package exercise;
public interface Shape{
final double pi=3.14159;
double area(double r, double a, double b, double c);
double perimeter(double a, double b, double c, double r);
}
public class Rectangle implements Shape{
public double area(double r, double a, double b, double c) {
double area=a*b;
return area;
}
public double perimeter(double a, double b, double c, double r) {
double perimeter=a*2+b*2;
return perimeter;
}
}
public class Circle implements Shape{
public double area(double r, double a, double b, double c) {
double area=pi*r*r;
return area;
}
public double perimeter(double a, double b, double c, double r) {
double perimeter=2*pi*r;
return perimeter;
}
}
public class Triangle implements Shape{
public double area(double r, double a, double b, double c) {
double s=(a+b+c)/2;
double area=Math.sqrt(s*(s-a)*(s-b)*(s-c));
return area;
}
public double perimeter(double a, double b, double c, double r) {
double perimeter=a+b+c;
return perimeter;
}
}
将public 的class提到一个新的文件里边
或者 public修饰符去掉（不报错）
（一个文件只能有一个public的类）
假设你这个文件的文件名是Shape.java, 那么只保留 public class Shape 是public修饰，其他的public都去掉即可。