ArrayList表示可以单独索引的对象的有序集合。基本上，它是数组的替代方法。它还允许动态分配内存，添加，搜索和排序列表中的项目。
ArrayList类的属性：
- 可以随时在数组列表集合中添加或删除元素。
- 不能保证对ArrayList进行排序。
- ArrayList的容量是ArrayList可以容纳的元素数。
- 可以使用整数索引访问此集合中的元素。此集合中的索引从零开始。
- 它还允许重复的元素。
- 不支持将多维数组用作ArrayList集合中的元素。
建设者
| Constructor | Description |
|---|---|
| ArrayList() | Initializes a new instance of the ArrayList class that is empty and has the default initial capacity. |
| ArrayList(ICollection) | Initializes a new instance of the ArrayList class that contains elements copied from the specified collection and that has the same initial capacity as the number of elements copied. |
| ArrayList(Int32) | Initializes a new instance of the ArrayList class that is empty and has the specified initial capacity. |
例子：
// C# code to create an ArrayList
using System;
using System.Collections;
using System.Collections.Generic;
class GFG {
// Driver code
public static void Main()
{
// Creating an ArrayList
ArrayList myList = new ArrayList();
// Adding elements to ArrayList
myList.Add("Hello");
myList.Add("World");
Console.WriteLine("Count : " + myList.Count);
Console.WriteLine("Capacity : " + myList.Capacity);
}
}
输出：
Count : 2
Capacity : 4
特性
| Property | Description |
|---|---|
| Capacity | Gets or sets the number of elements that the ArrayList can contain. |
| Count | Gets the number of elements actually contained in the ArrayList. |
| IsFixedSize | Gets a value indicating whether the ArrayList has a fixed size. |
| IsReadOnly | Gets a value indicating whether the ArrayList is read-only. |
| IsSynchronized | Gets a value indicating whether access to the ArrayList is synchronized (thread safe). |
| Item[Int32] | Gets or sets the element at the specified index. |
| SyncRoot | Gets an object that can be used to synchronize access to the ArrayList. |
例子：
// C# program to illustrate the
// ArrayList Class Properties
using System;
using System.Collections;
using System.Collections.Generic;
class GFG {
// Driver code
public static void Main()
{
// Creating an ArrayList
ArrayList myList = new ArrayList();
// Adding elements to ArrayList
myList.Add("A");
myList.Add("B");
myList.Add("C");
myList.Add("D");
myList.Add("E");
myList.Add("F");
// -------- IsFixedSize Property --------
// To check if the ArrayList has fixed size or not
Console.WriteLine(myList.IsFixedSize);
// -------- IsReadOnly Property --------
// To check if the ArrayList is read-only or not
Console.WriteLine(myList.IsReadOnly);
}
}
输出：
False
False
方法
| Method | Description |
|---|---|
| Adapter(IList) | Creates an ArrayList wrapper for a specific IList. |
| Add(Object) | Adds an object to the end of the ArrayList. |
| AddRange(ICollection) | Adds the elements of an ICollection to the end of the ArrayList. |
| BinarySearch(Int32, Int32, Object, IComparer) | Searches a range of elements in the sorted ArrayList for an element using the specified comparer and returns the zero-based index of the element. |
| BinarySearch(Object) | Searches the entire sorted ArrayList for an element using the default comparer and returns the zero-based index of the element. |
| BinarySearch(Object, IComparer) | Searches the entire sorted ArrayList for an element using the specified comparer and returns the zero-based index of the element. |
| Clear() | Removes all elements from the ArrayList. |
| Clone() | Creates a shallow copy of the ArrayList. |
| Contains(Object) | Determines whether an element is in the ArrayList. |
| CopyTo(Array) | Copies the entire ArrayList to a compatible one-dimensional Array, starting at the beginning of the target array. |
| CopyTo(Array, Int32) | Copies the entire ArrayList to a compatible one-dimensional Array, starting at the specified index of the target array. |
| CopyTo(Int32, Array, Int32, Int32) | Copies a range of elements from the ArrayList to a compatible one-dimensional Array, starting at the specified index of the target array. |
| Equals(Object) | Determines whether the specified object is equal to the current object. |
| FixedSize(ArrayList) | Returns an ArrayList wrapper with a fixed size. |
| FixedSize(IList) | Returns an IList wrapper with a fixed size. |
| GetEnumerator() | Returns an enumerator for the entire ArrayList. |
| GetEnumerator(Int32, Int32) | Returns an enumerator for a range of elements in the ArrayList. |
| GetHashCode() | Serves as the default hash function. |
| GetRange(Int32, Int32) | Returns an ArrayList which represents a subset of the elements in the source ArrayList. |
| GetType() | Gets the Type of the current instance. |
| IndexOf(Object) | Searches for the specified Object and returns the zero-based index of the first occurrence within the entire ArrayList. |
| IndexOf(Object, Int32) | Searches for the specified Object and returns the zero-based index of the first occurrence within the range of elements in the ArrayList that extends from the specified index to the last element. |
| IndexOf(Object, Int32, Int32) | Searches for the specified Object and returns the zero-based index of the first occurrence within the range of elements in the ArrayList that starts at the specified index and contains the specified number of elements. |
| Insert(Int32, Object) | Inserts an element into the ArrayList at the specified index. |
| InsertRange(Int32, ICollection) | Inserts the elements of a collection into the ArrayList at the specified index. |
| LastIndexOf(Object) | Searches for the specified Object and returns the zero-based index of the last occurrence within the entire ArrayList. |
| LastIndexOf(Object, Int32) | Searches for the specified Object and returns the zero-based index of the last occurrence within the range of elements in the ArrayList that extends from the first element to the specified index. |
| LastIndexOf(Object, Int32, Int32) | Searches for the specified Object and returns the zero-based index of the last occurrence within the range of elements in the ArrayList that contains the specified number of elements and ends at the specified index. |
| MemberwiseClone() | Creates a shallow copy of the current Object. |
| ReadOnly(ArrayList) | Returns a read-only ArrayList wrapper. |
| ReadOnly(IList) | Returns a read-only IList wrapper. |
| Remove(Object) | Removes the first occurrence of a specific object from the ArrayList. |
| RemoveAt(Int32) | Removes the element at the specified index of the ArrayList. |
| RemoveRange(Int32, Int32) | Removes a range of elements from the ArrayList. |
| Repeat(Object, Int32) | Returns an ArrayList whose elements are copies of the specified value. |
| Reverse() | Reverses the order of the elements in the entire ArrayList. |
| Reverse(Int32, Int32) | Reverses the order of the elements in the specified range. |
| SetRange(Int32, ICollection) | Copies the elements of a collection over a range of elements in the ArrayList. |
| Sort() | Sorts the elements in the entire ArrayList. |
| Sort(IComparer) | Sorts the elements in the entire ArrayList using the specified comparer. |
| Sort(Int32, Int32, IComparer) | Sorts the elements in a range of elements in ArrayList using the specified comparer. |
| Synchronized(ArrayList) | Returns an ArrayList wrapper that is synchronized (thread safe). |
| Synchronized(IList) | Returns an IList wrapper that is synchronized (thread safe). |
| ToArray() | Copies the elements of the ArrayList to a new Object array. |
| ToArray(Type) | Copies the elements of the ArrayList to a new array of the specified element type. |
| ToString() | Returns a string that represents the current object. |
| TrimToSize() | Sets the capacity to the actual number of elements in the ArrayList. |
范例1：
// C# code to check if an element is
// contained in ArrayList or not
using System;
using System.Collections;
using System.Collections.Generic;
class GFG {
// Driver code
public static void Main()
{
// Creating an ArrayList
ArrayList myList = new ArrayList();
// Adding elements to ArrayList
myList.Add("A");
myList.Add("B");
myList.Add("C");
myList.Add("D");
myList.Add("E");
myList.Add("F");
myList.Add("G");
myList.Add("H");
// To check if the ArrayList Contains element "E"
// If yes, then display it's index, else
// display the message
if (myList.Contains("E"))
Console.WriteLine("Yes, exists at index " + myList.IndexOf("E"));
else
Console.WriteLine("No, doesn't exists");
}
}
输出：
Yes, exists at index 4
范例2：
// C# code to remove a range of
// elements from the ArrayList
using System;
using System.Collections;
using System.Collections.Generic;
class GFG {
// Driver code
public static void Main()
{
// Creating an ArrayList
ArrayList myList = new ArrayList(10);
// Adding elements to ArrayList
myList.Add(2);
myList.Add(4);
myList.Add(6);
myList.Add(8);
myList.Add(10);
myList.Add(12);
myList.Add(14);
myList.Add(16);
myList.Add(18);
myList.Add(20);
// Displaying the elements in ArrayList
Console.WriteLine("The initial ArrayList: ");
foreach(int i in myList)
{
Console.WriteLine(i);
}
// removing 4 elements starting from index 0
myList.RemoveRange(0, 4);
// Displaying the modified ArrayList
Console.WriteLine("The ArrayList after Removing elements: ");
// Displaying the elements in ArrayList
foreach(int i in myList)
{
Console.WriteLine(i);
}
}
}
输出：
The initial ArrayList:
2
4
6
8
10
12
14
16
18
20
The ArrayList after Removing elements:
10
12
14
16
18
20
参考：
- https://docs.microsoft.com/zh-cn/dotnet/api/system.collections.arraylist?view=netframework-4.7.2