案例01

package test;
public class InterfaceExercise01 {
    public static void main(String[] args) {
        B b = new B();//ok
        System.out.println(b.a);  //23
        System.out.println(A.a);  //23
        System.out.println(B.a);  //23
    }
}
interface A {
    int a = 23; //等价 public static final int a = 23;
}
class B implements A {//正确
}