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

Interview Questions and Answers - Order By Newest

Q151. Difference between Encapsulation and Data Hiding ?

Ans. Data Hiding is a broader concept. Encapsulation is a OOP's centri concept which is a way of data hiding in OOP's.

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Q152. What is the use of HashCode in objects ?

Core Java

Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc.

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Q153. What will be the output of the following code ?

String s1 = "Buggy Bread";
String s2 = "Buggy Bread";
if(s1 == s2)
System.out.println("equal 1");
String n1 = new String("Buggy Bread");
String n2 = new String("Buggy Bread");
if(n1 == n2)
System.out.println("equal 2");

Core Java

Ans. equal 1

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Q154. Difference between PATH and CLASSPATH ?

Operating System

Ans. PATH is the variable that holds the directories for the OS to look for executables. CLASSPATH is the variable that holds the directories for JVM to look for .class files ( Byte Code ).

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Q155. Which markup languages can be used in restful web services ?

Rest

Ans. XML and JSON ( Javascript Object Notation ).

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Q156. Difference between Inner and Outer Join ?

Database

Ans. Inner join is the intersection of two tables on a particular columns whereas Outer Join is the Union of two tables.

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Q157. What is a Cursor ?

Database

Ans. It's a facility that allows traversal over the records pulled from a table or combination of tables. Its like iterator in Java.

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Q158. Which of the following syntax are correct ?a. LinkedList<Integer> l=new LinkedList<int>();b. List<Integer> l=new LinkedList<int>();c. LinkedList<Integer> l=new LinkedList<Integer>();d. List<Integer> l = new LinkedList<Integer>();

Core Java

Ans. All are correct.

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Q159. Can we have null keys in TreeMap ?

Core Java

Ans. No, results in exception.

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Q160. What are the different types of inheritance in Hibernate ?

Hibernate

Ans. Table Per Class , Table per Sub Class , Table per Concrete Class

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Q161. How to do Eager loading in Hibernate ?

Hibernate

Ans. Using

lazy = false in hibernate config file

or

@Basic(fetch=FetchType.EAGER) at the mapping

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Q162. What is the difference between int[] x; and int x[]; ?

Core Java

Ans. No Difference. Both are the acceptable ways to declare an array.

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Q163. How can we protect an application from throwing a NullPointerException ?

Ans. By having Null Checks.

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Q164. Why is a constant defined as a static final in Java?

Core Java

Ans. Final makes sure that the value doesn't change after initialization and static makes sure that there is only one copy that can be shared across objects.

Making it non static will unnecessarily create a different copy per object wherein the same value will kept for all copies ( as its final and cannot be changed ).

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Q165. What is Criteria in Hibernate ?

Hibernate

Ans. Criteria is a simplified API for retrieving entities by composing Criterion objects.

For example - session.createCriteria(Employee.class).add( Restrictions.like("name", "A%") ).list();

will return all employee objects having name starting with A.

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Q166. What is Jenkins ?

Jenkins

Ans. It is a continuous integration tool written in Java.

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Q167. Which takes more memory - float or Float ?

Core Java

Ans. float is a native data type whereas Float is a class. A Float object will always take more memory than float variable as there are metadata overheads with the objects.

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Q168. Which of the collections allows null as the key ?

a. HashTable
b. HashMap
c. TreeMap
d. LinkedHashMap

Core Java

Ans. HashMap

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Q169. Difference between prefix and postfix increment operator ?

Ans. Prefix operator performs the increment and then assignment whereas its inverse for postfix operator.

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Q170. Have you ever had any conflict with the team member (like disagreement on some design decision ) and How you reacted to it ?

General

Ans. [Open Ended Answer]

This is a very sensitive question and should be dealt with caution. Just simply saying that you never had any disagreement will present you as dumb team member. Showing your self as too aggressive in such decisions will present you as a trouble maker. You should present a situation where you had an argument / disagreement but eventually you and your team mates mutually found a way out of it.

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Frequently asked in face to face interviews.

Q171. Write a program to print fibonacci series.

Core Java

Ans. int count = 15;
int[] fibonacci = new int[count];
fibonacci[0] = 0;
fibonacci[1] = 1;
for(int x=2; x < count; x++){
fibonacci[x] = fibonacci[x-1] + fibonacci[x-2];
}

for(int x=0; x< count; x++){
System.out.print(fibonacci[x] + " ");
}

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Must know at all levels. Among Top 10 frequently asked questions in Java. Very frequently asked to fresh graduates or less experienced professionals.

Q172. What is Inheritance ?

Core Java

Ans. Its a facility for code reuse and independent extension wherein a derived class inherits the properties of parent class.

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Q173. What is a Java Bean ? How is it different from other Java classes ?

Ans. A Java bean is a class which abides by following conventions:

Core of the object is member elements and not operations ( methods )

Member Elements can be accessed by getters (and setters if those properties are not read-only).

serializable.

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Q174. How is static and dynamic polymorphism achieved in Java ?

Core Java

Ans. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding.

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Q175. Write a program / method to input few numbers and then print the sum.

Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?&category=code&searchOption&keyword=946

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Very frequently asked to fresh graduates. Frequently asked in NSEiT and Accenture India

Q176. Write a program to Generate prime numbers till a given number

Core Java

Ans. public class Main {
public static void main(String args[]) {
int number = 2;
int count = 0;
long sum = 0;
int givenNumber = 1000;
while (count < givenNumber) {
if (isPrimeNumber(number)) {
sum = number;
count;
}
number;
}
System.out.println(sum);
}
private static boolean isPrimeNumber(int number) {
for (int i = 2; i <= number / 2; i) {
if (number % i == 0) {
return false;
}
}
return true;
}
}

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Q177. Write a program to calculate factorial of a number using recursion

Core Java

Ans.

public class Factorial {
   public static void main(String[] args){
      int x = 5;

      System.out.println(calculateFactorial(x));

   }

   private static int calculateFactorial(int x){
      if(x==1){
         return 1;
      }
      return x * calculateFactorial(x-1);
   }
}

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Q178. Write code for constructor overloading

Core Java

Ans. http://javasearch.buggybread.com/CodeSnippets/searchCodeSamples.php?&category=code&searchOption&keyword=965

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Q179. What is a Destructor ? Do we have Destructors in Java ?

Core Java

Ans. Destructor is used to de-allocate memory allocated by objects.

There are no destructors in Java. Alternatively, Java provides Automatic garbage collection i.e automatically releasing the un-referenced memory.

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Frequently asked.

Q180. What should a class do if its implementing an interface ?

Core Java

Ans. It should either implement all interface methods or declare unimplemented methods as abstract.

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