id.java: public class id{ private String nama; private String alamat; private int umur; public id(String var1, String var2, int var3){ nama=var1; alamat=var2; umur=var3; } public void print(){ System.out.println("Nama:"+nama); System.out.println("Alamat:"+alamat); System.out.println("Umur:"+umur); } public String getNama(){ return nama; } public String getAlamat(){ return alamat; } } mahasiswa.java: import java.util.ArrayList; public class mahasiswa extends id{ private String NRP; private ArrayList<makul> m_k; private ArrayList<buku> bk; public mahasiswa(String var1, String varNRP, String var2, int var3){ super(var1, var2, var3); NRP = varNRP; m_k = new ArrayList<makul>(); bk = new ArrayList<buku>(); } public void addMK(makul varMK){ m_k.add(varMK); } public void dropMK(makul varMK){