Class instanceof isInstance

class Base{}
class Derived extends Base{}
class HiDerived extends Derived{}
/**
 * 2018/09/11 <<thinking in java>> RTTI
 * instanceof Class isInstance 等价性
 * @author zz2108828
 */
public class Test{
	static void test (Object x) {
		System.out.println("-----------Current type: " + x.getClass());
		System.out.println("x instance of Base " + (x instanceof Base));
		System.out.println("x instance of Derived " + (x instanceof Derived));
		System.out.println("x instance of HiDerived " + (x instanceof HiDerived));
		System.out.println("Base.isInstance(x) " + Base.class.isInstance(x));
		System.out.println("Derived.isInstance(x) " + Derived.class.isInstance(x));
		System.out.println("HiDerived.isInstance(x) " + HiDerived.class.isInstance(x));
		System.out.println("x.getClass() == Base.class "+ (x.getClass() == Base.class));
		System.out.println("x.getClass() == Derived.class " + (x.getClass() == Derived.class));
		System.out.println("x.getClass().equals(Base.class) " + x.getClass().equals(Base.class));
		System.out.println("x.getClass().equals(Derived.class) "+x.getClass().equals(Derived.class));
		System.out.println("x.getClass().isAssignableFrom(Base.class) " +(x.getClass().isAssignableFrom(Base.class)));
		System.out.println("x.getClass().isAssignableFrom(Derived.class) " +(x.getClass().isAssignableFrom(Derived.class)));
		System.out.println("x.getClass().isAssignableFrom(HiDerived.class) " +(x.getClass().isAssignableFrom(HiDerived.class)));
	}
	public static void main(String[] args) {
		test(new Base());
		test(new Derived());
	}
}

-----------Current type: class Base
x instance of Base true
x instance of Derived false
x instance of HiDerived false
Base.isInstance(x) true
Derived.isInstance(x) false
HiDerived.isInstance(x) false
x.getClass() == Base.class true
x.getClass() == Derived.class false
x.getClass().equals(Base.class) true
x.getClass().equals(Derived.class) false
x.getClass().isAssignableFrom(Base.class) true
x.getClass().isAssignableFrom(Derived.class) true
x.getClass().isAssignableFrom(HiDerived.class) true
-----------Current type: class Derived
x instance of Base true
x instance of Derived true
x instance of HiDerived false
Base.isInstance(x) true
Derived.isInstance(x) true
HiDerived.isInstance(x) false
x.getClass() == Base.class false
x.getClass() == Derived.class true
x.getClass().equals(Base.class) false
x.getClass().equals(Derived.class) true
x.getClass().isAssignableFrom(Base.class) false
x.getClass().isAssignableFrom(Derived.class) true
x.getClass().isAssignableFrom(HiDerived.class) true

转载于:https://www.cnblogs.com/--zz/p/9630415.html