自己写的精简版StringBuilder类附源码

* 由于字符串的相加会产生了一个新的字符串，当有多个字符串相加时，就会不断的有字符串构造出来和被析构掉，当然这是相当耗资源的。
* 所以就有了StringBuilder类。
* StringBuilder的实现方式是这样的，默认分配16个字节的空间，如果追加的字符个数超过当前分配的空间，
* 系统就重新分配一块两倍的空间，16,,32,64,128,256....。再把字符串的值拷贝到新的内存中。以前的内存等着垃圾回收器回收。
* 这样也会有大量的内存被分配和回收。
* 但StringBuilder可没有那么笨，它可以分配指定大小的连续内存用于存储字符串，如果指定的内存大小刚好容纳所有的字符串，
* 那就不会有多余的内存分配和回收，所以在使用StringBuilder的时候，如果能估计将要存放的字符个数的话，分配恰当的内存，
* 将会大大的提高程序的性能，可惜的是(个人认为)很多程序员在使用StringBuilder的时候都没有预分配内存。
* 它用一个字符数组存放字符串，每次追加字符串的时候，都是往数组的后面追加字符串，
* 所以操作字符串中指定的字符非常方便，读取所有字符串也很快。
* 以下是我自己写的精简版的StringBuilder类。
* 个人认为微软实现的方式跟我的差不多，由于本人技术有限（只是比较喜欢技术），没有遇到技术非常牛逼的人，也没有看过非常牛逼的代码，
* 开源的代码看得好累，有点不知所云，所以我暂时还很难写出较好的代码，以下代码肯定漏洞百出，
* 以下代码我自己还是用了点时间写的，对于程序的初学者来说应该有点帮助，
* 希望程序大牛千万不要手软，多加批评，多加指导，我定虚心认真学习源码下载

源码

1 using System;
2 
3  namespace CthSoft
4 {
5     public class StringBuilder
6     {

属性

 1 #region 属性
 2         char[] strBuf;//存储字符串的字符数组
 3  
 4         private int capacity=16;//字符数组的容量
 5          public int Capacity
 6         {
 7             get { return capacity; }
 8             set
 9             {
10                 SetCapacity(value);
11                 this.capacity = value;
12             }
13         }
14 
15         private int length;//字符串的长度
16          public int Length
17         {
18             get { return length; }
19             set
20             {
21                 //字符串长度不能小于0
22                 if (value < 0)
23                 {
24                     throw new ArgumentOutOfRangeException("长度不能小于 0。参数名: length");
25                 }
26 
27                 if (value == capacity)
28                 {
29                     return;
30                 }
31 
32                 if (value > capacity)
33                 {
34                     this.Capacity = value;
35                 }
36                 else
37                 {
38                     for (int i = value; i < length; i++)
39                     {
40                         strBuf[i] = '\0';
41                     }
42                 }
43 
44                 this.length = value;
45             }
46         }
47 
48         //字符数组的最大容量，即int类型的最大值(容量是int类型)
49         private int maxCapacity = int.MaxValue;
50         public int MaxCapacity
51         {
52             set { maxCapacity = value; }
53             get { return maxCapacity; }
54         }
55         #endregion

辅助方法

 1  #region 辅助方法
 2         private void SetCapacity(int value)
 3         {
 4             CheckCapacitySize(value,this.maxCapacity);
 5             if (strBuf != null)
 6             {
 7                 char[] tmpBuf = new char[value];
 8                 Array.Copy(strBuf, tmpBuf, strBuf.Length);
 9                 strBuf = tmpBuf;
10                 tmpBuf = null;
11             }
12             else {
13                 strBuf = new char[value];
14             }
15         }
16 
17         private void SetCapacity()
18         {
19             if (this.length > this.capacity)
20             {
21                 while (this.length > this.capacity)
22                 {
23                     this.capacity = this.capacity << 1;
24                 }
25                 SetCapacity(this.capacity);
26             }
27         }
28 
29         private void CheckCapacitySize(int capacity, int maxCapacity)
30         {
31             CheckRange(capacity);
32             CheckRange(maxCapacity);
33             if (maxCapacity < capacity)
34             {
35                 throw new ArgumentOutOfRangeException("容量超出了最大容量。参数名: capacity");
36             }
37         }
38 
39         private void CheckRange(int index)
40         {
41             if (index < 0)
42             {
43                 throw new IndexOutOfRangeException("索引超出了数组界限。参数名: index");
44             }
45         }
46 
47         private void CheckRange(int index, int count)
48         {
49             CheckRange(index);
50             CheckRange(count);
51             CheckRange(index + count);
52         }
53         #endregion

初始化

 1  #region 初始化
 2         private void Initializtion(int length)
 3         {
 4             strBuf = new char[this.capacity];
 5             this.length = length;
 6         }
 7          
 8         private void Initializtion(ref string value)
 9         {
10             if (value == null)
11             {
12                 Initializtion(0);
13             }
14             else
15             {
16                 while (value.Length > this.capacity)
17                 {
18                     this.capacity = this.capacity << 1;
19                 }
20                 Initializtion(value.Length);
21                 Array.Copy(value.ToCharArray(), strBuf, value.Length);
22             }
23         }
24 
25         private void Initializtion(ref string value,int capacity)
26         {
27             CheckRange(capacity);
28             this.capacity = capacity;
29             Initializtion(ref value);
30         }
31         #endregion

构造函数

 1  #region 构造函数
 2         public StringBuilder()
 3         {
 4             Initializtion(0);
 5         }
 6 
 7         public StringBuilder(string value)
 8         {
 9             Initializtion(ref value);
10         }
11 
12         public StringBuilder(string value, int capacity)
13         {
14             Initializtion(ref value,capacity);
15         }
16 
17         public StringBuilder(int capacity)
18         {
19             string value = null;
20             Initializtion(ref value, capacity);
21         }
22 
23         public StringBuilder(int capacity, int maxCapacity)
24         {
25             CheckCapacitySize(capacity,maxCapacity);
26             this.capacity = capacity;
27             this.maxCapacity = maxCapacity;
28             Initializtion(0);
29         }
30 
31         public StringBuilder(string value, int startIndex, int length, int capacity) 
32         {
33             if (startIndex < 0 || length < 0 || startIndex >= value.Length || startIndex + length >= value.Length)
34             {
35                 throw new ArgumentOutOfRangeException("索引和长度必须引用该字符串内的位置");
36             }
37             value = value.Substring(startIndex, length);
38             Initializtion(ref value, capacity);
39         }
40         #endregion

Append

  1  #region Append
  2         public StringBuilder Append(char[] value)
  3         {
  4             return Append(value,0,value.Length);
  5         }
  6 
  7         public StringBuilder Append(string value)
  8         {
  9             if (value == null)
 10             {
 11                 value = string.Empty;
 12             }
 13             Append(value.ToCharArray());
 14             return this;
 15         }
 16 
 17         public StringBuilder Append(object value)
 18         {
 19             if (value == null)
 20             {
 21                 value = string.Empty;
 22             }
 23             Append(value.ToString().ToCharArray());
 24             return this;
 25         }
 26 
 27         public StringBuilder Append(int value)
 28         {
 29             Append(value.ToString().ToCharArray());
 30             return this;
 31         }
 32 
 33         public StringBuilder Append(byte value)
 34         {
 35             Append(value.ToString().ToCharArray());
 36             return this;
 37         }
 38 
 39         public StringBuilder Append(long value)
 40         {
 41             Append(value.ToString().ToCharArray());
 42             return this;
 43         }
 44 
 45         public StringBuilder Append(float value)
 46         {
 47             Append(value.ToString().ToCharArray());
 48             return this;
 49         }
 50 
 51         public StringBuilder Append(double value)
 52         {
 53             Append(value.ToString().ToCharArray());
 54             return this;
 55         }
 56 
 57         public StringBuilder Append(decimal value)
 58         {
 59             Append(value.ToString().ToCharArray());
 60             return this;
 61         }
 62 
 63         public StringBuilder Append(bool value)
 64         {
 65             if (value)
 66             {
 67                 Append("True".ToCharArray());
 68             }
 69             else {
 70                 Append("False".ToCharArray());
 71             }
 72             return this;
 73         }
 74 
 75         public StringBuilder Append(char value, int repeatCount)
 76         {
 77             if (repeatCount < 0)
 78             {
 79                 throw new ArgumentOutOfRangeException("字符的数量必须大于零，参数repeatCount");
 80             }
 81             char[] tmpBuf = new char[repeatCount];
 82             for (int i = 0; i < repeatCount; i++)
 83             {
 84                 tmpBuf[i] = value;
 85             }
 86             return Append(tmpBuf);
 87         }
 88 
 89         public StringBuilder Append(char[] value, int startIndex, int charCount)
 90         {
 91             if (value == null)
 92             {
 93                 value = new char[] { '\0' };
 94             }
 95             if (startIndex < 0 || charCount < 0 || startIndex + charCount > value.Length)
 96             {
 97                 throw new IndexOutOfRangeException("索引超出了数组界限。参数名: index");
 98             }
 99             this.length = this.length + charCount;
100             SetCapacity();
101             Array.Copy(value, startIndex, strBuf, this.length - value.Length, charCount);
102             return this;
103         }
104 
105 
106         public StringBuilder AppendFormat(string format, object arg0) 
107         {
108             return Append(string.Format(format, arg0));
109         }
110 
111         public StringBuilder AppendFormat(string format, params object[] args)
112         {
113             return Append(string.Format(format, args));
114         }
115 
116         public StringBuilder AppendFormat(string format, object arg0, object arg1)
117         {
118             return Append(string.Format(format, arg0,arg1));
119         }
120 
121         public StringBuilder AppendFormat(string format, object arg0, object arg1, object arg2)
122         {
123             return Append(string.Format(format, arg0, arg1,arg2));
124         }
125         #endregion

Insert

  1 #region Insert
  2         public StringBuilder Insert(int index, char[] value)
  3         {
  4             if (value == null)
  5             {
  6                 return this;
  7             }
  8             if (index < 0 || index > this.length)
  9             {
 10                 throw new IndexOutOfRangeException("索引超出了数组界限。参数名: index");
 11             }
 12 
 13             this.length = this.length + value.Length;
 14             if (this.length > this.capacity)
 15             {
 16                 SetCapacity(this.length);
 17             }
 18              
 19             for (int i = this.length-1-value.Length; i >=index ; i--)
 20             {
 21                 strBuf[i + value.Length] = strBuf[i];
 22             }
 23             for (int i = 0; i < value.Length; i++)
 24             {
 25                 strBuf[index + i] = value[i];
 26             }
 27              
 28             return this;
 29         }
 30 
 31         public StringBuilder Insert(int index, string value)
 32         {
 33             if (value == null)
 34             {
 35                 return this;
 36             }
 37             return Insert(index,value.ToCharArray());
 38         }
 39 
 40         public StringBuilder Insert(int index, byte value)
 41         {
 42             return Insert(index, value.ToString().ToCharArray());
 43         }
 44 
 45         public StringBuilder Insert(int index, char value)
 46         {
 47             CheckRange(index);
 48             this.length++;
 49             if (this.length > this.capacity)
 50             {
 51                 SetCapacity(this.length);
 52             }
 53 
 54             for (int i = this.length - 2; i >= index; i--)
 55             {
 56                 strBuf[i + 1] = strBuf[i];
 57             }
 58             strBuf[index] = value;
 59             return this;
 60         }
 61 
 62         public StringBuilder Insert(int index, int value)
 63         {
 64             return Insert(index, value.ToString().ToCharArray());
 65         }
 66 
 67         public StringBuilder Insert(int index, long value)
 68         {
 69             return Insert(index, value.ToString().ToCharArray());
 70         }
 71 
 72         public StringBuilder Insert(int index, double value)
 73         {
 74             return Insert(index, value.ToString().ToCharArray());
 75         }
 76 
 77         public StringBuilder Insert(int index, object value)
 78         {
 79             return Insert(index, value.ToString().ToCharArray());
 80         }
 81 
 82         public StringBuilder Insert(int index, short value)
 83         {
 84             return Insert(index, value.ToString().ToCharArray());
 85         }
 86 
 87         public StringBuilder Insert(int index, decimal value)
 88         {
 89             return Insert(index, value.ToString().ToCharArray());
 90         }
 91 
 92         public StringBuilder Insert(int index, float value)
 93         {
 94             return Insert(index, value.ToString().ToCharArray());
 95         }
 96 
 97         public StringBuilder Insert(int index, string value, int count)
 98         {
 99             if (value == null)
100             {
101                 return this;
102             }
103             CheckRange(index);
104             if (count < 0)
105             {
106                 throw new ArgumentOutOfRangeException("index 小于零或大于此实例的当前长度。- 或 - count 小于零");
107             }
108             if (value.Length * count+this.length > this.maxCapacity)
109             {
110                 throw new OutOfMemoryException("对象的当前长度加上 value 的长度乘以 count 的值超过StringBuilder.MaxCapacity。");
111             }
112             char[] tmpBuf = new char[value.Length * count];
113             for (int i = 0; i < count; i++)
114             {
115                 Array.Copy(value.ToCharArray(),0,tmpBuf, value.Length*i,value.Length);
116             }
117             Insert(index,tmpBuf);
118             tmpBuf = null;
119             return this;
120         }
121 
122         public StringBuilder Insert(int index, char[] value, int startIndex, int charCount)
123         {
124             if (value == null || value.Length == 0)
125             {
126                 return this;
127             }
128 
129             if (index<0 || charCount<0 ||startIndex + charCount>value.Length)
130             {
131                 throw new IndexOutOfRangeException("索引超出了数组界限。参数名: charCount");
132             }
133 
134             char[] tmpBuf = new char[charCount];
135             Array.Copy(value,startIndex,tmpBuf,0,charCount);
136             Insert(index, tmpBuf);
137             tmpBuf = null;
138             return this;
139         }
140 
141 
142 
143         #endregion

Remove

 1  #region remove
 2         public StringBuilder Remove(int startIndex, int length)
 3         {
 4             CheckRange(startIndex , length);
 5 
 6             for (int i = startIndex + length; i < this.length; i++)
 7             {
 8                 strBuf[startIndex++] = strBuf[i];
 9             }
10             for (int i = startIndex; i < this.length; i++)
11             {
12                 strBuf[i] = '\0';
13             }
14             this.length = this.length - length;
15             return this;
16         }
17 
18         public StringBuilder Remove(char[] value)
19         {
20             if (value == null || value.Length > this.length)
21             {
22                 return this;
23             }
24             int k,t;
25             for (int i = 0; i < this.length; i++)
26             {
27                 if (value[0] == strBuf[i])
28                 {
29                     k = i;
30                     t=0;
31                     while (k < this.length && t < value.Length)
32                     {
33                         if (value[t++] != strBuf[k++])
34                         {
35                             break;
36                         }
37 
38                         if (t == value.Length)
39                         {
40                            return Remove(i, t);
41                         }
42                     }
43                 }
44             }
45             return this;
46         }
47 
48         public StringBuilder Remove(string value)
49         {
50             if (value == null)
51             {
52                 return this;
53             }
54             return Remove(value.ToCharArray());
55         }
56          
57         public StringBuilder RemoveAll(string value)
58         {
59             if (value == null || value.Length > this.length)
60             {
61                 return this;
62             }
63             int k, t;
64             for (int i = 0; i < this.length; i++)
65             {
66                 if (value[0] == strBuf[i])
67                 {
68                     k = i;
69                     t = 0;
70                     while (k < this.length && t < value.Length)
71                     {
72                         if (value[t++] != strBuf[k++])
73                         {
74                             break;
75                         }
76 
77                         if (t == value.Length)
78                         {
79                             Remove(i, t);
80                             break;
81                         }
82                     }
83                 }
84             }
85             return this;
86         }
87         #endregion

Replace

 1  #region replace
 2         public StringBuilder Replace(char oldChar, char newChar)
 3         {
 4             for (int i = 0; i < strBuf.Length;i++ )
 5             {
 6                 if (strBuf[i] == oldChar)
 7                 {
 8                     strBuf[i] = newChar;
 9                 }
10             }
11             return this;
12         }
13 
14         public StringBuilder Replace(char oldChar, char newChar, int startIndex, int count)
15         {
16             CheckRange(startIndex , length);
17 
18             for (int i = startIndex; i < startIndex + count; i++)
19             {
20                 if (strBuf[i] == oldChar)
21                 {
22                     strBuf[i] = newChar;
23                 }
24             }
25             return this;
26         }
27 
28         public StringBuilder Replace(string oldValue, string newValue)
29         {
30             return Replace(oldValue,newValue,0,this.length);
31         }
32 
33         public StringBuilder Replace(string oldValue, string newValue, int startIndex, int count)
34         {
35             CheckRange(startIndex , count);
36             if (oldValue == null || oldValue.Length > this.length)
37             {
38                 return this;
39             }
40 
41             if (newValue == null)
42             {
43                 newValue = string.Empty;
44             }
45 
46             int i, k;
47             bool isChange = false;
48             for (int j = startIndex; j < startIndex+count; j++)
49             {
50                 if (oldValue[0] == strBuf[j])
51                 {
52                     k = j;
53                     i = 0;
54                     while (i <= oldValue.Length && k <= this.length)
55                     {
56                         if (oldValue[i++] != strBuf[k++])
57                         {
58                             break;
59                         }
60                         if (i == oldValue.Length)
61                         {
62                             i = 0;
63                             k = j;
64                             while (i < oldValue.Length && i < newValue.Length)
65                             {
66                                 strBuf[k++] = newValue[i++];
67                             }
68 
69                             if (newValue.Length > i)
70                             {
71                                 Insert(i, newValue.Substring(i));
72                             }
73                             else if (oldValue.Length > i)
74                             {
75                                 Remove(k, oldValue.Length - i);
76                             }
77                             isChange = true;
78                             break;
79                         }
80                     }
81                     if (isChange)
82                     {
83                         j = j + Math.Min(oldValue.Length , newValue.Length)-1;
84                         isChange = false;
85                     }
86                 }
87             }
88             return this;
89         }
90 
91         #endregion

ToString

 1    public char this[int index]
 2         {
 3             set
 4             {
 5                 CheckRange(index);
 6                 strBuf[index] = value;
 7             }
 8             get
 9             {
10                 CheckRange(index);
11                 return strBuf[index];
12             }
13         }
14          
15         public override string ToString()
16         {
17             return new string(strBuf);
18         }
19          
20         public string ToString(int startIndex, int length)
21         {
22             CheckRange(startIndex,length);
23             char[] tmpBuf = new char[length];
24             Array.Copy(strBuf,startIndex,tmpBuf,0,length);
25             return new string(tmpBuf);
26         }
27          
28     }
29 }

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原文地址：https://www.cnblogs.com/hlxs/p/StringBuilder.html

自己写的精简版StringBuilder类 附源码

自己写的精简版StringBuilder类附源码