21. What is use of wildcards?

1. 1. It is used for type argument of generic method

   
   
   

   2. It is used to access members of super class

   
   
   

   3. It is used to make code more readable

   
   
   

   4. It is used in cases when type being operated upon is not known

   
   
   

   5. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   The wildcard can be used in a variety of situations: as the type of a parameter, field, or local variable; sometimes as a return type (though it is better programming practice to be more specific). The wildcard is never used as a type argument for a generic method invocation, a generic class instance creation, or a supertype.

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22. Which of these keywords is used to upper bound a wildcard?
    

1. 1. extends

   
   
   

   2. implements

   
   
   

   3. bound

   
   
   

   4. stop

   
   
   

   5. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: A

   extends

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23. Which of these is an correct way making a list that is upper bounded by class Number?

1. 1. List(? UpperBounds Number)

   
   
   

   2. List(? extends Number)

   
   
   

   3. List

   
   
   

   4. List

   
   
   

   5. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   List

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24. Which of the following keywords are used for lower bounding a wild card?

1. 1. lower

   
   
   

   2. class

   
   
   

   3. extends

   
   
   

   4. super

   
   
   

   5. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: D

   A lower bounded wildcard is expressed using the wildcard character (‘?’), following by the super keyword, followed by its lower bound.

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