public course Human //human stuffpublic class Developer expand Human //developer stuffWhy is Developer an circumstances of Human, but the course Developer is not assignable to Human?

Developer dev = brand-new Developer();System.out.println(dev instanceof Human); //trueSystem.out.println(Developer.class.isAssignableFrom(Human.class)); //falseBut in enhancement to this: person is assignable to Developer.

You are watching: A instance of a subclass is also an instance of its superclass.

System.out.println(Human.class.isAssignableFrom(Developer.class)); //trueIn typical English I would certainly say the a Developer thing is assignable indigenous a human being class, not the other way around.


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If you intend there is a role assignableTo, this is that you say but assignableFrom is reverse:

The java.lang.Class.isAssignableFrom() determines if the class or interface represented by this class object is one of two people the same as, or is a superclass or superinterface of, the class or user interface represented through the specified class parameter.

You deserve to learn much more enter this


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A Developer is-a Human, however not every human being is-a developer.

Inheritance imposes an is-a relationship on that children. This method that a kid can constantly be determined by their parent class, but a parental isn"t proven or demonstrated to be i can identify by their child.

In a nutshell, this is what isAssignableFrom is demonstrating; you"re wonder if a person is assignable native a Developer, i beg your pardon isn"t true. That type of assignment would certainly be Developer dev = new Human();, which just works the other method "round (i.e. Person human = brand-new Developer();).


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Human.class.isAssignableFrom(Developer.class)in English means: you can assign come a change of the person class things of the Developer class.


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In normal English I would certainly say, the a developer thing is assignable indigenous a person class, no the other way around.

And the trouble is your intake of the native "object" and also "class" here. It must be: a human variable is assignable indigenous a value of form Developer.

You assign a value to a variable from analyzing an expression.


You deserve to do:

Human human = brand-new Developer()But you can not do:

Developer developer = brand-new Human()In logical terms, every developer is a human being not every human is a developer.

If you had actually a class QaEngineer that would certainly inherit from human you won"t desire this to be allowed:

Developer developer = new QaDeveloper()or this:

Developer developer = (Human) new QaDeveloper()
from the documentation of the method

Determines if the course or interface represented by this class object is either the same as, or is a superclass or superinterface of, the course or user interface represented by the specified course parameter.<...>

So basicly the method returns, if the parameter class noted is the same course or interface, or a subclass or subinterface the the course it was invoked on.

Developer.class.isAssignableFrom(Human.class) // False, Developer is not a superclass that HumanHuman.class.isAssignableFrom(Developer.class) // True, human being is a superclass of Developer
Try come think it choose this:

Human.class.isAssignableFrom(Developer.class) //true; method you deserve to assign a developer object in reference of Human.

Developer.class.isAssignableFrom(Human.class) //false;means you deserve to not assign an item of Human course (parent) in the reference of Developer course (child). The core dominion is that: You deserve to assign an object of son to recommendation of parent, no the other method round.

Hope it helps.


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