Ai rành về C++ vào giải thích cho em bài này

[thienduong_khongtinhyeu34]

Code: #include
#include
#include
#include // dinh nghia cac lop ho tro cac phep toanc ho dong nhap xuat du lieu tren cac chuoi chua trong tap tin ben ngoai
#include
#include // bao gom cac ham dung de phan lop cac ki tu boi cac kieu hay dung de chuyen doi giua chu hoa va chu thuong
#include
#include


/*** class MAT HANG ***/
class mathang
{
friend class hoadon;
private:
char *mahang;
char *tenhang;
int soluong;
long int gia;
static int tongsohang; //tong so hang
static mathang *cachang[100]; //danh sach luu tru cac mat hang
static const char *tephang;
public:
mathang(char * ma,char *ten,int sl, long int g) //khai bao ham co doi
{
mahang=strdup(ma); //strdup dung de cap phat 1 bo nho vua du cho xau vua dua vao va copy xau co vao vung nho vua cap phat
tenhang=strdup(ten);
this->soluong=sl;
this->gia=g;
}
static void themhang(); //them mat hang
static void timhang(); //tim mat hang theo ma
static void lietkehang(); //liet ke mat hang
static void nhaphang();// nhap them lam tang so luong cua mat hang
static void suahang(); //sua thong tin ve mat hang
static void xoahang();// xoa mot mat hang
void hienmothang(); //hien thi mot mat hang (la 1 phan cua liet ke mat hang)
static void ghihang(); //ghi mat hang vao tep
static void dochang(); //doc mat hang tu tep ra
};

const char* mathang::tephang="hang.txt";
int mathang::tongsohang=0;
mathang* mathang::cachang[100];

void mathang::themhang()
{
char ma[4];//ma hang
char ten[15];// ten mat hang
int sl;//so luong
long g;//gia mat hang
cout<<"Nhap vao ma mat hang: ";
fflush(stdin);
gets(ma);
int dem=0;
for(int i=0;i if(strcmp(cachang->mahang,ma)==0)
dem++;
if(dem!=0)
cout<<"\nMa mat hang nay da duoc nhap, ban phai nhap ma so khac!\n\n";
else
{
cout<<"Nhap vao ten mat hang: ";
fflush(stdin);
gets(ten);
cout<<"Nhap vao so luong mat hang: ";
cin>>sl;
cout<<"Nhap vao gia cua mat hang: ";
cin>>g;

cachang[tongsohang]=new mathang(ma,ten,sl,g);
tongsohang++;
cout<<"\nMat hang nay da duoc them vao !\n\n";
}
}

void mathang::suahang()
{
char ma[4];
char masua[4];
char ten[15];
int sl;
long g;
int i,j;
cout<<"Nhap vao ma mat hang can sua: ";
fflush(stdin);
gets(ma);
for(j=0;j if(strcmp(cachang[j]->mahang,ma)==0)
{
cout<<"Sua ma mat hang: ";
fflush(stdin);
gets(masua);
cout<<"Sua ten mat hang: ";
fflush(stdin);
gets(ten);
cout<<"Sua so luong mat hang: ";
cin>>sl;
cout<<"Sua gia cua mat hang: ";
cin>>g;
for(i=0;i if(strcmp(cachang->mahang,ma)==0)
{
strcpy(cachang->mahang,masua);
strcpy(cachang->tenhang,ten);
cachang->soluong=sl;
cachang->gia=g;
break;
}
cout<<"Ban da sua xong !\n\n";break;
}
if(j==tongsohang)
cout<<"Khong co ma hang nao nhu vay!\n\n";
}


void mathang::xoahang()
{
char ma[4];
int x;
int i;
cout<<"Nhap vao ma hang can xoa :";
fflush(stdin);
gets(ma);
for (i=0;i if(strcmp(cachang->mahang,ma)==0)
{
x=i;
break;
}
if(i==tongsohang)
cout<<"Khong co ma khach nao nhu vay !\n\n";
else
{
for(i=x;i cachang=cachang[i+1];
delete cachang[tongsohang-1];
cout<<"Da xoa mat hang co ma "< tongsohang--;
}
}

void mathang::nhaphang()
{
int x;
char ma[4];
cout<<"Nhap ma hang can tang so luong: ";
gets(ma);
cout<<"Nhap vao so luong can tang cua mat hang co ma "< cin>>x;
for(int i=0;i if(strcmp(cachang->mahang,ma)==0)
{
cachang->soluong+=x;
cout<<"Da nhap hang xong !\n\n";
break;
}
}

void mathang::lietkehang()
{
cout.setf(ios::left);
cout<<"\n\n";
cout<<"||====================================================||\n";
cout<<"|| DANH SACH CAC MAT HANG ||\n";
cout<<"||====================================================||\n";
cout<<" ";
cout.width(15);
cout<<"Ma hang";
cout.width(15);
cout<<"Ten mat hang";
cout.width(15);
cout<<"So luong";
cout.width(10);
cout<<"Gia \n" ;
for(int i=0;i {
cout<<" ";
cachang->hienmothang();
cout< }
cout<<"\n\n";
}

void mathang::hienmothang()
{
cout.setf(ios::left); //in thang theo le trai
cout.width(15); //do dai cua o nho chua x=15 co tac dung voi lenh ngay sau no
cout< cout.width(15);
cout< cout.width(15);
cout< cout.width(10);
cout<}

void mathang::timhang()
{
int i,dem=0;
char ma[4];
cout<<"\nNhap vao ma mat hang can tim: ";
gets(ma);
for( i=0;i if(strcmpi(ma,cachang->mahang)==0)
dem++ ;
if(dem==0)
cout<<"Khong co mat hang co ma so nay!\n\n";
for( i=0;i if(strcmpi(ma,cachang->mahang)==0)
{
cout.setf(ios::left);
cout<<"\n\n";
cout<<"||====================================================||\n";
cout.width(15);
cout<<"||Ma hang";
cout.width(15);
cout<<"Ten mat hang";
cout.width(15);
cout<<"So luong";
cout.width(10);
cout<<"Gia ||\n\n" ;
cachang->hienmothang();
cout< }
}

void mathang::dochang()
{
ifstream is(tephang);
while(1)
{
char mahang[4];
is.getline(mahang,sizeof(mahang));
char tenhang[15];
is.ignore();
is.getline(tenhang,sizeof(tenhang));
int soluong;
long gia;
is>>soluong>>gia;
is.ignore();
if(is.gcount()==0) break;
else
cachang[tongsohang++] =new mathang(mahang,tenhang,soluong,gia);
}
}

void mathang::ghihang()
{
ofstream os(tephang);
for(int i=0;i {
os<->mahang< os<->tenhang< os<->soluong< os<->gia< }
}


//*** class khach hang ***
class khachhang
{
friend class hoadon;
private:
char *makhach;
char *tenkhach;
char *dtkhach;
static int tongsokhach;//tong so khach
static khachhang *cackhach[100]; //danh sach luu tru cac khach
static const char* tepkhach;
public:
khachhang(char *ma,char *ten,char *dt)
{
makhach=strdup(ma);
tenkhach=strdup(ten);
dtkhach=strdup(dt);
}
static void themkhach(); //phuong thuc them khach hang
static void lietkekhach(); //phuong thuc liet ke khach hang
static void timkhach(); //tim mot khach hang theo ma
static void suakhach(); //sua thong tin khach
static void xoakhach(); //xoa mot khach hang
void hienmotkhach(); //hien thi mot khach (la 1 phan cua liet ke khach hang)
static void ghikhach(); //ghi khach hang vao tep
static void dockhach(); //doc khach hang tu teo ra
};

const char* khachhang::tepkhach="khach.txt";
int khachhang::tongsokhach=0;
khachhang* khachhang::cackhach[100];

void khachhang::themkhach()
{
char ma[4];
char ten[25];
char dt[15];
cout<<"Nhap vao ma khach :";
fflush(stdin);
gets(ma);
int dem=0;
for (int i=0;i if(strcmp(cackhach->makhach,ma)==0)
dem++;

if(dem!=0)
cout<<"\nMa khach nay da duoc nhap, ban phai nhap ma so khac!\n\n";

else
{
cout<<"Nhap vao ten khach hang: ";
fflush(stdin);
gets(ten);
cout<<"Nhap vao so dien thoai khach hang: ";
fflush(stdin);
gets(dt);

cackhach[tongsokhach]=new khachhang(ma,ten,dt);
tongsokhach++;
cout<<"\nKhach hang nay da duoc them vao !\n\n";
}
}

void khachhang::suakhach()
{
char ma[4];
char masua[4];
char ten[25];
char dt[15];
int i,j;
cout<<"Nhap vao ma khach hang can sua: ";
fflush(stdin);
gets(ma);
for(j=0;j if(strcmp(cackhach[j]->makhach,ma)==0)
{
cout<<" Sua ma khach hang: ";
fflush(stdin);
gets(masua);
cout<<" Sua ten khach hang: ";
fflush(stdin);
gets(ten);
cout<<" Sua so dien thoai khach hang: ";
fflush(stdin);
gets(dt);
for(i=0;i if(strcmp(cackhach->makhach,ma)==0)
{
strcpy(cackhach->makhach,masua);
strcpy(cackhach->tenkhach,ten);
strcpy(cackhach->dtkhach,dt);
break;
}
cout<<"Ban da sua xong !\n\n";break;
}
if(j==tongsokhach)
{
cout<<"Khong co ma khach nao nhu vay!\n\n";
}
}

void khachhang::xoakhach()
{
char ma[4];
int x;
int i;
cout<<" Nhap vao ma khach can xoa :";
fflush(stdin);
gets(ma);
for (i=0;i if(strcmp(cackhach->makhach,ma)==0)
{
x=i;
break;
}
if(i==tongsokhach)
cout<<"Khong co ma khach nao nhu vay !\n\n";
else
{
for(i=x;i cackhach=cackhach[i+1];
delete cackhach[tongsokhach-1];
cout<<"Da xoa khach hang co ma "< tongsokhach--;
}
}

void khachhang::lietkekhach()
{
cout.setf(ios::left);
cout<<"\n\n";
cout<<"||====================================================||\n";
cout<<"|| DANH SACH CAC KHACH HANG ||\n";
cout<<"||====================================================||\n";
cout.width(15);
cout<<"||Ma khach";
cout.width(25);
cout<<"Ten khach";
cout.width(15);
cout<<"Dien thoai ||\n\n\n" ;

for(int i=0;i {
cackhach->hienmotkhach();
cout< }
}

void khachhang::hienmotkhach()
{
cout.setf(ios::left);
cout.width(15);
cout< cout.width(25);
cout< cout.width(15);
cout<}

void khachhang::timkhach()
{
int i,dem=0;
char ma[4];
cout<<"\n Nhap vao ma khach hang can tim: ";
gets(ma);
for( i=0;i if(strcmp(ma,cackhach->makhach)==0)
dem++ ;
if(dem==0)
cout<<"Khong co khach hang co ma so nay!\n\n";
for( i=0;i if(strcmp(ma,cackhach->makhach)==0)
{
cout.setf(ios::left);
cout.width(15);
cout<<"\n\n";
cout<<"||====================================================||\n";
cout<<"||Ma khach";
cout.width(25);
cout<<"Ten khach";
cout.width(15);
cout<<"Dien thoai ||\n\n" ;
cackhach->hienmotkhach();
cout< }
}

void khachhang::dockhach()
{
ifstream is(tepkhach);
while(1)
{
char ma[4];
is.getline(ma,sizeof(ma));
char ten[25];
is.ignore();
is.getline(ten,sizeof(ten));
char dt[15];
is.getline(dt,sizeof(dt));
if(is.gcount()==0) break;
else
cackhach[tongsokhach++] =new khachhang(ma,ten,dt);
}
}

void khachhang::ghikhach()
{
ofstream os(tepkhach);
for(int i=0;i {
os<->makhach< os<->tenkhach< os<->dtkhach< }
}


//*** class hoa don ***

class hoadon
{
friend class mathang;
friend class khachhang;
private:
char *mahoadon;
char *mamathang;
char *makhachhang;
int soluong;
long thanhtien;
static int sohoadon;//tong so hoa don
static hoadon*cachoadon[100];// danh sach cac hoa don
static const char *tephoadon;
public:
hoadon(char *ma0,char*ma1,char*ma2,int sl,long tien)
{
mahoadon=strdup(ma0);
mamathang=strdup(ma1);
makhachhang=strdup(ma2);
soluong=sl;
thanhtien=tien;
}
static void laphoadon(); //tao 1 hoa don moi
void hienhoadon(); //hien 1 hoa don (la 1 phan cua danh sach hoa don)
static void danhsachcachoadon(); //hien tat ca hoa don
static void suahoadon(); // sua hoa don
static void xoahoadon(); //xoa hoa don
static void timhoadon(); //tim hoa don
static void dochoadon(); //doc hoa don tu tep
static void ghihoadon(); //ghi hoa don vao tep
};

const char* hoadon::tephoadon="hoadon.txt";
hoadon*hoadon::cachoadon[100];
int hoadon::sohoadon=0;

void hoadon::laphoadon()

{
char mahoadon[50];
char mamathang[50];
char makhachhang[50];
int soluong;
long thanhtien=0;
int i,j;
int dem1=0,dem2=0,dem3=0,count=1;
cout<<"\nNhap vao ma hoa don: ";
fflush(stdin);
gets(mahoadon);
for(i=0;i if(strcmp(mahoadon,hoadon::cachoadon->mahoadon)==0)
{
dem3++;
break;
}
if(dem3!=0)
{
cout<<"Ma hoa don nay da co, ban hay nhap ma hoa don khac\n";

}
else
{
cout<<"Nhap vao ma mat hang can ban: ";
fflush(stdin);
gets(mamathang);
/*dung bien j de khong bi trung bien i, giup xac dinh
vi tri mat hang thu j de san sang thay doi so luong,
duoc lam ngay ben duoi */
for(j=0;j if(strcmp(mamathang,mathang::cachang[j]->mahang)==0)
{
dem1++;
break;
}
if(dem1==0)
{
cout<<"\nKhong co ma mat hang nay !\n";
count=0;
}
else
{

cout<<"Nhap vao ma khach hang can mua: ";
fflush(stdin);
gets(makhachhang);


for(i=0;i if(strcmp(makhachhang,khachhang::cackhach->makhach)==0)
{
dem2++;
break;
}
if(dem2==0)
{
cout<<"\nKhong co ma khach hang nay !\n";
count=0;
}
else
{
/*nhap vao gia tri so lung ban ra cua mot mat hang, se duoc tru di
trong so luong cua mot mat hang */

if((dem1!=0)&&(dem2!=0))
{
cout<<"Nhap vao so luong hang can ban: ";
cin>>soluong;
/*lay gia tri j de xac dinh mat hang thu may*/
if((mathang::cachang[j]->soluong)>=soluong)
{
mathang::cachang[j]->soluong-=soluong;
thanhtien=(mathang::cachang[j]->gia)*soluong;
}
else
if((mathang::cachang[j]->soluong)<=0)
{
cout<<"Rat tiec, da het hang !\n\n";
count=0;
}
else
{
cout<<"So luong mat hang nay khong du de ban !\n\n";
count=0;
}
}


if(count==1)
{
cachoadon[sohoadon]=new hoadon(mahoadon,mamathang,makhachhang,soluong,thanhtien);

sohoadon++;

cout<<"\nDa ban mat hang co ma "< cout<<"\ncho khach hang co ma "< cout<<"\nvoi so luong la: "< cout<<"\nTong so tien phai tra la: "< cout<<"\nDa duoc ghi vao hoa don co ma: "< }
}
}
}
};

void hoadon::suahoadon()
{
char mahoadon[10];
char mahoadonsua[10];
char makhachhang[10];
char mamathang[15];
int soluong,x;
long thanhtien;
int i,j;
cout<<"Nhap vao ma hoa don can sua: ";
fflush(stdin);
gets(mahoadon);
for(j=0;j if(strcmpi(cachoadon[j]->mahoadon,mahoadon)==0)
{
for(i=0;i if(strcmpi(cachoadon->mahoadon,mahoadon)==0)
{
x=cachoadon->soluong;break;
}
cout<<" Sua ma hoa don: ";
fflush(stdin);
gets(mahoadonsua);
cout<<" Sua ma mat hang: ";
fflush(stdin);
gets(mamathang);
cout<<" Sua ma khach hang: ";
fflush(stdin);
gets(makhachhang);
cout<<" Sua so luong hang da mua:";
cin>>soluong;
for(int k=0;k if(strcmp(cachoadon->mamathang,mathang::cachang[k]->mahang)==0)
{
mathang::cachang[k]->soluong+=x;
}
for(j=0;j if((mathang::cachang[j]->soluong)>=soluong)
{
mathang::cachang[j]->soluong-=soluong;
thanhtien=(mathang::cachang[j]->gia)*soluong;
}

for(i=0;i if(strcmp(cachoadon->mahoadon,mahoadon)==0)
{
strcpy(cachoadon->mahoadon,mahoadonsua);
strcpy(cachoadon->makhachhang,makhachhang);
strcpy(cachoadon->mamathang,mamathang);
cachoadon->soluong=soluong;
cachoadon->thanhtien=thanhtien;
break;
}
cout<<"Ban da sua xong !\n";break;
}
if(j==sohoadon)
{
cout<<"Khong co ma hoa don nao nhu vay!\n";
}
}

void hoadon::hienhoadon()
{
cout.setf(ios::left);
cout.width(15);
cout< cout.width(15);
cout< cout.width(15);
cout< cout.width(15);
cout< cout.width(20);
cout<}

void hoadon::danhsachcachoadon()
{
cout.setf(ios::left);
cout<<"\n\n";
cout<<"||====================================================================||\n";
cout<<"|| DANH SACH CAC HOA DON ||\n";
cout<<"||====================================================================||\n";
cout.width(15);
cout<<"||Ma hoa don";
cout.width(15);
cout<<"Ma mathang";
cout.width(15);
cout<<"Ma khach hang";
cout.width(15);
cout<<"So luong";
cout.width(25);
cout<<"Thanh tien||\n\n";
for(int i=0;i {
cachoadon->hienhoadon();
}
}

void hoadon::xoahoadon()
{
char mahoadon[5];
int x;
int i;
cout<<"Nhap vao ma hoa don can xoa :";
fflush(stdin);
gets(mahoadon);
for (i=0;i if(strcmpi(cachoadon->mahoadon,mahoadon)==0)
{
x=i;
break;
}
if(i==sohoadon)
cout<<"Khong co ma hoa don nao nhu vay !\n\n";
else
{
for(i=x;i cachoadon=cachoadon[i+1];
delete cachoadon[sohoadon-1];
cout<<"Da xoa hoa don co ma "< sohoadon--;
}
}

void hoadon::timhoadon()
{
int i,dem=0;
char mahoadon[4];
cout<<"\nNhap vao ma mat hang can tim: ";
gets(mahoadon);
for( i=0;i if(strcmpi(mahoadon,cachoadon->mahoadon)==0)
dem++ ;
if(dem==0)
cout<<"Khong co hoa don nao co ma so nay!\n\n";
for( i=0;i if(strcmpi(mahoadon,cachoadon->mahoadon)==0)
{
cout<<"||====================================================||\n";
cout.width(15);
cout<<"||Ma hoa don";
cout.width(15);
cout<<"Ma mathang";
cout.width(15);
cout<<"Ma khach hang";
cout.width(15);
cout<<"So luong";
cout<<"Thanh tien||\n";
cachoadon->hienhoadon();
cout< }
}

void hoadon::dochoadon()
{
ifstream is(tephoadon);
while(1)
{
char mahoadon[10];
is.getline(mahoadon,sizeof(mahoadon));
char mamathang[15];
is.getline(mamathang,sizeof(mamathang));
char makhachhang[15];
is.getline(makhachhang,sizeof(makhachhang));
int soluong;
long thanhtien;
is>>soluong>>thanhtien;
is.ignore();
if(is.gcount()==0) break;
else
cachoadon[sohoadon++] =new hoadon(mahoadon,mamathang,makhachhang,soluong,thanhtien);
}
}


void hoadon::ghihoadon()
{
ofstream os(tephoadon);
for(int i=0;i {
os<->mahoadon< os<->mamathang< os<->makhachhang< os<->soluong<->thanhtien< }
}


//***************DOC GHI DU LIEU***************

//*** doc du lieu ***
void docdl()
{
mathang::dochang();
khachhang::dockhach();
hoadon::dochoadon();
}

//*** ghi du lieu ***
void ghidl()
{
mathang::ghihang();
khachhang::ghikhach();
hoadon::ghihoadon();
}

/*******************Menu MAT HANG********************/
void menuMH()
{
int chon1;
while(1)
{
cout<<"||========================================||\n";
cout<<"|| MENU MAT HANG ||\n";
cout<<"||========================================||\n";
cout<<"||1. Liet ke cac mat hang ||\n";
cout<<"||2. Nhap them mat hang moi ||\n";
cout<<"||3. Tim mot mat hang trong danh sach ||\n";
cout<<"||4. Nhap them so luong cua mot mat hang ||\n";
cout<<"||5. Chinh sua thong tin mat hang ||\n";
cout<<"||6. Xoa mot mat hang trong danh sach ||\n";
cout<<"||0. Tro lai MENU truoc ||\n";
cout<<"||========================================||\n";
cout<<"\tMoi ban nhap vao luu chon: ";
cin>>chon1;
switch(chon1)
{
case 1:mathang::lietkehang();break;
case 2:mathang::themhang();break;
case 3:mathang::timhang();break;
case 4:mathang::nhaphang();break;
case 5:mathang::suahang();break;
case 6:mathang::xoahang();break;
case 0:ghidl();clrscr();return;
default:
cout<<"\n Lua chon sai-Moi ban chon lai";
}
}
}
/*******************Menu KHACH HANG*******************/
void menuKH()
{
int chon2;
while(1)
{
cout<<"||========================================||\n";
cout<<"|| MENU KHACH HANG ||\n";
cout<<"||========================================||\n";
cout<<"||1. Liet ke cac khach hang ||\n";
cout<<"||2. Nhap them khach hang ||\n";
cout<<"||3. Tim mot khach hang trong danh sach ||\n";
cout<<"||4. Sua mot khach hang trong danh sach ||\n";
cout<<"||5. Xoa mot khach hang trong danh sach ||\n";
cout<<"||0. Tro lai MENU truoc ||\n";
cout<<"||========================================||\n";
cout<<"\tMoi ban nhap vao luu chon: ";
cin>>chon2;

switch(chon2)
{
case 1:khachhang::lietkekhach();break;
case 2:khachhang::themkhach();break;
case 3:khachhang::timkhach();break;
case 4:khachhang::suakhach();break;
case 5:khachhang::xoakhach();break;
case 0:ghidl();clrscr();return;
default:
cout<<"\n Lua chon sai-Moi ban chon lai\n";
}
}
}
/*****************Menu HOA DON******************/
void menuHD()
{
int chon3;
while(1)
{
cout<<"||========================================||\n";
cout<<"|| MENU HOA DON ||\n";
cout<<"||========================================||\n";
cout<<"||1. Hien thi cac hoa don mua hang ||\n";
cout<<"||2. laptop hoa don mua hang ||\n";
cout<<"||3. Sua mot hoa don trong danh sach ||\n";
cout<<"||4. Tim mot hoa don trong danh sach ||\n";
cout<<"||5. Xoa mot hoa don khoi danh sach ||\n";
cout<<"||0. Tro lai MENU truoc ||\n";
cout<<"||========================================||\n";
cout<<" Moi ban nhap vao luu chon: ";
cin>>chon3;
switch(chon3)
{
case 1:hoadon::danhsachcachoadon();break;
case 2:hoadon::laphoadon();break;
case 3:hoadon::suahoadon();break;
case 4:hoadon::timhoadon();break;
case 5:hoadon::xoahoadon();break;
case 0:ghidl();clrscr();return;
default:
cout<<"\n Lua chon sai-Moi ban chon lai\n";
}
}
}
/*******************HAM MAIN******************/
void main()
{
docdl();
int chon;
while(1)
{
cout<<"||========================================||\n";
cout<<"|| LUA CHON CAC CHUC NANG ||\n";
cout<<"||========================================||\n";
cout<<"||1. Cac chuc nang ve xu ly MAT HANG ||\n";
cout<<"||2. Cac chuc nang ve xu ly KHACH HANG ||\n";
cout<<"||3. Cac chuc nang ve xu ly HOA DON ||\n";
cout<<"||0. Thoat ||\n";
cout<<"||========================================||\n";
cout<<" Moi ban nhap vao lua chon: ";

cin>>chon;
clrscr();

switch(chon)
{
case 1: menuMH();break;

case 2: menuKH();break;

case 3: menuHD();break;

case 0: ghidl();exit(0);
default:
cout<<"\n\tLua chon sai-Moi ban chon lai\n";

}
}
}

/************************************************/

Các anh giải thích cho em về mấy cái static trong class.Tại sao khi khai báo biến static ở trong phần private lại phải khai báo thêm ở ngoài nữa.Các anh chỉ cho em sự khác nhau khi dùng static và khi không dùng static.Nếu như bài này em không dùng static void nữa mà dùng void không thôi thì đoạn code trên phải sửa như nào để chạy được.


Thanks các anh rất nhiều ^^!