java - 方法不重写或实现父类(super class)型中的方法 @override 编译错误

Question

我收到错误方法没有重写或实现父类(super class)型@Override 中的方法。我想在打印一辆车后打印“无法更改汽车的容量”。我需要重写 setCapacity 来打印其他部分。我相信代码大部分是正确的，只是不确定为什么它没有正确覆盖 setCapacity 方法。最终输出为:

New capacity = 1600
Vehicle Info:
capacity = 1600cc
make = Mazda
Cannot change capacity of a car
Vehicle Info:
capacity = 1200cc
make = Holden
type = sedan
model = Barina

我的代码是:

class Vehicle {  // base class

   public void setCapacity(int setCapacity) {
     this.capacity = setCapacity;
      System.out.println("New Capacity = " + setCapacity);
   }

   int capacity;
   String make;

   Vehicle(int theCapacity, String theMake) {
      capacity = theCapacity;
      make = theMake;
   }

   void print() {
      System.out.println("Vehicle Info:");
      System.out.println("  capacity = " + capacity + "cc" );
      System.out.println("  make = " + make );
   }
}

class Car extends Vehicle {
   public String type;
   public String model;

   public Car(int theCapacity, String theMake, String theType, String theModel) {
      super(theCapacity, theMake);
      type = theType;
      model = theModel;
   }

   @Override
   public void print() {
      super.print();
      System.out.println("  type = " + type);
      System.out.println("  model = " + model);

   }

     @Override
     public void setCapacity() {
       super.print();
       System.out.println("Cannot change capacity of a car");
     }       
 }

class Task3 {

   public static void main (String[]args){
      Car car1 = new Car (1200,"Holden","sedan","Barina" );
      Vehicle v1 = new Vehicle (1500,"Mazda");
      v1.setCapacity(1600);
      v1.print();
      car1.setCapacity(1600);
      car1.print();
   }
}

Answer 1

setCapacity() 的子方法和父方法签名不匹配。如果您想在子类中重写父类的方法，那么它必须具有相同的签名。

改变

public void setCapacity() { //... }

到

public void setCapacity(int setCapacity) { // ... }

在 Car 类中。

在您的代码中，您错过了参数setCapacity，因此编译器会提示。