Constructor
public Trophy (string n, int p) {
name = n;
points = p; }
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5. public string Name { get return name; }
Properties (C#)
public int Points {
get
{ return points; }
set
if (value > 0)
points = value; }
public string Name {
get
return name; }
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6. Override of the ToString methodC#
public override string ToString( ) {
return name + " (" + points + ")"; }
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7. Override of the toString method
Java
@Override
public string toString() {
return name + ” (“+points + ”)”; }
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8. 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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9. Array example C# Trophy[] data_storage; int sum = 0;
Console.Write("How many trophies: ");
int trophie_count;
trophie_count = Int32.Parse(Console.ReadLine());
data_storage = new Trophy [trophie_count];
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10. Array example Java Trophy[] data_storage; int sum = 0;
System.out.print("How many trophies: ");
int trophie_count;
trophie_count = scan.nextInt();
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 }
Or use a foreach loop
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 }
Or use a foreach loop
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. 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.
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15. 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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16. Finding the min value using a method
Method FINDMIN ( array nums)
BEGIN
min ← nums[0]
FOR each element in nums
IF nums[I] < min
min = nums[I]
ENDIF
ENDFOR
return min
END FINDMIN
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17. 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;
notice that the parameters (in this case "nums") when you invoke 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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18. Java 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;
notice that the parameters (in this case "nums") when you invoke 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 of elements in nums)
return average
END FINDAVERAGE
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20. Java 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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21. C# 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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