深入浅出：Java接口继承的演进之路

public interface Runner {
    default void run() {
        System.out.println("Running at default speed");
    }
    void stop(); // 仍是抽象方法
}

public interface Calculator {
    default int add(int a, int b) {
        return doCompute(a, b, '+');
    }
    private int doCompute(int x, int y, char op) {
        return op == '+' ? x + y : x - y;
    }
}

public sealed interface Shape permits Circle, Rectangle { /* ... */ }
public final class Circle implements Shape { /* ... */ }
public non-sealed class Rectangle implements Shape { /* ... */ }

// 定义密封接口
public sealed interface Vehicle permits Car, Bike {
    default void start() { System.out.println("启动"); }
    void stop();
}
// 具体实现
public final class Car implements Vehicle {
    @Override
    public void stop() { System.out.println("停车"); }
}
// 扩展开放
public non-sealed class Bike implements Vehicle {
    @Override
    public void stop() { System.out.println("停车（自行车）"); }
}

// 测试
public class Main {
    public static void main(String[] args) {
        Vehicle c = new Car();
        c.start(); c.stop();
    }
}