First Java Assignment

import java.util.Scanner;

public class Test {
    public static void main(String[] args) {
        /*Scanner x=new Scanner(System.in);
        System.out.println("Masukan Input : ");
        int a;
        a=x.nextInt();
        int b=a;
        for(int i=0;b>-1;i++){
            if(i<=b)
                System.out.print(" ");
            else if(i<=a)
                System.out.print("*");
            else{
                System.out.println();
                b--;
                i=0;
            }
        }
        */
        Scanner x=new Scanner(System.in);
        int pilih=0;
        String[] id;
        String[] nama;
        int[] nilai;
        int jumlah=0;
        id=new String[5];
        nama=new String[5];
        nilai=new int[5];
        do{
            for(int i=0;i<25;i++)
                System.out.println("");
            System.out.println("1. Input Student");
            System.out.println("2. See All Data");
            System.out.println("3. Edit Data");
            System.out.println("4. Exit");
            System.out.print("Masukan Input : ");
            pilih=x.nextInt();
            switch(pilih){
                case 1:
                    do{
                        System.out.print("How many student [1..5] :");
                        jumlah=x.nextInt();
                    }while(jumlah<1||jumlah>5);
                    for(int i=0;i<jumlah;i++){
                        do{
                            System.out.print("Please Input User ID[10] : ");
                            id[i]=x.next();
                        }while(id[i].length()!=10);
                        do{
                            System.out.print("Please Input User Name : ");
                            nama[i]=x.next();
                        }while(nama[i].equals(" "));
                        do{
                            System.out.print("Please Input User Score : ");
                            nilai[i]=x.nextInt();
                        }while(nilai[i]>100||nilai[i]<0);
                        System.out.println("");
                    }

                    break;
                case 2:
                    if(jumlah==0)
                    System.out.println("Data Tidak ada.");
                    else{
                        System.out.println("There is already "+jumlah+" data");
                        for(int i=0;i<jumlah;i++){
                            System.out.println((i+1)+". "+nama[i]);
                    }
                        int a;
                    do{
                        System.out.print("Please Input Student Number [1..."+(jumlah)+"] : ");
                        a=x.nextInt();
                    }while(a>jumlah||a<0);
                        System.out.println("Student With No. "+a+" is");
                        System.out.println("Student ID : "+id[a-1]);
                        System.out.println("Student Name : "+nama[a-1]);
                        System.out.println("Mark : "+nilai[a-1]);
                    }
                    x.nextLine();
                    x.nextLine();
                    break;
                case 3:
                    int a;
                    if(jumlah==0)
                    System.out.println("Data Tidak ada.");
                    else{
                        System.out.println("There is already "+jumlah+" data");
                        for(int i=0;i<jumlah;i++){
                            System.out.println((i+1)+". "+nama[i]);
                    }
                    do{
                        System.out.print("Please Input Student Number [1..."+(jumlah)+"] : ");
                        a=x.nextInt();
                    }while(a>jumlah||a<0);
                        System.out.println("Student With No. "+a+" is");
                        a--;
                        System.out.println("Student ID : "+id[a]);
                        System.out.println("Student Name : "+nama[a]);
                        System.out.println("Mark : "+nilai[a]);
                    do{
                        System.out.print("Please Input Student ID[10] : ");
                        id[a]=x.next();
                    }while(id[a].length()!=10);
                    do{
                        System.out.print("Please Input Student Name : ");
                        nama[a]=x.next();
                    }while(nama[a].equals(" "));
                    do{
                        System.out.print("Please Input Student Score : ");
                        nilai[a]=x.nextInt();
                    }while(nilai[a]>100||nilai[a]<0);
                    }
                    System.out.println("");
                    x.nextLine();
                    x.nextLine();
                    break;
                case 4:
                    break;
            }
        }while(pilih!=4);

    }
}