? ????? C ??? ?? ?? ??????? ????? ??? ??????? ??? ?? ?????. ??? ?? ?? ??? ?? ??, ?? Java ? C ??? ????, ? ??? ???? ????, C?? ?????? ?? ??? ???? ??? ?????.

Java ?? :

Java?? interface ????? ???? ???? ???? ???? implements ???? ?? ?????? ?????. ?? ??? ??? ????.

 <code class="java">interface Vehicle { int price(); } class Car implements Vehicle { private final int speed; public Car(int speed) { this.speed = speed; } @Override public int price() { return speed * 60; } } class Motorcycle implements Vehicle { private final int cc; public Motorcycle(int cc) { this.cc = cc; } @Override public int price() { return cc * 10; } } public class Main { public static void printVehiclePrice(Vehicle vehicle) { System.out.println("$" vehicle.price() ".00"); } public static void main(String[] args) { Car car = new Car(120); Motorcycle motorcycle = new Motorcycle(1000); printVehiclePrice(car); printVehiclePrice(motorcycle); } }</code>

C ?? ?? :

C ???? ?? ????? ????? ????. ??, ?? ? ?? ???? ???? ?????? ??? ????? ? ? ????.

?? ?? ??? ?? ?? ?? ?? ??? ?????.

 <code class="c">typedef enum { VEHICLE_CAR, VEHICLE_MOTORCYCLE } VehicleType;</code>

?? ?? ?? ?? ? ?? ???? ???? ?? ??? ?????.

 <code class="c">typedef struct { VehicleType type; int (*price)(void*); // 函數(shù)指針，指向價(jià)格計(jì)算函數(shù)} Vehicle;</code>

???? ??? ? ????? ??? ??????.

 <code class="c">typedef struct { VehicleType type; int speed; } Car; typedef struct { VehicleType type; int cc; } Motorcycle;</code>

?? ??? ? ?? ?? ?? :

 <code class="c">Car* car_init(int speed) { Car* car = malloc(sizeof(Car)); car->type = VEHICLE_CAR; car->speed = speed; return car; } int car_price(void* car) { return ((Car*)car)->speed * 60; } Motorcycle* motorcycle_init(int cc) { Motorcycle* motorcycle = malloc(sizeof(Motorcycle)); motorcycle->type = VEHICLE_MOTORCYCLE; motorcycle->cc = cc; return motorcycle; } int motorcycle_price(void* motorcycle) { return ((Motorcycle*)motorcycle)->cc * 10; }</code>

????? vehicle_price ??? ???? ?? ??? ?? ?? ?? ?? ??? ??????.

 <code class="c">int vehicle_price(Vehicle* vehicle) { switch (vehicle->type) { case VEHICLE_CAR: return car_price((Car*)vehicle); case VEHICLE_MOTORCYCLE: return motorcycle_price((Motorcycle*)vehicle); default: return 0; } } void print_vehicle_price(Vehicle* vehicle) { printf("$%d.00\n", vehicle_price(vehicle)); } int main() { Vehicle car_v = {VEHICLE_CAR, car_price}; ((Car*)&car_v)->speed = 120; // 強(qiáng)制類型轉(zhuǎn)換Vehicle motorcycle_v = {VEHICLE_MOTORCYCLE, motorcycle_price}; ((Motorcycle*)&motorcycle_v)->cc = 1000; // 強(qiáng)制類型轉(zhuǎn)換print_vehicle_price(&car_v); print_vehicle_price(&motorcycle_v); free((Car*)&car_v); free((Motorcycle*)&motorcycle_v); return 0; }</code>

? C ?? ??? ?????? ??? ???????? Java? ????? ?????? ? ??? ??? ? ?? ??? ?? ??? ?????. ? ???? ?? ?? ?? (AST)? ?? ??? ??? ??? ?? ? ??? ?? ?? ???? ???? ??????.

? ??? C?? ?? ??? ???? ????? ??? ?? ?????. ??? ??? PHP ??? ????? ?? ?? ??? ?????!