JAVA定义一个学生类Student，存在三个变量，分别是学号num，姓名name和课程lesson，其中课程对全班同学共享

定义一个学生类Student，存在三个变量，分别是学号num，姓名name和课程lesson，其中课程对全班同学共享，包含方法如下：1.构造方法 Student(),用来输出“开始新学期的课程！”2.构造方法 Student(String num, String name),首先调用无参数构造方法，随后初始化变量。3.成员方法 String showInfo(),用来输出“学号XXX，姓名XXX开始XXX课程。”4.在主类中定义两个学生，实现以上信息的输出。

public class Student {
    
    private String num;
    private String name;
    public static String lesson;
    
    public Student() {
        System.out.println("开始新学期的课程！");
    }
    
    public Student(String num,String name) {
        this();
        this.num = num;
        this.name = name;
    }
    
    public String showInfo() {
        return "学号"+this.num+",姓名"+this.name+"开始"+lesson+"课程";
    }
}

public static void main(String[] args) {
        // TODO Auto-generated method stub
        Student student1 = new Student("1","张三");
        student1.lesson="Java";
        String info1 = student1.showInfo();
        System.out.println(info1);
        
        Student student2 = new Student("2","李四");
        String info2 = student2.showInfo();
        System.out.println(info2);
    }

public class Student{
  String num;
  String name;
  static String lesson;
  public Student(){
    System.out.println("开始新学期的课程:"+lesson);
    num="1001";
    name = "张三";
  }
  public Student(String num, String name){
    this.num = num;
    this.name = name;
  }
  public String showInfo(){
      return "学号"+num+"，姓名"+name+"开始"+lesson+"课程。";
  }
}
public class Test(){
    public static void(String args[]){
      Student s1 = new Student();
      System.out.println(s1.showInfo());
      Student s2 = new Student("1002","李四");
      System.out.println(s2.showInfo());

  }
}