instanceof如何在接口上工作

Question

instanceof可用于测试对象是否是给定类的直接或下降实例.instanceof即使接口无法像类一样实例化,也可以与接口一起使用.任何人都可以解释一下instanceof有效

Answer 1

首先,我们可以存储instances的实现特定的类interface在interface reference variable这样的.

package com.test;

public class Test implements Testeable {

    public static void main(String[] args) {

        Testeable testeable = new Test();

        // OR

        Test test = new Test();

        if (testeable instanceof Testeable)
            System.out.println("instanceof succeeded");
        if (test instanceof Testeable)
            System.out.println("instanceof succeeded");
    }
}

interface Testeable {

}

即,任何实现特定接口的运行时实例都将通过instanceof测试

编辑

和输出

instanceof succeeded
instanceof succeeded

@RohitJain

您可以使用像这样的匿名内部类来创建接口实例

Runnable runnable = new Runnable() {

    public void run() {
        System.out.println("inside run");
    }
};

并且您使用这样的instanceof运算符测试实例是接口类型

System.out.println(runnable instanceof Runnable);

结果是"真的"

Answer 2

object instanceof object_interface会屈服true.

Answer 3

您instanceof对a reference进行了instance检查,并检查该instance特定reference指向的类型.

现在既然你可以创建一个引用interface,它指向一个实现的实例class(相同的概念,Super class reference指向subclass instance).所以,你可以instanceof检查它.

例如: -

public interface MyInterface {
}

class ImplClass implements MyInterface {

    public static void main(String[] args) {
        MyInterface obj = new ImplClass();

        System.out.println(obj instanceof ImplClass);   // Will print true.
    }
}

Answer 4

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