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Generics

 
Greenhorn
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what is difference between the following two methods ?

public void methodA(ArrayList<? extends String> list){}

public void methodB(ArrayList<? super String> list){}



and, How to invoke these methods ?
 
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Welcome to JR.

The answer is pretty simple. One accepts elements which are Strings and its subclass (String is final, there are no subclasses). The other takes Strings and its super classes (Object).

How to invoke these methods ?



What happened when you gave it a try ?
 
Ranch Hand
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Another thing to note that methodA is for read only, i.e. you can not do an add inside the methodA body, but methodB can have an add call inside its body:

 
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