Java - เรื่อง Constructor ของ SubClass และ SuperClass ครับ

public class People 
{
    private String name ;
    private int old ;
    private static int sum ;
    
    
    
    public People()
    {    
        this.sum = this.sum + 1 ; 

     }
    
    
    public People(String name , int old )
    {
       this.name = name  ;
       this.old = old ;
       this.sum = this.sum + 1 ; 
    }

   
     public void setName(String name)
     {
        this.name = name ;
     }
     
     public String getName()
     {
         return name ;
     }
     
     public void setOld(int old)
     {
         this.old = old ;
     }
     public int getOld()
     {
         return this.old ; 
     }

      public int getsum()
      {
         return this.sum ; 
      }
} // End Class PerPloe 

public class Job extends People
{
   private String job ; 
   
   
   public Job()
   {
      this.job = "" ; 
   } 
   public Job(String name ,  int old ,String job )
   {
      this.job = job ; 
      this.setName(name) ; 
      this.setOld(old) ;  
   } 
   public String getJob()
   {
      return this.job ; 
   }
}

public class Main 
{

  public static  void main(String[] arg)
  {
    System.out.println("Create People");  
    
    People p = new People();
    p.setName("Flap") ;
    p.setOld(21);
    System.out.println("People Name "+p.getName());  
    System.out.println("People Old "+p.getOld());
    System.out.println("Sum "+p.getsum());
    
    People p1 = new People("Jack",23);
    System.out.println("PerPloe Name "+p1.getName());  
    System.out.println("PerPloe Old "+p1.getOld());
    System.out.println("Sum "+p1.getsum());
    
    System.out.println("Create JOB");  
     Job jb = new Job("Nop",21,"CP");
      System.out.println("jb name "+jb.getName());
      System.out.println("jb old "+jb.getOld());
      System.out.println("jb Sum "+jb.getsum());


    
  }

}