数据结构和算法 – 4.字符串、 String 类和 StringBuilder 类

4.1.String类的应用

class String类应用
    {
        static void Main(string[] args)
        {
            string astring = "Now is The Time";
            //拆分位置
            int pos;
            //单词
            string word;
            ArrayList words = new ArrayList();
            pos = astring.IndexOf(" ");
            while (pos > 0)
            {
                word = astring.Substring(0, pos);
                words.Add(word);
                astring = astring.Substring(pos + 1, astring.Length - (pos + 1));
                pos = astring.IndexOf(" ");
                Console.WriteLine("astring现在的值:" + astring);
            }
            Console.Read();
        }
    }

 

4.1.1.Split 方法和 Join 方法

1.Split 方法取得一条字符串后，就会把它分解成数据成分块，然后把这些块放入 String 数组内。

2.Join 方法从数组变为字符串。

string data = "Mike,McMillan,3000 W. Scenic,North Little Rock,AR,72118";
            string[] sdata;
            char[] delimiter = new char[] { ',' };
            sdata = data.Split(delimiter, data.Length);
            foreach (string tword in sdata)
                Console.WriteLine(tword + " ");


            string joined;
            joined = String.Join(",", sdata);
            Console.Write("
	"+joined);

 

 

4.1.2.比较字符串

1.第一个要检测的比较方法就是 Equal 方法

string s1 = "foobar";
string s2 = "foobar";
if (s1.Equals(s2))
Console.WriteLine("They are the same.");
else
Console.WriteLine("They are not the same.");

 

2.第二个比较字符串的方法就是 CompareTo

string s1 = "foobar";
            string s2 = "foobar";

            int s11 = GetASCII(s1);
            

            Console.WriteLine(s1.CompareTo(s2)); // 相等 returns 0
            s2 = "foofoo";
            Console.WriteLine(s1.CompareTo(s2)); //S2低于S1 returns -1
            s2 = "fooaar";
            Console.WriteLine(s1.CompareTo(s2)); //S2高于S1 returns 1


            int compVal = String.Compare(s1, s2);
            switch (compVal)
            {
                case 0: Console.WriteLine(s1 + " " + s2 + " are equal");
                    break;
                case 1: Console.WriteLine(s1 + " is less than " + s2);
                    break;
                case 2: Console.WriteLine(s1 + " is greater than" + s2);
                    break;
                default: Console.WriteLine("Can't compare");
                    break;
            }

 

3.另外两种在处理字符串时会很有用的比较方法是 StartsWith 和 EndsWith。

string[] nouns = new string[] { "cat", "dog", "bird", "eggs", "bones" };
            ArrayList pluralNouns = new ArrayList();
            foreach (string noun in nouns)
                if (noun.EndsWith("s"))
                    pluralNouns.Add(noun);
            foreach (string noun in pluralNouns)
                Console.Write(noun + " ");

            Console.WriteLine("
");

            string[] words = new string[] { "triangle", "diagonal", "trimester", "bifocal", "triglycerides" };
            ArrayList triWords = new ArrayList();
            foreach (string word in words)
                if (word.StartsWith("tri"))
                    triWords.Add(word);
            foreach (string word in triWords)
                Console.Write(word + " ");

 

 

 

4.1.3.处理字符串的方法

字符串处理通常包括对字符串的改变操作。我们需要在字符串中插入新的字符，从字符串中移除字符，用新字符替换旧字符，改变某些字符的情况，以及向字符串添加空格或者从字符串中移除空格

1.Insert 方法和 Remove 方法

string s1 = "Hello, . Welcome to my class.";
            string name = "TangSanSan";
            int pos = s1.IndexOf(",");
            s1 = s1.Insert(pos + 2, name);
            Console.WriteLine(s1);
            s1 = s1.Remove(pos + 2, name.Length);
            Console.WriteLine(s1);

 

2.Replace 替换

3.PadLeft 方法和 PadRight 方法。 PadLeft 方法会对字符串进行右对齐排列，而 PadRight 方法会对字符串进行左对齐排列。

4.Concat方法。此方法会取走 String对象的列表，把它们串联在一起，然后返回结果字符串。

5.ToLower 方法和 ToUpper 方法还可以把字符串从小写转换成大写形式

6.Trim 方法和 TrimEnd 方法将会把空格或其他字符从字符串的任一端移除掉。

 

 

 

4.2.构造 StringBuilder

在 StringBuilder 类中有几种属性可以用来获取有关 StringBuilder 对象的信息。

Length 属性指定了当前实例中字符的数量，

 Capacity 属性则返回了实例的当前容量。

MaxCapacity 属性会返回对象当前实例中所允许的最大字符数量（尽管这个数量会随着对象添加更多的字符而自动增加）。

1.Append

通过使用 Append 方法可以在 StringBuilder 对象的末尾处添加字符

            StringBuilder stBuff = new StringBuilder();
            String[] words = new string[] {"now ", "is ", "the ", "time ", "for ", "all ",
            "good ", "men ", "to ", "come ", "to ", "the ","aid ", "of ", "their ", "party"};
            for (int i = 0; i <= words.GetUpperBound(0); i++)
                stBuff.Append(words[i]);
            Console.WriteLine(stBuff);

 

2.AppendFormat

给 StringBuilder 对象添加格式字符串,使用AppendFormat

StringBuilder stBuff = new StringBuilder();
            Console.WriteLine();
            stBuff.AppendFormat("Your order is for {0} widgets.", 234);
            stBuff.AppendFormat("
We have {0000} widgets left.", 12);
            Console.WriteLine(stBuff);

 

3.Insert

此方法会取得三个参数。第一个参数说明了插入的开始位置。第二个参数则是要插入的字符串。而作为可选项的第三个参数则是一个整数，它用来说明打算在对象中插入字符串的次数。

StringBuilder stBuff = new StringBuilder();
            Console.WriteLine();
            stBuff.Insert(0, "Hello");
            stBuff.Append("world");
            stBuff.Insert(5, ", ");
            Console.WriteLine(stBuff);
            char[] chars = new char[] { 't', 'h', 'e', 'r', 'e' };
            stBuff.Insert(5, " " + new string(chars));
            Console.WriteLine(stBuff);

 

4.Remove

Remove 方法可以把字符从 StringBuilder 对象中移除掉

 

5.Replace

StringBuilder stBuff = new StringBuilder("HELLO WORLD");
            string st = stBuff.ToString();
            st = st.ToLower();
            st = st.Replace(st.Substring(0, 1),st.Substring(0, 1).ToUpper());
            stBuff.Replace(stBuff.ToString(), st);
            Console.WriteLine(stBuff);