具体见注释：

//1.定义一个学生类，后期用于创建对象封装学生数据
//2.定义一个集合对象用于装学生对象

通过用学生编号不断的循环查询学生信息；

由两部分组成；

1.主代码“

ArrayListDemo.java

”

2.Student.java  学生类--模板

------------

Student.java 的代码：

package student;

import com.sun.org.apache.xpath.internal.objects.XString;

public class Student {
    private String studyid;
    private String name;
    private int age;
    private String className;


    public Student() {   //设置无参构造器
    }

    public Student(String studyid, String name, int age, String className) {  //设置有参构造器
        this.studyid = studyid;
        this.name = name;
        this.age = age;
        this.className = className;
    }

    public String getStudyid() {
        return studyid;
    }

    public void setStudyid(String studyid) {
        this.studyid = studyid;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getClassName() {
        return className;
    }

    public void setClassName(String className) {
        this.className = className;
    }


}

2.主代码：

package student;

import java.util.ArrayList;
import java.util.Scanner;

public class ArrayListDemo {

    public static void main(String[] args) {
        //1.定义一个学生类，后期用于创建对象封装学生数据
        //2.定义一个集合对象用于装学生对象

        ArrayList<Student> stus=new ArrayList<>();

        //把一个学生实例对象存储到 stu中


        stus.add(new Student("202001","猪八戒",900,"天宫一班"));
        stus.add(new Student("202002","孙悟空",800,"天宫五班"));
        stus.add(new Student("202003","沙和尚",1900,"天宫二班"));
        stus.add(new Student("202004","白龙马",990,"天宫三班"));

        //3.遍历集合中的每个学生对象，展示其数据

        for (int i = 0; i <stus.size() ; i++) {

            Student s=stus.get(i);  //获取每个学生对象

            System.out.println(s.getStudyid()+"\t\t"+s.getName()+"\t\t"+s.getAge()+"\t\t"+s.getClassName());


        }

        //4.让用户不断地输入学号，可以搜索出该学生对象信息并展示出来（独立成方法）

        Scanner sc=new Scanner(System.in);

        //idea中快捷键是ctrl+ait+T

        while (true) {
            System.out.println("请输入你要查询的学生的学号:");
            String id=sc.next();
            Student s=getStudentById(stus,id);
            // 判断学号是否存在
            if(s==null){
                System.out.println("查无此人！");

            }else{
                //找到了该学生对象了，信息如下：
                System.out.println(s.getStudyid()+"\t\t"+s.getName()+"\t\t"+s.getAge()+"\t\t"+s.getClassName());
            }
        }


    }
    // 根据学生类，去集合中找出学生对象并返回
    public static Student getStudentById(ArrayList<Student> stus1,String studyId){
        for (int i = 0; i < stus1.size(); i++) {
            Student s=stus1.get(i);
            if(s.getStudyid().equals(studyId)){
                return s;
            }


        }
        return null;


    }
}