单选题11. abstract class Vehicle { public int speed（） { return 0； } }  12. class Car extends Vehicle { public int speed（） { return 60； } }  13. class RaceCar extends Car { public int speed（） { return 150； }}  ......  21. RaceCar racer = new RaceCar（）；  22. C

能将程序补充完整的选项是______。 class Person{ private int a； phblic int change(int m){return m；} } public class Teacher extends Person{ public int b； public static void main(String arg[ ]){ Person p=new Person( )； Teacher t=new Teacher( )； int i; ______； } }

A．i=m

B．i=b

C．i=p.a

D．i=p.change(50)

A.Foo { public int bar() { return 1; }

B.new Foo { public int bar() { return 1; }

C.new Foo() { public int bar() { return 1; }

D.new class Foo { public int bar() { return 1; }

class A

{public int getNumber(int a){return a+1;}}

class B extends A

{public int getNumber(int a, char c){return a+2;}public static void main(String[] args){B b=new B();System.out.println(b.getNumber(0));}}

what is the result?()

A.compilation succeeds and 1 is printed

B.compilation succeeds and 2 is printed

C.compilation succeeds and 3 is printed

D.An error at this program cause compilation to fail

使用VC6打开考生文件夹下的工程test17_1，此工程包含一个源程序文件test17_1．唧，但该程序运行有问题，请改正程序中的错误，使程序的输出结果如下：

Vehicle message

Car message

Vehicle message

源程序文件test17_1.cpp 清单如下:

include ＜iostream.h＞

class vehicle

{

int wheels;

float weight;

public:

/***************** found *****************/

void message(void){ cout＜＜"Vehicle message\n";}

};

class car:public vehicle

{

int passenger_load;

public:

/***************** found *****************/

void message (void){cout＞＞"Car message\n";}

};

class truck:public vehicle

{

int passenger_load;

float payload;

public:

int passengers(void){return passenger_load;}

};

void main()

{

vehicle * unicycle;

unicycle=new vehicle;

/***************** found *****************/

unicycle.message()

delete unicycle;

unicycle=new car;

unicycle-＞message();

delete unicycle;

unicycle=new truck;

unicycle-＞message();

delete unicycle;

}

阅读以下说明和Java代码，填充程序中的空缺，将解答填入答题纸的对应栏内。

【说明】

某应急交通控制系统(TraficControIS，stem)在红灯时控制各类车辆(Vehicle)的通

行，其类图如图6-1所示，在紧急状态下应急车辆在红灯时可通行，其余车辆按正常规

则通行。

下面的Java代码实现以上设计，请完善其中的空缺。

【Java代码】

abstract class Vehicle

public Vehicle () { }

abstract void run

};

interface Emergency {

(1) ;

(2) ；

}

class Car extends Vehicle {

public Car () { }

void run () { /*代码略*/ }

};

class Truck extends Vehicle {

public Truck () { }

void run () { /*代码略*/ }

class PoliceCar (3)

boolean isEmergency = false;

public PoliceCar () { }

public PoliceCar(boolean b) { this . isEmergency =b; }

public boolean isEmergent () { return (4); }

public void runRedLight () { /*代码略*/ }

}

/*类Ambulance. FireEngine实现代码略*/

public class TraficControISystem {／。交通控制类。／

private Vehicle[ ]V=new Vehiele [24];

int numVehicles;

public void control() {

for (int i=0; i<numVehicles; i++) {

if (v[i] instanceof Enu rgency&& ((Emergency)V [i])

isEmergent()) {

( 5 ) . runRedLigh&39;: ( ) ;

}else

(6).run( )

}

}

void add (Vehicle vehicle) { v[numVehicles++]=vehicle;）／*添加车辆*／

void shutDown()（／*代码略*/}

public static void main (Stri.ng [ ] args) {

TraficControlSystem tcs = new TraficControlSystem() ;

tcs . add (new Car (） ;

tcs .add (new PoliceCar () ;

tcs .add (new Ambulance () ;

tcs . add (new Ambulance (true》 ;

tcs . add (new FireEngine ( true》 ;

tcs . add (new Truck () ;

tcs . add (new FireEngine ( ) ;

tcs . control () ;

tcs . shutDown () ;

}

}

能将程序补充完整的选项是( )。class Person{ private int a; public int change(int m){ return m; }}public class Teacher extends Person{ public int b; public static void main(String arg[]) { Person p = new Person(); Teacher t = new Teacher(); int i; ______ }} B.

A．i=m

B．i=b

C． i=p.a

D．i=p. change(50)