Inheritance - Absolute Java - page 469

instanceof and getClass() ★

Both the instanceof operator and the getClass() method can be used to check
the class of an object. The instanceof operator simply tests an object for type. The
getClass() method, used in a test with == or != , tests if two objects were created with
the same class. The details follow.

THE instanceof OPERATOR
The instanceof operator checks if an object is of the type given as its second argument.
The syntax is

Object instanceof Class_Name

which returns true if Object is of type Class_Name ; otherwise it returns false . So, the
following will return true if otherObject is of type Employee :

(otherObject instanceof Employee)

Note that this means it returns true if otherObject is of the type of any descendent
class of Employee , because in that case otherObject is also of type Employee .

THE getClass() METHOD

Every object inherits the method getClass() from the class Object . The method
getClass() is marked final in the class Object , so it cannot be overridden. For any
object of any class,

object.getClass()

returns a representation of the class that was used with new to create object . Any two
such representations can be compared with == or != to determine whether or not they
represent the same class. Thus,

if (object1.getClass() == object2.getClass())
System.out.println("Same class.");
else
System.out.println("Not the same class.");

will output Same class if object1 and object2 were created with the same class when
they were created using new , and output Not same class otherwise.

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