ArrayList

import java.util.*;public class ArrayListdemo{         public static void main(String[] args){                         //构造一个指定容量为10的数组                ArrayList<Student>  strArr=new ArrayList<Student>(10);                    strArr.add(new Student("张三",23,123456,"男"));                    strArr.add(new Student("张三",23,123456,"男"));                    strArr.add(new Student("李四",23,123456,"男"));                    strArr.add(new Student("王五",23,123456,"男"));                     strArr.add(new Student("张三",23,123456,"男"));                    //返回当前元素的数量；                    int x=strArr.size();                    System.out.println(x);                    //get(int index) 返回此列表中指定位置上的元素。                     Student stu=strArr.get(3);                     System.out.println(stu.getName());                     //add(int index, E element)     将指定的元素插入此列表中的指定位置。                     strArr.add(5,new Student("jack",23,123456,"男"));                     strArr.add(6,new Student("jodan",23,123456,"男"));                    //在4位置插入一个元素，4后面的元素都向后移动一位                     strArr.add(4,new Student("King",23,123456,"男"));                     Student stu1=strArr.get(6);                     System.out.println(stu1.getName());         }}/**自定义学生类**/ class Student{    private String name;    private int age ;    private int stuNumber;    private String gender;    //无参构造器    public Student(){    }    //有参构造器    public Student(String name,int age,int stuNumber,String gender){             this.name=name;             this.age =age;             this.stuNumber=stuNumber;             this.gender=gender;                  }    public String getName(){        return name;    }    public int getAge(){        return age ;    }    public int getStuNumber(){        return stuNumber;    }    public String getGender(){        return gender;    }    public void setName(String n){        name=n;    }    public void setAge(int a){            age=a;    }    public void setStuNumber(int s){           stuNumber=s;    }    public void setGender(String g){            gender=g;    }}

运行结果：
5
王五
jack