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

Interview Questions and Answers - Order By Rating

Q31. What is "this" keyword used for ?

Ans. Used to represent an instance of the class in which it appears.

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Q32. What is "Import" used for ?

Core Java

Ans. Enables the programmer to abbreviate the names of classes defined in a package.

Sample Code for import

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Q33. What is a Static import ?

Core Java

Ans. By static import , we can access the static members of a class directly without prefixing it with the class name.

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Advanced level question usually asked to senior developers , leads and architects.

Q34. How does volatile affect code optimization by compiler?

Core Java

Ans. Volatile is an instruction that the variables can be accessed by multiple threads and hence shouldn't be cached. As volatile variables are never cached and hence their retrieval cannot be optimized.

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Q35. Can we use "this" within static method ? Why ?

Core Java

Ans. No. Even though "this" would mean a reference to current object id the method gets called using object reference but "this" would mean an ambiguity if the same static method gets called using Class name.

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Rarely asked as default methods have been introduced with Java 8.

Q36. Can we have a default method definition in the interface without specifying the keyword "default" ?

Core Java

Ans. No. Compiler complains that its an abstract method and hence shouldn't have the body.

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Q37. Why can't we use this in static context ?

Core Java

Ans. Static methods can be called using instance references wherein this would have made sense but static method can also be called using Class name wherein this would mean nothing and hence forbidden.

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Q38. In majority of the situations it won't make much sense whether you append this with the instance method call.Can you tell a situation wherein this keyword would make sense in a instance method ?

Core Java

Ans. Within instance method of the parent class that has other multiple methods that have been overridden by the derived classes.

In such case a simple method call from the common method will always be made to the method definition in the parent class. But If we use this.methodCall , this will be polymorphic and will be made to the respective derived object overriding method.

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Q39. Which of the following is not the use of this keyword ?

a. Passing itself to another method
b. To call the static method
c. Referring to the instance variable when local variable has the same name
d. Calling another constructor in constructor chaining

Ans. To call the static method

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Q40. Which of the following is not true for final variables ?

a. They cannot be changed after initialization
b. They can be initialized within static method
c. They can be declared and initialized together at the same place
d. They can be initialized within constructor

Ans. They can be initialized within static method

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Q41. Which of the following is false for final ?

a. Final methods cannot be overriden
b. Final methods cannot be overloaded
c. Final classes cannot be subclassed
d. Final class cannot be abstract

Ans. Final methods cannot be overloaded

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Q42. Which of the following combination of keywords is illegal in Java ?

a. static and transient
b. transient and final
c. static and synchronized
d. abstract and final

Core Java

Ans. abstract and final

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Q43. Which of the following keyword is not permitted for outer class ?

a. public
b. abstract
c. final
d. protected

Ans. protected

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Q44. Can we add more elements to an array list that has been marked as final ?

Ans. Yes, the array list can hold more elements. Final only puts the restriction that the array list reference cannot hold any other array list.

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Q45. Why can't we declare a class abstract as well as final ?

Core Java

Ans. Abstract means that the class is only meant to be subclassed whereas final means that it cannot be subclassed so both concepts - abstract and final are actually mutually exclusive and hence not permitted together.

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Q46. What will be the output of following code ?

public class BuggyBread {

   private int x;

   private BuggyBread(int x){
      x = x;
   };

   public static void main(String[] args){
      BuggyBread buggybread = new BuggyBread(5);
      System.out.println(buggybread.x);
   }
}

Core Java

a. compilation error

b. undefined

c. 0

d. 5

Ans.c. 0

Q47. The use of volatile keyword facilitates ..

Core Java

a. Making Use of Cache for better Performance

b. Avoiding use of Cache

c. Making use of Backward as well as Forward Cache

d. Keeping only one copy of variable in Cache