Example description of alternative writing of instanceof

Reference material ：

instanceOf Alternative writing of method -- Have you ever seen ？

instanceof brief introduction :

    instanceof yes Java、php A binary operator of （ Operator ）, and ==,>,< It's the same thing . Because it's made up of letters , So too. Java Reserved keywords for . Its function is to determine whether the object on the left is an instance of the class on the right , return boolean Data of type . It can be used to judge whether the instance of the subclass in the inheritance is the implementation of the parent class . amount to c# Medium is The operator .java Medium instanceof Is to indicate by returning a Boolean value , Whether this object is an instance of this specific class or its subclass .

instanceof  yes Java Reserved keywords for , Its purpose is to test whether the object on its left is an instance of the class on its right , return  boolean  Data type of

matters needing attention :

    instanceof It can't be used to judge basic types , It can only be used to judge the reference type

instanceof Application scenarios of
      instanceof Keywords are often used to determine the type before casting , When the judgment is finished , Then follow up the corresponding conversion operation  

public B convert(A a) {
    if (a instanceof B) {
        return (B) a;
    }
    return null;
}
 instanceof Implementation principle of

    Use try catch Enforce , Conversion success , Then return to true, Instead, return to false

boolean rs;
if (obj == null) {
  rs= false;
} else {
  try {
      T temp = (T) obj; 
      rs= true;
  } catch (ClassCastException e) {
      rs = false;
  }
}
return rs; 

  example : 

      instanceof Use example of

 boolean result = object instanceof class
 Parameter description :
    Result： Boolean type .
     Object： Will options . Any object expression .
     class： Will options . Any defined object class .
 explain 
     When object  yes  class  An example of 
     be  instanceof  Operator return  true
     If  object  Not an instance of the specified class 
          or object  yes  null, Then return to  false.

instanceof Alternative writing use class One of the objects isInstance Method , As shown below  

if (classname.class.isInstance(othername)){
    // Business code 
}