Java Inheritance with the use of super -

i'm trying create simple java inheritance program along use of super , keyword. showing here marks of student in 3 subjects 2 semesters sem1 , sem2. want show total marks ie. s1t(sem1 total), s2t(sem 2 total) , grand total..

//student record keeping system class sem1 {     int a,b,c,s1t,s1gt;     sem1(int a,int b,int c)     {         this.a=a;         this.b=b;         this.c=c;     }      void total()     {         s1t=a+b+c;         s1gt=s1t;     }       void display()     {         system.out.println("s11: "+a);         system.out.println("s12: "+b);         system.out.println("s13: "+c);         system.out.println("s1total: "+s1t);         system.out.println("s1gtotal: "+s1gt);         system.out.println("");     }      }  class sem2 extends sem1 {     int p,q,r,s2t,s2gt;     sem2(int p,int q,int r)     {         this.p=p;         this.q=q;         this.r=r;     }      void total()     {            s2t=p+q+r;         s2gt=s2t+s1t;         }       void display()     {         super.display();         system.out.println("s21: "+p);         system.out.println("s22: "+q);         system.out.println("s23: "+r);         system.out.println("s2total: "+s2t);         system.out.println("s2gtotal: "+s2gt);         system.out.println("");     }  } 

here main class

class studentrcd {     public static void main(string abc[])     {         sem1 obj = new sem1(10,20,30);         obj.total();         obj.display();          sem2 obj1 = new sem2(20,30,40);         obj1.total();         obj1.display();     } } 

error: constructor sem2 in class sem2 cannot applied given types; { ^ required: int,int,int found: no arguments reason: actual , formal argument lists differ in length

kindly me out here..

i don't think want 2 separate classes. 2 classes same, except computation of semester 2 total. may work better have 2 separate instances of 1 class, , compute full-year total separately.

if did want 2 classes, related inheritance, you'd either need call super() in sem2's constructor, because sem1 lacks default constructor. require provide additional values in sem2's constructor, since marks semester 1 differ of semester 2.

class sem2 extends sem1 {    int p,q,r,s2t,s2gt;    sem2( int a, int b, int c, int p,int q,int r)    {        super( a, b, c );        this.p=p;        this.q=q;        this.r=r;    }