package demo1;public class Student {String name;int age;
}

package demo1;import java.util.ArrayList;
import java.util.Random;public class Demo1 {public static void main(String[] args) {ArrayList<Student> array = new ArrayList<Student>();   //定义ArrayList集合来盛放Student类    add(array);                            //添加数据到集合中printArrayList(array);                    //打印集合数据}//打印集合数据public static void printArrayList(ArrayList<Student> array) {for (int i = 0; i < array.size(); i++) {Student s = array.get(i);System.out.println(s.name+"\t"+s.age);}}//添加数据到集合中public static void add(ArrayList<Student> array) {Student s1 = new Student();s1.name = "张三";s1.age = 23;Student s2 = new Student();s2.name = "李四";s2.age= 24;array.add(s1);array.add(s2);}
}

package demo1;import java.util.ArrayList;
import java.util.Random;public class Demo1 {public static void main(String[] args) {ArrayList<Student> array = new ArrayList<Student>();addStudent(array);printArrayList(array);randomStudent(array);}//生成随机数，选择对应的学生，打印姓名和年龄public static void randomStudent(ArrayList<Student> array) {Random ran = new Random();int index = ran.nextInt(array.size());Student s = array.get(index);System.out.println("选择的学生是："+s.name+"\n年龄为："+s.age);}//打印集合public static void printArrayList(ArrayList<Student> array) {for (int i = 0; i < array.size(); i++) {Student s = array.get(i);System.out.println(s.name+"\t"+s.age);}}//向集合中添加Student数据public static void addStudent(ArrayList<Student> array) {Student s1 = new Student();s1.name = "张三";s1.age = 23;Student s2 = new Student();s2.name = "李四";s2.age = 24;Student s3 = new Student();s3.name = "王五";s3.age = 25;Student s4 = new Student();s4.name = "马六";s4.age = 26;array.add(s1);array.add(s2);array.add(s3);array.add(s4);}
}