前提條件:

class Father{}
class Child extends Father{}
Father father = new Father();
Child child = new Child();
Father child_father = new Child();

1.instanceof:

由這段程式碼可見,子類instanceof父類,判斷結果為true。

child instanceof Child//true
child instanceof Father//true

我們再看這段程式碼,父類instanceof子類,判斷結果為false

System.out.println(father instanceof Child);
 

那麼我們或許會有疑問,instanceof比較的究竟是引用還是例項,看下面這段程式碼就會有所瞭解,他的所有表現都跟其例項一樣

System.out.println(child_father instanceof Child);//ture
System.out.println(child_father instanceof Father);//true

由於null不是任何類的子類,所以結果false。注意instanceof後面的必須為一個Class,不能為null

null instanceof Object

2.isInstance 對於isInstance,我們可以看到如下所示

System.out.println(child.getClass().isInstance(child));//true
System.out.println(child.getClass().isInstance(father));//false
Child child2 = new Child();
System.out.println(child.getClass().isInstance(child2));//true

System.out.println(father.getClass().isInstance(child));//true
 

同樣,他比較的也是其例項

System.out.println(child_father.getClass().isInstance(child));//true
System.out.println(child_father.getClass().isInstance(father));//false

總結:(待補充)