Basic Inheritance & Function Overloading

import java.util.Scanner;

public class Inheritance {
    static class mahasiswa{
        String nama;
        int nim;

        mahasiswa(){///construction
            nama="no name";
            nim=0;
        }
        void setData(int nim,String nama){
            this.nama=nama;
            this.nim=nim;
        }
        String getNama(){
            return nama;
        }
        int getNim(){
            return nim;
        }
    }

    static class jurusan extends mahasiswa{//inheritance
        String jurusan;
        int sem;

        jurusan(){
            jurusan="-";
            sem=0;
        }
        void setData(String jurusan,int sem){//function overloading
            this.jurusan=jurusan;
            this.sem=sem;
        }
        String getJurusan(){
            return jurusan;
        }
        int getSem(){
            return sem;
        }
    }

    static void enter(){
        for (int i = 0; i < 25; i++) {
            System.out.println(" ");
        }
    }

    static Scanner x=new Scanner(System.in);//cin/scanf/get

    static public void main(String[] args) {
        jurusan mhs=new jurusan();
        enter();
        System.out.println("Selemat datang di program pendaftaran semester,");
        System.out.print("Press <enter> to continue ");
        x.nextLine();
        regis(mhs);

    }

    static void regis(jurusan mhs){
        enter();
        String nama,jurusan;int nim=0,sem=0;
        boolean flag=true;
        do{
            System.out.print("Masukan Nama[tidak boleh mengandung angka] : ");
            nama=x.nextLine();
            if(nama.matches(".*\\d.*"))
                System.out.println("Input tidak boleh mengandung angka");
            else
                flag=false;
        }while(flag);
        enter();
        do{
            System.out.print("Masukan Nim[8 digit] :");
            try{
                nim=x.nextInt();
                x.nextLine();
            }catch(Exception e){
                System.out.println("Input harus numerik");
                x.nextLine();
            }
            if(nim>100000000||nim<10000000)
                System.out.println("Nim Tidak valid");
            else
                flag=true;
        }while(!flag);
        mhs.setData(nim, nama);
        enter();
        //System.out.println("Selamat Datang, "+mhs.getNama()+"("+mhs.getNim()+")");
        do{
            System.out.print("Masukan Jurusan[TI/SI/GAT/MAT] :");
            jurusan=x.nextLine();
            if(jurusan.equals("TI")||jurusan.equals("SI")||
                    jurusan.equals("GAT")||jurusan.equals("MAT"))
                flag=false;
            else
                System.out.println("Jurusan salah!");
        }while(flag);
        enter();
        do{
            System.out.print("Masukan Semester[2-7] :");
            try{
                sem=x.nextInt();
                x.nextLine();
            }catch(Exception e){
                System.out.println("input harus angka");
                x.nextLine();
            }
            if(sem<2||sem>7)
                System.out.println("Semester salah!");
            else
                flag=true;
        }while(!flag);
        mhs.setData(jurusan, sem);
        enter();
        System.out.println("Nama : "+mhs.getNama());
        System.out.println("Nim : "+mhs.getNim());
        System.out.println("Jurusan : "+mhs.getJurusan());
        System.out.println("Semester : "+mhs.getSem());
        do{
            System.out.print("Apakah data anda sudah benar[Y/N]?");
            nama=x.nextLine();
            if(nama.toUpperCase().equals("N")){
                enter();
                System.out.println("Memasukan data ulang");
                System.out.print("Press <enter> to restart");
                x.nextLine();
                regis(mhs);
        break;
            }
            else if(nama.toUpperCase().equals("Y")){
                System.out.println("Terima Kasih Atas waktu anda!");
                System.out.println("Press <enter> to exit");
                flag=false;
                x.nextLine();
            }
            else
                System.out.println("Input Salah!");
        }while(flag);
    }
}