Java Vector

import java.util.List;
import java.util.Vector;

public class Main {

    public static boolean isEmpty(Vector<String> v) {
        return v.isEmpty();
    }

    public static String addAll(Vector<String> v, String... s) {
        if(v.addAll(List.of(s))) return "Done";
        return "Failed";
    }

    public static String printAll(Vector<String> v) {
        String elements = "\n";
        for (String s: v) {
            elements += String.format("%d. %s\n", v.indexOf(s), s);
        }
        return elements;
    }

    public static String printAt(Vector<String> v, int position) {
        if (position < size(v)) return v.get(position);
        return null;
    }

    public static int atIndex(Vector<String> v, String s) {
        if (v.contains(s)) return v.indexOf(s);
        return -1;
    }
    
    public static int size(Vector<String> v) {
        return v.size();
    }

    public static void main(String[] args) {
        Vector<String> mahasiswa = new Vector<>();

        System.out.println("Apakah elemen kosong        : "+ isEmpty(mahasiswa));
        System.out.println("Tambah beberapa elemen      : "+ addAll(mahasiswa, "Adi", "Budi", "Cindy"));
        System.out.println("Tampilkan semua elemen      : "+ printAll(mahasiswa));
        System.out.println("Tampilkan elemen pada posisi: "+ printAt(mahasiswa,2));
        System.out.println("Cari posisi elemen          : "+ atIndex(mahasiswa, "Adi"));
        System.out.println("Jumlah elemen saat ini      : "+ size(mahasiswa));
    }
}