参考答案

正确答案：如果命令行上有一个文件名就读取该文件；否则只需在ManyVehicles类的main方法中创建一些手工编码的示例。下面给出了决定如何创建Vehicles以及创建这些示例的代码段：if(args．1ength==0){//There is no file name on the command lineso//make up some vehicles with hard codingvehicles[0]=new Vehicle("Ford""Mustang"2"red")；vehicles[1]=new Vehicle("BMW""328i"4"silver")；vehicles[2]=new Vehicle("Chrysler""PT Cruiser"4"goid")；System．out．println ("There are"+Vehicle．vehicleCount+"vehicles．")；System．out．println("Make of vehicles[0]："+vehicles[0]．getMake())；System．out．println("Model of vehicles[1](328i)："+vehicles[1]．getModel())；System?out．println("Color of vehicles[2](gold)："+vehicles[2]．getColor())；System．out．println("Max occupants of vehicles[0]："+vehicles[0]．getMaxOccupants())；}else{ //There is a file name on the command lineso//read from a file using Scanner．Scanner sc=null；try{SC=new Scanner(new Fi]e(args[0]))；}catch(Exception e){System．out．println(e.getMessage())；}int index=0；while(sc．hasNext()){ //read 1ine in filevehicle =sc．next()；c010r =sc．next()；mske =sc．next()；model =sc．next()；maxOccupants=sc．nextInt()；if(vehicle．equals("Vehicle")){vehicles[index]=new Vehicle(makemodelmaxOccupantscolor)；}else if(vehicle．equals("Bus")){vehicles[index]：new Bus(makemodelmaxOccupantscolorsc．next())；}else if(vehicle．equals("Skateboard")){vehicles[index]=new Vehicle(makemodelmaxOccupantscolor)；}else{System．out．println("Unrecognized vehicle type："+vehiCle)；System．exit(1)；}System．out．printin("Created"+vehicles[index]．getModel())；index++；} //while} //else注意：还必须在源代码文件的开头添加下面这些import语句甚至要使它们位于public class ManyVehicles{…的声明上面：import java．util．Scanner； //for access to the Scanner classimport java．io．*； //for access to file I/O
如果命令行上有一个文件名,就读取该文件；否则,只需在ManyVehicles类的main方法中创建一些手工编码的示例。下面给出了决定如何创建Vehicles以及创建这些示例的代码段：if(args．1ength==0){//Thereisnofilenameonthecommandline,so//makeupsomevehicleswithhardcodingvehicles[0]=newVehicle("Ford","Mustang",2,"red")；vehicles[1]=newVehicle("BMW","328i",4,"silver")；vehicles[2]=newVehicle("Chrysler","PTCruiser",4,"goid")；System．out．println("Thereare"+Vehicle．vehicleCount+"vehicles．")；System．out．println("Makeofvehicles[0]："+vehicles[0]．getMake())；System．out．println("Modelofvehicles[1](328i)："+vehicles[1]．getModel())；System?out．println("Colorofvehicles[2](gold)："+vehicles[2]．getColor())；System．out．println("Maxoccupantsofvehicles[0]："+vehicles[0]．getMaxOccupants())；}else{//Thereisafilenameonthecommandline,so//readfromafileusingScanner．Scannersc=null；try{SC=newScanner(newFi]e(args[0]))；}catch(Exceptione){System．out．println(e.getMessage())；}intindex=0；while(sc．hasNext()){//read1ineinfilevehicle=sc．next()；c010r=sc．next()；mske=sc．next()；model=sc．next()；maxOccupants=sc．nextInt()；if(vehicle．equals("Vehicle")){vehicles[index]=newVehicle(make,model,maxOccupants,color)；}elseif(vehicle．equals("Bus")){vehicles[index]：newBus(make,model,maxOccupants,color,sc．next())；}elseif(vehicle．equals("Skateboard")){vehicles[index]=newVehicle(make,model,maxOccupants,color)；}else{System．out．println("Unrecognizedvehicletype："+vehiCle)；System．exit(1)；}System．out．printin("Created"+vehicles[index]．getModel())；index++；}//while}//else注意：还必须在源代码文件的开头添加下面这些import语句,甚至要使它们位于publicclassManyVehicles{…的声明上面：importjava．util．Scanner；//foraccesstotheScannerclassimportjava．io．*；//foraccesstofileI/O