在java中使用泛型时的ClassCastException
我是java编程新手,正在学习泛型。我试图自己编写一些泛型程序,但在线程“main”java.lang.ClassCastException:[Ljava.lang.Object;无法转换为[Lcom.ashwin.model.Car; 我有一辆车辆等级:在java中使用泛型时的ClassCastException,java,generics,Java,Generics,我是java编程新手,正在学习泛型。我试图自己编写一些泛型程序,但在线程“main”java.lang.ClassCastException:[Ljava.lang.Object;无法转换为[Lcom.ashwin.model.Car; 我有一辆车辆等级: public class Vehicle { private int id; private String name; private String color; private int plateNo; //
public class Vehicle {
private int id;
private String name;
private String color;
private int plateNo;
//omitted getters and setters
}
我有一辆汽车等级扩展到汽车等级
public class Car extends Vehicle {
public Car(int id, String name, String color, int plateNo) {
super.setId(id);
super.setColor(color);
super.setPlateNo(plateNo);
}
}
我有CarDAOImpl.java课程:
public class CarDAOImpl implements VehicleDAO<Car> {
private static ParkingLot<Car> park=new ParkingLot<Car>(10);
@Override
public boolean insert(Car v) {
if(park.getSpace()==-1) {
return false;
}
else {
park.setSpace(park.getSpace()-1);
park.setVehicle(v);
return true;
}
}
@Override
public boolean delete(Car k) {
if(park.getSpace()==10) {
return false;
}
else {
boolean result=park.deleteVehicle(k);
return result;
}
}
@Override
public Car[] getAll() {
return park.getVehicle();
}
}
public class ParkingLot<T> {
private int space;
private T[] vehicle;
public ParkingLot() {
}
public ParkingLot(int sp) {
this.vehicle=(T[])new Object[sp];
this.space=sp;
}
public int getSpace() {
return space;
}
public void setSpace(int space) {
this.space = space;
}
public T[] getVehicle() {
return vehicle;
}
public void setVehicle(T vehicle) {
this.vehicle[space]=vehicle;
}
public <T extends Vehicle> boolean deleteVehicle(T v) {
for(int i=0;i<vehicle.length;i++) {
if(((Vehicle) vehicle[i]).getId()==v.getId()) {
vehicle[i]=null;
return true;
}
}
return false;
}
}
例外情况是:
Exception in thread "main" java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Lcom.ashwin.model.Car;
您需要更新构造函数以将类对象包含为参数:
public ParkingLot(Class<T> clazz, int sp) {
this.vehicle= (T[]) Array.newInstance(clazz, sp);
this.space=sp;
}
公共停车场(等级分类,内部sp){
this.vehicle=(T[])Array.newInstance(clazz,sp);
这个空间=sp;
}
您的变量声明应该如下所示:
private static ParkingLot<Car> park = new ParkingLot<>(Car.class, 10);
私人静态停车场停车场=新停车场(汽车等级,10);
检查编译器给你的警告:数组和泛型不能很好地混合。相反,坚持使用集合(如列表
),它会起作用。cast(t[])
是一个不安全的类型,因此无法保证类型安全和(扰流板警报)如果没有一些重要的技巧,你就无法摆脱它。只要不要混合数组和泛型,你会过得更好。我同意使用List
的建议,但是你不能简单地在抛出错误的函数上返回Vehicle[]
?
public ParkingLot(Class<T> clazz, int sp) {
this.vehicle= (T[]) Array.newInstance(clazz, sp);
this.space=sp;
}
private static ParkingLot<Car> park = new ParkingLot<>(Car.class, 10);