java - 扩展类和实现接口(interface)之间的交互

Question

public class Main {

public static class ClassBase {

    public void test() {
        System.out.println("1");
    }

}

public static interface Interface {

    default void test() {
        System.out.println("2");
    }

}

public static class MyClass extends ClassBase implements Interface {

}

public static void main(String[] args) {
    new MyClass().test();
}

}

在这个例子中，它总是打印 1。要打印 2，我必须覆盖 MyClass 中的 test 并返回 Interface.super.test()。

有没有办法让 Interface::test 方法覆盖 ClassBase::test 方法，而无需手动覆盖 MyClass 中的方法？(在示例中打印 2)

Answer 1

If any class in the hierarchy has a method with same signature, then default methods become irrelevant. A default method cannot override a method from java.lang.Object. The reasoning is very simple, it’s because Object is the base class for all the java classes. So even if we have Object class methods defined as default methods in interfaces, it will be useless because Object class method will always be used. That’s why to avoid confusion, we can’t have default methods that are overriding Object class methods.

结论:默认方法不能覆盖实例方法。