Hero Assignment AOOP

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

class hero {
    protected String nama;
    protected String id;
    protected int hp;
    protected int atk;
    protected int lv;
    protected int sm;
    protected int bm;

    hero(){
    }

    public void lvUp(){

    }

    public String getNama() {
        return nama;
    }

    public void setNama(String nama) {
        this.nama = nama;
    }

    public int getHp() {
        return hp;
    }

    public void setHp(int hp) {
        this.hp = hp;
    }

    public int getAtk() {
        return atk;
    }

    public void setAtk(int atk) {
        this.atk = atk;
    }

    public int getLv() {
        return lv;
    }

    public void setLv(int lv) {
        this.lv = lv;
    }

    public int getSm() {
        return sm;
    }

    public void setSm(int sm) {
        this.sm = sm;
    }

    public int getBm() {
        return bm;
    }

    public void setBm(int bm) {
        this.bm = bm;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

}

 class swordman extends hero{
    swordman(String nama,String id){
        this.id=id;
        this.nama=nama;
        hp=100;
        atk=10;
        lv=1;
        sm=1;
        bm=0;
    }

    public void lvUp(){
        lv++;
        hp+=100;
        atk+=10;
        setSm(getSm() + 1);
    }

}

class archer extends hero{
    archer(String nama,String id){
        this.id=id;
        this.nama=nama;
        hp=100;
        atk=10;
        lv=1;
        sm=0;
        bm=1;
    }

    public void lvUp(){
        lv++;
        hp+=100;
        atk+=10;
        setBm(getBm() + 1);
    }
}

public class TugasAOOP {

    static Scanner x=new Scanner(System.in);
    static ArrayList<hero> hero=new ArrayList<hero>();
    static hero b;

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

    public static void main(String[] args) {
        menu();
    }

    public static void regis(){
        enter();
        String input,input2;
        int flag=0;
        do{
            flag=0;
            System.out.print("Masukan ID : ");
            input=x.nextLine();
            for (int j = 2; j < input.length(); j++) {
                if (Character.isDigit(input.charAt(j))) {
                    flag++;
                }
            }
        }while(input.length()!=5||flag!=3);
        System.out.print("Masukan Nama : ");
        input2=x.nextLine();
        do{
            flag=3;
            System.out.print("Pilih Hero [Swordman/Archer] : ");
            input=x.nextLine();
            if(input.equalsIgnoreCase("swordman")){
                b=new swordman(input,input2);
                flag=1;
                hero.add(b);
            }
            else if(input.equalsIgnoreCase("archer")){
                b=new archer(input,input2);
                flag=2;
                hero.add(b);
            }
        }while(flag==3);
        System.out.println("Pendaftaran Sukses  ");
        x.nextLine();
    }

    public static void view(){
        System.out.printf("|%s|%6s|%10s|\n","No.","ID","Nama");
        for (int i = 0; i < hero.size(); i++) {
            System.out.printf("|%d.|%6s|%10s|\n",i+1,hero.get(i).getId(),hero.get(i).getNama());
        }
    }

    public static void subMenu(int a){
        int flag=0;
        int p=0;
        do{
            enter();
            System.out.println("Menu");
            System.out.println("=====================");
            System.out.println("1. Training");
            System.out.println("2. View Stat");
            System.out.println("3. Back");
            do{
                System.out.print("Masukan Input : ");
                try{
                    flag=1;
                    p=x.nextInt();
                    x.nextLine();
                }
                catch(Exception e){
                    flag=0;
                    System.out.println("Input Salah");
                    x.nextLine();
                }
            }while(flag==0);
            switch(p){
                case 1:
                    enter();
                    hero.get(a).lvUp();
                    System.out.println("Sukses Level Up");
                    x.nextLine();
                    break;
                case 2:
                    enter();
                    System.out.println("ID : "+hero.get(a).getId());
                    System.out.println("Nama : "+hero.get(a).getNama());
                    System.out.println("Level : "+hero.get(a).getLv());
                    System.out.println("Attack : "+hero.get(a).getAtk());
                    System.out.println("HP : "+hero.get(a).getHp());
                    System.out.println("SwordMastery : "+hero.get(a).getSm());
                    System.out.println("BowMastery : "+hero.get(a).getBm());
                    x.nextLine();
                    break;
                case 3:
                    break;
                default:
                    subMenu(a);
                    break;
            }
        }while(p!=3);
    }

    public static void delete(int a){
        System.out.println("Deleting Data . . . ");
        System.out.println("Press <enter> to continue");
        hero.remove(a);
        x.nextLine();
    }

    public static void menu(){
        int a=0;
        int flag=0;
        do{
            enter();
            System.out.println("Menu");
            System.out.println("=====================");
            System.out.println("1. Registrasi");
            System.out.println("2. Load");
            System.out.println("3. Delete ID");
            System.out.println("4. Exit");
            do{
                System.out.print("Masukan Input : ");
                try{
                    flag=1;
                    a=x.nextInt();
                    x.nextLine();
                }
                catch(Exception e){
                    flag=0;
                    System.out.println("Input Salah");
                    x.nextLine();
                }
            }while(flag==0);
            switch(a){
                case 1:
                    regis();
                    break;
                case 2:
                    enter();
                    if(hero.isEmpty()){
                        System.out.println("Data Kosong");
                        x.nextLine();
                    }
                    else {
                        view();
                        do{
                            System.out.print("Masukan No ID : ");
                            try{
                                flag=1;
                                a=x.nextInt();
                                x.nextLine();
                            }
                            catch(Exception e){
                                flag=0;
                                System.out.println("Input Salah");
                                x.nextLine();
                            }
                        }while(flag==0||a>hero.size()||a<1);
                        a--;
                        subMenu(a);
                    }
                    break;
                case 3:
                    enter();
                    if(hero.isEmpty()){
                        System.out.println("Data Kosong");
                        x.nextLine();
                    }
                    else {
                        view();
                        do{
                            System.out.print("Masukan No ID : ");
                            try{
                                flag=1;
                                a=x.nextInt();
                                x.nextLine();
                            }
                            catch(Exception e){
                                flag=0;
                                System.out.println("Input Salah");
                                x.nextLine();
                            }
                        }while(flag==0||a>hero.size()||a<1);
                        a--;
                        delete(a);
                    }
                    break;
                case 4:
                    break;
                default:
                    menu();
                    break;
            }
        }while(a!=4);
    }
}