英文:
Class is not abstract and does not override abstract method error... though it implements method
问题
我得到了不应该显示的错误消息。
首先，在创建接口之后，我将其方法复制到实现此接口的所有类中，但错误仍然显示。
目前代码如下：
interface Shape {
String getShapeName();
double getField();
}
class Circle implements Shape {
String name;
double r;
public Circle(String name, double r) {
this.name = name;
this.r = r;
}
@Override
public double getField() {
return Math.PI * Math.pow(r, 2);
}
@Override
public String getShapeName() {
return this.name;
}
}
class Square implements Shape {
String name;
double a;
public Square(String name, double a) {
this.name = name;
this.a = a;
}
@Override
public double getField() {
return Math.pow(a, 2);
}
@Override
public String getShapeName() {
return this.name;
}
}
class Triangle implements Shape {
String name;
double a;
double b;
double c;
public Triangle(String name, double a, double b, double c) {
this.name = name;
this.a = a;
this.b = b;
this.c = c;
}
@Override
public double getField() {
double p = (a + b + c) / 2;
return Math.sqrt(p * (p - a) * (p - b) * (p - c));
}
@Override
public String getShapeName() {
return this.name;
}
}
我不知道为什么会出现这种情况... 我看到这个问题已经被问了几次，但在大多数情况下，这是因为没有实现接口中的一些方法（或者方法名称输入错误），但这不适用于我的情况，因为接口方法已复制到所有三个类中...
英文:
I'm getting this error message which should not be showing.
First of all after creating interface I copied its method into all classes that implements this interface - but the error is still showing.
this currently looks like this:
interface Shape {
String getShapeName();
double getField();
}
class Circle implements Shape {
String name;
double r;
public Circle(String name, double r) {
this.name = name;
this.r = r;
}
@Override
public double getField(double r) {
return Math.PI * Math.pow(r, 2);
}
@Override
public String getShapeName() {
return this.name;
}
}
class Square implements Shape {
String name;
double a;
public Square(String name, double a) {
this.name = name;
this.a = a;
}
@Override
public double getField(double a) {
return Math.pow(a, 2);
}
@Override
public String getShapeName() {
return this.name;
}
}
class Triangle implements Shape {
String name;
double a;
double b;
double c;
public Triangle(String name, double a, double b, double c) {
this.name = name;
this.a = a;
this.b = b;
this.c = c;
}
@Override
public double getField(double a, double b, double c) {
double p = (a + b + c) / 2;
return Math.sqrt(p * (p - a) * (p - b) * (p - c));
}
@Override
public String getShapeName() {
return this.name;
}
}
And I have no idea why... I saw that this question was asked a few times but in most cases it was a result of not implementing some methods from interface (or a wrong typing method name which are not my cases as the interface methods were copied to all 3 classes...
答案1
得分: 1
interface Shape {
String getShapeName();
double getField();
}
然而，在你的子类中，你明确地声明你要覆盖：
@Override
public double getField(double r) {...}
double getField() 和 double getField(double r) 不是相同的。
覆盖与隐藏方法:
>子类中具有与超类中实例方法相同的签名（名称，加上参数的数量和类型）和返回类型的实例方法将覆盖超类的方法。
附注：@Override（它是@Retention(SOURCE)）注解在你的方法顶部，强制你覆盖相应的方法，否则你将无法编译你的文件。
英文:
You have:
interface Shape {
String getShapeName();
double getField();
}
however, you explicitly state in your sub-classes, that you override:
@Override
public double getField(double r) {...}
double getField() and double getField(double r) are not the same.
Overriding and Hiding Methods:
>An instance method in a subclass with the same signature (name, plus the number and the type of its parameters) and return type as an instance method in the superclass overrides the superclass's method.
Side-note: @Override (which is @Retention(SOURCE)) annotation on top of your method, enforces you to override corresponding method, otherwise you will not be able to compile your file.
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