04---Net基础加强
字符串常用方法：
属性： Length获取字符串中字符的个数
IsNullOrEmpty() 静态方法，判断为null或者为“”
ToCharArray() 将string转换为char[]
ToLower() 小写，必须接收返回值（因为字符串的不变性）
ToUpper() 大写
Equals() 比较两个字符串是否相同，忽略大小写的比较，StringComparation
IndexOf() 如果没有找到对应的数据，返回-1
LastIndexOf() 如果没有找到对应的数据，返回-1
Substring() //2个重载，截取字符串
Split() //分割字符串
Join() 静态方法
Format() 静态方法
Repalce()
举例： IsNullOrEmpty() 静态方法，判断为null或者为“”
class Program { static void Main(string[] args) { //string msg = "你好，China"; //string msg = ""; string msg = null;// msg.Length后面会报错 //判断字符串是否为空 //if (msg == "") if (string.IsNullOrEmpty(msg)) { Console.WriteLine("空字符串！！！！"); } else { Console.WriteLine("非空字符串！！！！"); } Console.WriteLine(msg.Length); Console.ReadKey(); } }
字符串的不可变性
class Program { static void Main(string[] args) { //字符串的不可变性指的是字符串一旦声明就不可改变 string s1 = "abc"; s1 = s1 + "d"; Console.WriteLine(s1); //输出abcd Console.ReadKey(); } }
ToUpper() 大写
class Program { static void Main(string[] args) { //string msg = "hEllo"; ////字符串修改完成后必须接收返回值，因为字符串具有不可变性，无法直接修改原来的字符串 //msg=msg.ToUpper(); //Console.WriteLine(msg); //Console.ReadKey(); } }
为什么字符串中的equals方法和==不能判断两个对象是否相同呢？因为字符串中有一个equals方法时判断字符串只要每个字符相同就返回true，并且字符串类型对运算符==进行了重载，也是调用的equals()方法！所以通过equals方法和==不能判断两个对象是否相同！
class Program { static void Main(string[] args) { string s1 = "abc"; string s2 = "abc"; Console.WriteLine(s1.Equals(s2)); //true Console.WriteLine(s1 == s2); //true Console.WriteLine(object.ReferenceEquals(s1, s2)); //true Console.ReadKey(); //此时s1和s2确实为同一个对象， string s1 = "abc"; string s2 = "abc"; 这是因为字符串的“暂存池”（字符串池，字符串拘留池）特性 与下面的 //string s1 = new string(new char[]{'a','b','c'}); //string s2 = new string(new char[] { 'a','b','c' }); //效果不一样，只要出现了new关键字，就表示一定会创建一个新对象 } }
IndexOf() LastIndexOf()
class Program { static void Main(string[] args) { string msg = "我爱你北京天安门，天安门上太阳升。我家不住天安门，天安门上有保安"; int index = msg.IndexOf("天安门"); //5 //int index = msg.LastIndexOf("天安门"); //25 Console.WriteLine(index); Console.ReadKey(); } }
Substring() //截取字符串，2个重载，没有传递截取长度则截取到最后
class Program { static void Main(string[] args) { string msg = "听说过叶长种吗？"; //从坐标为3的索引开始截取，截取长度为3 msg=msg.Substring(3,3); Console.WriteLine(msg); // 结果为叶长种 Console.ReadKey(); } }
Split() //分割字符串
class Program { static void Main(string[] args) { string msg = "乔丹|科比|叶长种"; string[] name=msg.Split('|'); for (int i = 0; i < name.Length; i++) { Console.WriteLine(name[i]); } Console.ReadKey(); } }
class Program { static void Main(string[] args) { string msg = "乔丹|科比|叶长种||||||||詹姆斯"; string[] name=msg.Split(new char[]{'|'},StringSplitOptions.RemoveEmptyEntries); for (int i = 0; i < name.Length; i++) { Console.WriteLine(name[i]); } Console.ReadKey(); } }
class Program { static void Main(string[] args) { string msg = "乔丹|科比|叶长种||||||||詹姆斯"; string[] name=msg.Split(new char[]{'|'},3,StringSplitOptions.RemoveEmptyEntries);//前截取三个 for (int i = 0; i < name.Length; i++) { Console.WriteLine(name[i]); } Console.ReadKey(); } }
Join() 静态方法
class Program { static void Main(string[] args) { string msg = "乔丹|科比|叶长种||||||||詹姆斯"; string[] name=msg.Split(new char[]{'|'},StringSplitOptions.RemoveEmptyEntries); string full = string.Join("=====>",name); Console.WriteLine(full); Console.ReadKey(); } }
Format() 静态方法
class Program { static void Main(string[] args) { //Console.WriteLine("我叫{0}，今年{1}岁了，至今{2}","叶长种",25,"未婚"); //Console.ReadKey(); string msg = string.Format("我叫{0}，今年{1}岁了，至今{2}", "叶长种", 25, "未婚"); Console.WriteLine(msg); Console.ReadKey(); } }
Repalce()
class Program { static void Main(string[] args) { string msg = "大家知道传值与引用的区别吗？请来问叶长重吧"; msg = msg.Replace('重', '种'); Console.WriteLine(msg);//输出：大家知道传值与引用的区别吗？请来问叶长种吧 Console.ReadKey(); } }
class Program { static void Main(string[] args) { string msg = "大家知道传值与引用的区别吗？请来问叶长重吧，哈哈哈哈"; msg = msg.Replace('重', '种').Replace('哈', '嘿'); Console.WriteLine(msg); Console.ReadKey(); } }
字符串练习
输入一个字符串将其字符串以相反的顺序输出如abc输出cba
class Program { static void Main(string[] args) { //接收用户输入的字符串，将其中的字符以与输入相反的顺序输出。 Console.WriteLine("请输入一个字符串："); string msg = Console.ReadLine(); msg = ReverseString(msg); //for (int i = msg.Length-1; i >=0; i--) //{ // Console.Write(msg[i]); //} Console.Write(msg); Console.ReadKey(); } private static string ReverseString(string msg) { Char[] ch = msg.ToCharArray(); for (int i = 0; i < ch.Length/2; i++) { char temp = ch[i]; ch[i] = ch[ch.Length - 1 - i]; ch[ch.Length - 1 - i] = temp; } return new string(ch); }
接收用户输入的一句英文，把里面的单词以相反的顺序输出如 I Love You 输出 uoY evoL I
class Program { static void Main(string[] args) { //接收用户输入的一句英文，将其中的单词以与输入相反的顺序输出。 Console.WriteLine("请输入一句话："); string msg = Console.ReadLine(); string[] words = msg.Split(' '); for (int i = 0; i < words.Length; i++) { words[i] = ReverseString(words[i]); } msg = string.Join(" ", words); Console.Write(msg); Console.ReadKey(); } private static string ReverseString(string msg) { Char[] ch = msg.ToCharArray(); for (int i = 0; i < ch.Length / 2; i++) { char temp = ch[i]; ch[i] = ch[ch.Length - 1 - i]; ch[ch.Length - 1 - i] = temp; } return new string(ch); } }
分割年月日
class Program { static void Main(string[] args) { Console.WriteLine("请输入日期："); string date = Console.ReadLine(); string[] parts = date.Split('年', '月', '日'); Console.WriteLine("年：{0}", parts[0]); Console.WriteLine("月：{0}", parts[1]); Console.WriteLine("日：{0}", parts[2]); Console.ReadKey(); } }
把csv文件中的联系人姓名和电话号码显示出来
class Program { static void Main(string[] args) { string[] lines = File.ReadAllLines("info.csv",Encoding.Default); //循环遍历每一行 for (int i = 0; i < lines.Length; i++) { string[] parts= lines[i].Replace("\"","").Split(','); Console.WriteLine("姓名：{0};电话{1}", parts[0] + parts[1], parts[2]); } Console.ReadKey(); } }
123-456---7---89-----123----2把类似的字符串中重复符号”-”去掉，既得到123-456-7-89-123-2. split()、
class Program { static void Main(string[] args) { string msg = "123-456---7---89-----123----2"; string[] parts = msg.Split(new char[] { '-' }, StringSplitOptions.RemoveEmptyEntries); string str = string.Join("-", parts); Console.WriteLine(str); Console.ReadLine(); } }
从文件路径中提取出文件名(包含后缀) 。比如从c:\a\b.txt中提取出b.txt这个文件名出来。
class Program { static void Main(string[] args) { string path = @"c:\a\b.txt"; // 查找最后一个\出现的索引位置 int index = path.LastIndexOf('\\'); string filename = path.Substring(index + 1); Console.WriteLine(filename); Console.ReadKey(); } }
192.168.10.5[port=21,type=ftp] 192.168.10.5[port=21]
class Program { static void Main(string[] args) { string msg = "192.168.10.5[port=21,type=ftp]"; string[] parts = msg.Split(new string[] { "[port=", ",type=", "]" }, StringSplitOptions.RemoveEmptyEntries); Console.WriteLine("IP:{0}\r\n Port:{1} \r\n service:{2}", parts[0], parts[1], parts.Length == 3 ? parts[2] : "http"); Console.ReadKey(); } }
求员工工资文件中，员工的最高工资、最低工资、平均工资
class Program { static void Main(string[] args) { string[] lines = File.ReadAllLines("salary.txt", Encoding.Default); string[] parts = lines[0].Split('='); //假设第一个人的工资是最高工资 string maxName = parts[0]; int maxSalary = Convert.ToInt32(parts[1]); //假设第一个人的工资是最低工资 string minName = parts[0]; int minSalary = Convert.ToInt32(parts[1]); int sum = minSalary;//用来存储总工资。 int count = 1; //循环遍历其他人的工资进行比对，计算最高工资与最低工资 for (int i = 1; i < lines.Length; i++) { //跳过空行 if (lines[i].Length != 0) { count++; string[] lineParts = lines[i].Split('='); int salary = Convert.ToInt32(lineParts[1]); //进行最高工资的比较 if (salary > maxSalary) { maxSalary = salary; maxName = lineParts[0]; } //进行最低工资的比较 if (salary < minSalary) { minSalary = salary; minName = lineParts[0]; } sum += salary; } } Console.WriteLine("最高工资：{0} 最低工资：{1}", maxSalary, minSalary); Console.WriteLine("平均工资：{0}", sum * 1.0 / count); Console.ReadKey(); } }
“北京传智播客软件培训，传智播客.net培训，传智播客Java培训。传智播客官网：
http://www.itcast.cn。北京传智播客欢迎您。”。在以上字符串中请统计出”传智播客”出现的次数。找IndexOf()的重载。
http://www.itcast.cn。北京传智播客欢迎您。”。在以上字符串中请统计出”传智播客”出现的次数。找IndexOf()的重载。
class Program { static void Main(string[] args) { string msg = "北京传智播客软件培训，传智播客.net培训，传智播客Java培训。传智播客官网：http://www.itcast.cn。北京传智播客欢迎您。"; string defaultWord = "传智播客"; int count = 0; int index = 0; while ((index = msg.IndexOf(defaultWord, index)) != -1) { count++; index = index + defaultWord.Length; } Console.WriteLine("次数是：{0}", count); Console.ReadKey(); } }
面向对象计算器-抽象类版本
抽象计算器类
/// <summary> /// 计算器的一个父类 /// </summary> public abstract class JiSuanQi // 这个类必须定义为抽象类 前面加abstract { public JiSuanQi(int n1, int n2) { this.Number1 = n1; this.Number2 = n2; } public int Number1 { get; set; } public int Number2 { get; set; } public abstract double JiSuan(); }
加法类：
/// <summary> /// 计算加法的类 /// </summary> public class Add : JiSuanQi { public Add(int n1, int n2) : base(n1, n2) { this.Number1 = n1; this.Number2 = n2; } public override double JiSuan() { return this.Number1 + Number2; } }
减法类:
/// <summary> /// 计算减法的类 /// </summary> public class Sub : JiSuanQi { public Sub(int n1, int n2) : base(n1, n2) { this.Number1 = n1; this.Number2 = n2; } public override double JiSuan() { return this.Number1 - Number2; } }
乘法类:
/// <summary> /// 计算乘法的类 /// </summary> public class Mult : JiSuanQi { public Mult(int n1, int n2) : base(n1, n2) { this.Number1 = n1; this.Number2 = n2; } public override double JiSuan() { return this.Number1 * Number2; } }
除法类
/// <summary> /// 计算除法的类 /// </summary> public class Div : JiSuanQi { public Div(int n1, int n2) : base(n1, n2) { this.Number1 = n1; this.Number2 = n2; } public override double JiSuan() { return this.Number1 / Number2; } }
主程序
class Program { static void Main(string[] args) { while (true) { JiSuanQi jsq = null; Console.WriteLine("number1 :"); int n1 = Convert.ToInt32(Console.ReadLine()); Console.WriteLine("操作符"); string czf = Console.ReadLine(); Console.WriteLine("number2 :"); int n2 = Convert.ToInt32(Console.ReadLine()); switch (czf) { case "+": jsq = new Add(n1, n2); break; case "-": jsq = new Sub(n1, n2); break; case "*": jsq = new Mult(n1, n2); break; case "/": jsq = new Div(n1, n2); break; default: break; } if (jsq != null) { double result=jsq.JiSuan(); Console.WriteLine("结果：{0}",result); } } } }
提取方法：
class Program { static void Main(string[] args) { while (true) { JiSuanQi jsq = null; Console.WriteLine("number1 :"); int n1 = Convert.ToInt32(Console.ReadLine()); Console.WriteLine("操作符"); string czf = Console.ReadLine(); Console.WriteLine("number2 :"); int n2 = Convert.ToInt32(Console.ReadLine()); jsq = GetJiSuan(n1, czf, n2); if (jsq != null) { double result=jsq.JiSuan(); Console.WriteLine("结果：{0}",result); } } } //简单工厂设计模式 private static JiSuanQi GetJiSuan(int n1, string czf, int n2) { JiSuanQi jsq=null; switch (czf) { case "+": jsq = new Add(n1, n2); break; case "-": jsq = new Sub(n1, n2); break; case "*": jsq = new Mult(n1, n2); break; case "/": jsq = new Div(n1, n2); break; default: break; } return jsq; } }
值类型与引用类型：
class Program { static void Main(string[] args) { //// 值类型, 栈 ////int short byte char bool double float struct enum decimal ////引用类型 string 数组 类 接口 委托 ////堆 //string s = "a"; //s = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"; ////值类型 //int n = 100; //int m = n; //m = m + 1; //Console.WriteLine(n); // 100 //Console.ReadKey(); //引用类型 Person p = new Person(); p.Age = 100; Person p1 = p; p1.Age = 120; Console.WriteLine(p.Age); //120 Console.ReadKey(); } } public class Person { public int Age { get; set; } }
练习1
class Program { static void Main(string[] args) { //int n = 10; //M1(n); //Console.WriteLine(n);//10 //Console.ReadKey(); //Person p = new Person(); //p.Age = 100; //M2(p); //Console.WriteLine(p.Age);//101 //Console.ReadKey(); //Person p = new Person(); //p.Age = 100; //M3(p); //Console.WriteLine(p.Age);//1000 //Console.ReadKey(); //Person p = new Person(); //p.Age = 100; //M4(p); //Console.WriteLine(p.Age);//100 //Console.ReadKey(); //string name = "科比"; //M5(name); //Console.WriteLine(name);//科比 //Console.ReadKey(); //int[] arrInt = new int[] { 1, 2, 3, 4, 5, 6, 7, 8 }; //M6(arrInt); //for (int i = 0; i < arrInt.Length; i++) //{ // Console.WriteLine(arrInt[i]); // 1, 2, 3, 4, 5, 6, 7, 8 //} //Console.ReadKey(); //int[] arrInt = new int[] { 1, 2, 3, 4, 5, 6, 7, 8 }; //M7(arrInt); //for (int i = 0; i < arrInt.Length; i++) //{ // Console.WriteLine(arrInt[i]); //100,100,100,100,100,100,100,100 //} //Console.ReadKey(); } private static void M7(int[] arrInt) { for (int i = 0; i < arrInt.Length; i++) { arrInt[i] = 100; } } private static void M6(int[] arrInt) { arrInt = new int[arrInt.Length]; for (int i = 0; i < arrInt.Length; i++) { arrInt[i] = arrInt[i] * 2; } } private static void M5(string name1) { name1 = "乔丹"; } private static void M4(Person p1) { p1 = new Person(); p1.Age++; } private static void M3(Person p1) { p1.Age = 1000; p1 = new Person(); p1.Age = 200; } private static void M2(Person p1) { p1.Age++; } private static void M1(int m) { m++; } } public class Person { public int Age { get; set; } }
练习2
class Program { static void Main(string[] args) { //int n = 10; //M1(ref n); //Console.WriteLine(n);//11 //Console.ReadKey(); //Person p = new Person(); //p.Age = 100; //M2(ref p); //Console.WriteLine(p.Age);//101 //Console.ReadKey(); //Person p = new Person(); //p.Age = 100; //M3(ref p); //Console.WriteLine(p.Age);// //Console.ReadKey(); //Person p = new Person(); //p.Age = 100; //M4(ref p); //Console.WriteLine(p.Age);//1 //Console.ReadKey(); //string name = "科比"; //M5(ref name); //Console.WriteLine(name);//乔丹 //Console.ReadKey(); //int[] arrInt = new int[] { 1, 2, 3, 4, 5, 6, 7, 8 }; //M6(ref arrInt); //for (int i = 0; i < arrInt.Length; i++) //{ // Console.WriteLine(arrInt[i]); //0,0,0,0,0,0,0,0 //} //Console.ReadKey(); //int[] arrInt = new int[] { 1, 2, 3, 4, 5, 6, 7, 8 }; //M7(ref arrInt); //for (int i = 0; i < arrInt.Length; i++) //{ // Console.WriteLine(arrInt[i]); //100,100,100,100,100,100,100,100 //} //Console.ReadKey(); } private static void M7(ref int[] arrInt) { for (int i = 0; i < arrInt.Length; i++) { arrInt[i] = 100; } } private static void M6(ref int[] arrInt) { arrInt = new int[arrInt.Length]; for (int i = 0; i < arrInt.Length; i++) { arrInt[i] = arrInt[i] * 2; } } private static void M5(ref string name2) { name2 = "乔丹"; } private static void M4(ref Person p1) { p1 = new Person(); p1.Age++; } private static void M3(ref Person p1) { p1.Age = 1000; p1 = new Person(); p1.Age = 200; } private static void M2(ref Person p1) { p1.Age++; } //值传递，传递的是栈中的内容，（对于值类型，栈中的内容就是对应的数据。对于引用类型栈中内容就是对象的地址） //引用传递，传递的是栈本身的地址，多个变量名实际上指向的是同一个栈变量。 //引用传递必须使用ref关键字修饰。在方法调用的时候传递参数的时候也必须加ref 关键字 private static void M1(ref int m) { m++; } } public class Person { public int Age { get; set; } }