C#动态数组ArrayList介绍

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ArrayList是一种动态数组，其容量可随着我们的需要自动进行扩充.

ArrayList位于System.Collections命名空间中，所以我们在使用时，需要导入此命名空间.

下面，我们还是在Student类的基础上利用ArrayList操作，从而了解ArrayList的用法

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public class Student  
{  
              public Student(){}  
   
              public Student(String name,int age,String hobby)   
              {  
                           this.Name = name;   
                           this.Age = age;   
                           this.Hobby = hobby;   
              }  
   
              private String name;   
              public String Name   
             {  
                     get{return name;}  
                     set{name = value;}   
             }  
   
             private int age;  
             public int Age  
            {  
                     get{return age;}  
                     set{age = value;}   
            }  
   
            private String hobby;   
            public String Hobby   
           {  
                     get{return hobby;}  
                     set{hobby = value;}   
           }  
   
            public void say()  
            {  
                     Console.WriteLine("大家好，我是'{0}'，今年{1}岁，我喜欢'{2}'",  
                      this.Name,this.Age,this.Hobby);  
            }  
} 

编写测试类，了解ArrayList的方法

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using System.Collections;  
   
public class TestStudent  
{  
              public static void main(String args [])   
             {  
                         //建立ArrayList对象  
           ArrayList students = new ArrayList();  
   
                         //实例化几个Student类对象  
           Student rose = new Student("rose",25,"reading");  
                          Student jack = new Student("jack",28,"singing");  
                          Student mimi = new Student("mimi",26,"dancing");  
   
                          //利用ArrayList类的add()方法添加元素  
           students.add(rose);  
                          students.add(jack);  
                          students.add(mimi);  
   
                          //利用ArrayList的Count属性查看该集合中的元素数量  
           int number = students.Count;   
                          Console.WriteLine("共有元素" + number + "个");  
   
                          //读取单个元素,因为存入ArrayList中的元素会变为Object类型,  
                         //所以，在读取时间，  
           Student stu = students[0] as Student;  
                          stu.say();  
   
                          //遍历元素 -- 通过索引   
           for(int i = 0;i < students.Count;i ++)   
                        {  
                               Student a = students[i] as Student;  
                               a.say();  
                        }  
                        //利用foreach循环  
          foreach(Object o in students)  
                       {  
                               Student b = o as Student;  
                               b.say();  
                      }  
   
                      //删除元素  通过索引删除   
         students.removeAt(0);  
                      //删除元素,    通过对象名   
         students.remove(jack);  
                     //清空元素  
         students.Clear();  
   
                      //我们知道，ArrayList的容量会随着我们的需要自动按照一定规律  
         //进行填充,当我们确定不再添加元素时，我们要释放多余的空间  
         //这就用到了Capacity属性和TrimtoSize()方法  
         //利用Capacity属性可以查看当前集合的容量     
         //利用TrimtoSize()方法可以释放多余的空间  
             
   
         //查看当前容量  
         int number = students.Capacity;   
                    //去除多余的容量  
        students.TrimtoSize();                       
             }  
} 

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