C＃|创建具有指定容量的StringBuilder

StringBuilder(Int32)构造函数用于初始化StringBuilder类的新实例，该实例将为空并具有指定的初始容量。 StringBuilder的用于表示字符的可变的字符串。可变是指可以更改的字符串。所以String对象是不可变的，但StringBuilder是可变的字符串类型。它不会创建当前字符串对象的新修改实例，但会在现有字符串对象中进行修改。

句法：

public StringBuilder (int capacity);

在这里，容量是StringBuilder实例的起始大小。如果要存储的字符数大于指定的容量，则StringBuilder对象将动态分配内存以存储它们。

异常：如果容量小于零，则将提供ArgumentOutOfRangeException。

范例1：

// C# Program to illustrate how
// to create a StringBuilder having
// specified initial capacity
using System;
using System.Text;
using System.Collections;
  
class Geeks {
  
    // Main Method
    public static void Main(String[] args)
    {
  
        // sb is the StringBuilder object
        // StringBuilder(10) is the constructor
        // used to initializes a new
        // instance of the StringBuilder class
        // having 10 as capacity
        StringBuilder sb = new StringBuilder(10);
  
        Console.Write("Capacity of StringBuilder: ");
  
        // using capacity property
        Console.WriteLine(sb.Capacity);
    }
}

输出：

Capacity of StringBuilder: 10

示例2：对于ArgumentOutOfRangeException

// C# Program to illustrate how
// to create a StringBuilder having
// specified initial capacity
using System;
using System.Text;
using System.Collections;
  
class Geeks {
  
    // Main Method
    public static void Main(String[] args)
    {
  
        // sb is the StringBuilder object
        // taking capacity less than zero
        StringBuilder sb = new StringBuilder(-4);
  
        // using capacity property
        Console.WriteLine(sb.Capacity);
    }
}

运行时错误：

Unhandled Exception:
System.ArgumentOutOfRangeException: ‘capacity’ must be greater than zero.
Parameter name: capacity

参考：

• https://docs.microsoft.com/zh-cn/dotnet/api/system.text.stringbuilder.-ctor?view=netframework-4.7.2#System_Text_StringBuilder__ctor_System_Int32_