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instance of operator

 
Mathew Lee
Ranch Hand
Posts: 238
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I was reading following question from link
http://www.jchq.net/certkey/0501certkey.htm
>>>instanceof tests against a class name and not against an object reference for a class
did not understand it clearly.


import java.awt.*;

public class InOfComp {
public static void main(String argv[]){
}//End of main

public void mymethod(Component c){
if( c instanceof Button){
Button bc = (Button) c;
bc.setLabel("Hello");
}
else
if (c instanceof Label){
Label lc = (Label) c;
lc.setText("Hello");
}
}//End of mymethod
}

I could not see output on console. How to run and see the output to understand instanceof concept relating to child etc classes.
 
Matthew Brown
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Well, the first reason there's no output is because your main method is completely empty.

Mathew - after over 200 posts here, you should have learned how to UseCodeTags by now.
 
Campbell Ritchie
Sheriff
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That code will work, but it is not object-oriented programming to test the type like that.
Do a search for "instanceof" and you will find other examples; I wrote about it on this forum about a week ago.
 
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