instanceof

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public interface  A  {}

/** *  * @author thinkpad * Description :父类,实现接口A */public class B implements A{}

/** *  * @author thinkpad * Description :子类,继承B */public class C extends B{}

public class InstanceTest {    @Testpublic void testBestPractice() {A ab = new B();        A ac = new C();         B bb = new B();        B bc = new C();         C cc = new C();          //..instanceof A        System.out.println("ab instanceof A = " + (ab instanceof A));//ab instanceof A = true        System.out.println("ac instanceof A = " + (ac instanceof A));//ac instanceof A = true        System.out.println("bb instanceof A = " + (bb instanceof A));//bb instanceof A = true        System.out.println("bc instanceof A = " + (bc instanceof A));//bc instanceof A = true        System.out.println("cc instanceof A = " + (cc instanceof A));//cc instanceof A = true        System.out.println("null instanceof A = " + (null instanceof A));//null instanceof A = false        System.out.println("-------------------------------------");//        //..instanceof B        System.out.println("ab instanceof B = " + (ab instanceof B));//ab instanceof B = true        System.out.println("ac instanceof B = " + (ac instanceof B));//ac instanceof B = true        System.out.println("bb instanceof B = " + (bb instanceof B));//bb instanceof B = true        System.out.println("bc instanceof B = " + (bc instanceof B));//bc instanceof B = true        System.out.println("cc instanceof B = " + (cc instanceof B));//cc instanceof B = true        System.out.println("null instanceof B = " + (null instanceof B));//null instanceof B = false        System.out.println("-------------------------------------");        //..instanceof C        System.out.println("ab instanceof C = " + (ab instanceof C));//ab instanceof C = false        System.out.println("ac instanceof C = " + (ac instanceof C));//ac instanceof C = true        System.out.println("bb instanceof C = " + (bb instanceof C));//bb instanceof C = false        System.out.println("bc instanceof C = " + (bc instanceof C));//bc instanceof C = true        System.out.println("cc instanceof C = " + (cc instanceof C));//cc instanceof C = true        System.out.println("null instanceof C = " + (null instanceof C));//null instanceof C = false        System.out.println("-------------------------------------");//    }}

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