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What is a null reference reference variable? What happens if we try to print a null...

What is a null reference reference variable? What happens if we try to print a null reference variable? What happens if we try to call an instance method like toString() using a null reference variable?

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Answer #1 
null reference reference variable means having an object of value null

if we try to print a null reference variable then it prints null

if we try to call an instance method like toString() using a null reference variable then it throws java.lang.NullPointerException
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