KRS-OOP

package mahasiswa;

class mhs {
    private int npm;
    private String nama;

    public mhs() {
        npm = 0;
        nama = "";
    }

    public mhs(int n, String nm) {
        npm = n;
        nama = nm;
        System.out.println("Constructor Mahasiswa: " + npm + " " + nama);
    }

    public String cetak() {
        return npm + " " + nama;
    }
}

class matakuliah {
    private String kode;
    private String nama_mk;
    public static int jumlahmk;

    public matakuliah() {
        kode = "";
        nama_mk = "";
    }

    public matakuliah(String k, String nm) {
        kode = k;
        nama_mk = nm;
        System.out.println("Constructor Mata Kuliah: " + kode + " " + nama_mk);
        jumlahmk++;
    }

    public String cetak() {
        return nama_mk;
    }

    public String getcode() {
        return kode;
    }
}

class krs {
    private mhs peserta;
    private matakuliah mk;
    public static int jumlahkrs;

    public krs(mhs m, matakuliah k) {
        peserta = new mhs();
        peserta = m;
        mk = new matakuliah();
        mk = k;
        jumlahkrs++;
    }

    public String getkode() {
        return mk.getcode();
    }

    public String cetak() {
        return peserta.cetak();
    }
}

public class Mahasiswa {

    /**
     * @param args
     *            the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        mhs si1 = new mhs(123, "budi");
        mhs si2 = new mhs(456, "amin");
        mhs si3 = new mhs(789, "dedi");
        matakuliah mk[] = new matakuliah[2];
        mk[0] = new matakuliah("1", "BP");
        mk[1] = new matakuliah("2", "PTI");
        krs krsku[] = new krs[5];
        System.out.println("\nProgram Mahasiswa Kuliah");
        krsku[0] = new krs(si1, mk[0]); // mhs si mengambil matkul mk
        krsku[1] = new krs(si1, mk[1]);
        krsku[2] = new krs(si2, mk[0]);
        krsku[3] = new krs(si3, mk[0]);
        krsku[4] = new krs(si3, mk[1]);
        // menampilkan berdasarkan kode mata kuliahnya
        System.out.println("Jumlah KRS: " + krs.jumlahkrs + " record");
        System.out.println("Jumlah mata kuliah: " + mk[1].jumlahmk + "\n");

        for (int i = 0; i < mk[1].jumlahmk; i++) {
            System.out.println("Nama MK: " + mk[i].cetak());
            for (int j = 0; j < krsku[4].jumlahkrs; j++) {
                if ((krsku[j].getkode().compareTo(Integer.toString(i + 1))) == 0)
                    System.out.println(krsku[j].cetak());
            }
            System.out.println();
        }
    }
}