Core Java - Interview Questions and Answers for 'Nullpointerexception' | Search Interview Question

Core Java - Interview Questions and Answers for 'Nullpointerexception' - 5 question(s) found - Order By Newest

Q1. When does an application throw NullPointerException ?

Core Java

Ans. When it tries to access an object element or method using reference which is actually null.

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Q2. Is it ok to use optional everywhere just to get over nullpointerexception ?

Core Java

Ans. Optional is to be used for arguments / atrributes which are indeed optional i.e the request should continue even if they aren't provided. It should not be used for mandatory attributes or arguments as we would like application to shout out ( with error message / exception trace ) to signify a problem.

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Q3. How can we protect an application from throwing a NullPointerException ?

Ans. By having Null Checks.

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Q4. Doesn't it make sense to necessarily initialize references to some object to avoid NullPointerExceptions ? Can this be done ?

Core Java

Ans. We can declare the reference as final to avoid reassignment but again we can always initialize the final reference to null. Even if there was any such facility available , it would have meant poor use of resources by assigning a new object in memory to each reference that's created. Many a times references are just meant to refer to other objects which already have a reference i.e sharing object by multiple references.

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Q5. Is it a bad practice to initialize object reference to Null ?

Core Java

Ans. never initialise local to null,yes it is bad pratice

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Q6. Which of the following is a valid way to avoid NullPointerException ?

Core Java

a. Avoid assigning null to the reference

b. Null Checks before accessing elements of an object

c. Both of the above

d. None of the above

Ans.b. Null Checks before accessing elements of an object

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