Collections and Generic Collections

Collection:
As a case, there is no fixed length, you can put any type of data or variables;
The collection also has an index;

ArrayList:
Defined:
ArrayList arr = new ArrayList ();
To add an element:
Arr. Add (a);
Arr. ADD (b);

Value:
arr[index];
Note that the value is an object type and requires a type conversion;

Note: A collection can be any type, but when we use a set, we usually put a type;

Special Features:
Arr. ADD (); adding elements
Arr. Insert (index, value); Jump in queue, jump the value into the index position
Arr. Remove (value); Remove elements from a collection based on values
Arr. RemoveAt (index); To delete an element in a collection based on an index
Arr. Clear (); Emptying the collection

Arr. Sort (); Arranges all elements in a collection from small to large
Arr. Reverse ();
Arr. Contains (); To see if an element is contained in the collection
Arr.count; The number of elements in the collection, returning an int type

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Exercises:
Please enter the number of students:
Please enter the name of the 1th student:
Please enter the 1th student's gender:
Please enter a 1th student's age:
Please enter the 1th student's grade:
...
N
********************************
1th Student's name: XXX, Gender: xxx, Age: XXX, score: XXX.
...
N

Practice Questions: Please enter the number of students: Please enter the 1th student's name: Please enter the 1th student's gender: Please enter the age of the 1th student: Please enter the 1th student's grade: ... n********************************1th Student's name: XXX, Gender: xxx, Age: XXX, score: XXX. ... n Console.Write ("Please enter the number of students:"); intGS =Convert.ToInt32 (Console.ReadLine ()); ArrayList a=NewArrayList (); ArrayList b=NewArrayList (); ArrayList C=NewArrayList (); ArrayList D=NewArrayList (); decimalEnd =0m;  for(inti =0; I < GS; i++) {Console.Write ("Please enter section"+ (i +1) +"name of student:"); stringXM =Console.ReadLine (); Console.Write ("Please enter section"+ (i +1) +"Gender of Student:"); stringXB =Console.ReadLine (); Console.Write ("Please enter section"+ (i +1) +"age of Student:"); intNL =Convert.ToInt32 (Console.ReadLine ()); Console.Write ("Please enter section"+ (i +1) +"Student Results:"); decimalCJ =Convert.todecimal (Console.ReadLine ());                A.add (XM);                B.add (XB);                C.add (NL);                D.add (CJ); End+=CJ; } Console.WriteLine ("**************************************************");  for(intj =0; J < GS; J + +) {Console.WriteLine ("Section"+ (J +1) +"the name of a student:"+ A[j] +", Gender:"+ B[j] +", Age:"+ C[j] +", Results:"+ D[j] +". "); } Console.WriteLine ("The total score is:"+ END +"The average score is:"+ (END/GS) +". "); Console.readkey ();

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Special Collections:

Queue Queues Collection
Defined:
Queue QQ = new Queue ();
To add an element:
Enqueue ("value"/variable);
Value:
Dequeue (); Takes the first entry value and removes it from the collection.
Peek (); Take the first entry value to show you that it will not be deleted in the collection
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Stack Trestle Collection
Defined:
Stack ss = new stack ();
To add an element:
Ss. Push ("value"/variable);
Value:
Ss. Pop (); Advanced go out, take the last one in, and delete in the collection
Ss. Peek (); Take the last one in, show it to you, and not remove it from the collection.
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Hashtable: Hashtable Collection
Key-value pairs, one for the corresponding value;
Defined:
Hashtable ha = new Hashtable ();
To add an element:
ADD (Key,value); Key, user-defined index, object type
Value that corresponds to the current index
Value:
Ha[key]; Remove the corresponding content according to user-defined index

Traverse:
foreach (String i in Ha. Keys)//You can traverse the keys individually
{
Console.WriteLine (i);
}

foreach (String i in Ha. Values)//The value can be traversed independently
{
Console.WriteLine (i);
}
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Generic collection:
list< type > li = new list< type > ();

Li. ADD (a value or variable of the same type);

li[Index]

Collections and Generic Collections