"Learning Notes" C # ArrayList

• Collection
  • A collection is a container in which you use collective management-related groups of objects
  • Collections are divided into non-generic collections and generic collections
• Non-generic collection
  • Using a non-generic collection requires the introduction of a namespace System.Collections
  • arraylist-arrays that can be dynamically added as needed
  • hashtable-hash table used to store key-value pairs
  • Queue-follows the FIFO queue
  • Stack-follows a last-in-first-out stack
• Generic collection
  • Using generic collections requires the introduction of namespaces System.Collections.Generic
  • list<t>-arrays that can be dynamically added as needed
  • Dictionart<tkey, tvalue>-hash table used to store key-value pairs
  • Queue<t>-follows the FIFO queue
  • Stack<t>-follows a last-in-first-out stack
• ArrayList
  • ArrayList is a special array.
  • You can dynamically change the length of an array by adding or removing elements
  • Flexibility to insert, delete, and access elements
  • is not a strong type, slower than a normal array
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  1 usingSystem;2 //using a non-generic collection requires the introduction of namespaces3 usingSystem.Collections;4 5 namespaceArraylistdemo6 {7     class Program8     {9          Public Static voidLog (ArrayList arr)Ten         { One             stringstr ="the current array has"+ arr. Count +"Elements: ("; A              for(inti =0; I < arr. Count; i++) -             { -str + =Arr[i]; the                 if(I < arr.) Count-1) -                 { -str + =","; -                 } +             } -str + =")"; + Console.WriteLine (str); A         } at         Static voidMain (string[] args) -         { -             //1. Create an object first -ArrayList arr =NewArrayList (); - Log (arr); -  in             //add elements using the Add () method, no restrictions on element types -Arr. ADD ( -); toArr. ADD (2.5f); +Arr. ADD ("Li"); - Log (arr); the  *             //use [subscript] to get the element at the specified position $             //Console.WriteLine (arr[0]);Panax Notoginseng  -             //gets the number of elements in the current array the             intCount =arr. Count; +  A             //use the Insert () method to insert an element into a subscript position theArr. Insert (1,"Zhao"); + Log (arr); -  $             //remove a specified element from an array using the Remove () method $Arr. Remove ("Zhao"); - Log (arr); -             //Use the RemoveAt () method to delete the element that specifies the location of the subscript theArr. RemoveAt (0); - Log (arr);Wuyi  the             //Use the bool Contains () method to determine whether the specified element exists in the current array -             BOOLb = arr. Contains ("Li"); Wu  -             //empty the entire array About arr. Clear (); $  -         } -     } -}

"Learning Notes" C # ArrayList