我所理解的ArrayList

1.定义：ArrayList是一个动态数组，该数组的容量能任意变化（增大或减少）。
2.使用方法：ArrayList <类名1> 数组名=new ArrayList<类名2>();
（注意：类名1和类名2是相同的，类名2可以省略）
3.例子：

例子1
package T1;

import java.util.ArrayList;

public class demo {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        ArrayList<String> str = new ArrayList<String>();

        str.add("hey");
        str.add("hello");
        str.add("hi");

        System.out.println(str);

        for (int i = 0; i < str.size(); i++) {
            // String s = str.get(i);
            System.out.print(str.get(i) + " ");

        }

    }

}

例子2
//创建一个类
package P02;

public class Student {
    String name;
    String gender;
    int age;
    String classname;

    Student() {
        // TODO Auto-generated constructor stub
    }

    /**
     * 
     * @param name
     * @param gender
     * @param age
     * @param classname
     */
    public Student(String name, String gender, int age, String classname) {
        this.name = name;
        this.gender = gender;
        this.age = age;
        this.classname = classname;

    }

}
//利用创建好的类创建数组
package P02;

import java.util.ArrayList;

public class Text {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        ArrayList<Student> students = new ArrayList<Student>();

        Student t1 = new Student("jack", "男", 22, "2班");
        Student t2 = new Student("frank", "男", 23, "3班");
        Student t3 = new Student("marry", "女", 24, "4班");

        students.add(t1);
        students.add(t2);
        students.add(t3);


        for (int i = 0; i < students.size(); i++) {
            Student s = students.get(i);
            System.out.println("学生姓名："+s.name+" 学生性别："+s.gender+" 学生年龄："+s.age+" 学生班级："+s.classname);

        }
        /*for (Student stu : students) {
            System.out.println(stu.classname+"--"+stu.gender);

        }
*/
    }

}