填空题 [说明]
下面程序是为汽车市场编制的一个程序的一部分。其中automobile是基类。
[Java程序]
class MainJava
public static void main (String agr[]
car sedan=new car;
sedan.initialize (24, 20.0, 4);
System.out.println("The sedan can travel"
+ (1) +"miles./n");
System.out .println("The sedan has"
+ (2) +"doors./n");


class automobile
protected int miles_per_gallon; //汽车每加仑行驶公里数
(3) double fuel_capacity; //油箱容积
public void initialize (int in_mpg, int in_fuel)
miles_per_gallon=in_mpg;
fuel_capacity=in_fuel;

public int get_mpg() //提供一辆特定汽车每加仑公里数
return miles_per_gallon;

public double get_fuel() //提供油箱容积
return fuel_capacity;

public double travel_distance() //计算满油箱情况下的可行驶总公里数
return (4) ;


class car (5)
private int Total_doors;
public void initialize(int in_mpg, double in_fuel, int doors)
Total_doors=doors;
miles_per_gallon=in_mpg;
fuel_capacity=in_fuel;

public int doors()
return Total_doors;