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

Interview Questions and Answers - Order By Newest

Q991. Have you used any framework to capture command line arguments or options ?

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q992. Write code to get count of every 5 letter word in a string using lambda expression

Core Java

Ans. String str = "I had been saying that he had been there";

Map<String,Long> countWords = Arrays.asList(str.split(" ")).stream().filter(p->p.length() = 5).collect(Collectors.groupingBy(p->p,Collectors.counting()));

System.out.println(countWords);

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Collectors lambda filter coding java 8}

Q993. Can you write code so that we can keep track of Keys that have their values changed along with the number of times they were changed.

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q994. What are the different types of methods in Java ?

Core Java

Ans. Static Methods
Instance Methods
Accessor / Mutator or getter setters

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q995. Are getters setter / accessor mutator methods instance methods or static methods ? why ?

Core Java

Ans. They are usually instance methods. They are usually applied to DAOs / DTOs / POJO that are used to transport objects and used to access object elements. As they are tied to objects and are not common to all objects of a class, hence they are created as non static.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q996. Design a class that find all files with SSN.

Core Java

^{This question was recently asked at 'The Home Depot'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q997. Describe inheritance and polymorphism and their importance for OOP.

Core Java

^{This question was recently asked at 'The Home Depot'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q998. What is the difference between instantiation and initialization ?

Core Java

Ans. Instantiation is the process of reserving memory for the object

For ex -

List list = new ArrayList();

Initialization is the process of setting the default value for the object or default object construction.

List list = new ArrayList(set);

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q999. Why do we need to close the Scanner ?

Core Java

Ans. For releasing input stream reference (System.in), you should close scanner.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve scanner input output io}

Q1000. Can you explain filter and collectors in java 8 ?

Core Java

Ans. Filters are used to filter object in stream on certail criteria. And collector is used to collect outcome of the stream. Collector is a terminal operation.
List numbers = List.of(1,2,3,4,5,6,7);
List evenNumbers = numbers.stream().filter(n -> n%2==0).collect(Collectors.toList());
The above code will filter out odd numbers and return the list of even number.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve collector filter}

Q1001. Can you explain filter and collectors in java 8 ?

Core Java

Ans. Filters are used to filter object in stream on certain criteria.
Collector is used to collect outcome of the stream. Collector is a terminal operation.
List numbers = List.of(1,2,3,4,5,6,7);
List evenNumbers = numbers.stream().filter(n -> n%2==0).collect(Collectors.toList());
The above code will filter out odd numbers and return the list of even number.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve collectors filters java 8}

Q1002. Write a program that identifies numbers in a list that are palindrome and perfect square ?

Core Java

^{This question was recently asked at 'Spillman Technologies'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1003. Write a program to sort the Array of Strings

Core Java

Ans. String[] s = { "sort", "string", "array" };
Collections.sort(Arrays.asList(s));
System.out.println(Arrays.toString(s)); // [array, sort, string]

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1004. Explain Java collections

Core Java

Ans. Collection is a container which is used to store and manipulate the group of objects

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1005. Get all numbers from a collection that are both perfect square and palindome

Core Java

Ans. public static void main(String[] args){
      List<Integer> listOfIntegers = Arrays.asList(1,2,3,4,5,6,7,8,9,10,11);
      List<Integer> perfectAndPalindromeIntegers = new ArrayList<Integer>();

      for(Integer i: listOfIntegers){
         if(isPalindrome(i) && isPerfect(i)){
            perfectAndPalindromeIntegers.add(i);
         }
      }

      System.out.println(perfectAndPalindromeIntegers);
   }

   private static Boolean isPalindrome(Integer i){
      String str = String.valueOf(i);

      char[] charArray = str.toCharArray();

      int x = 0;
      int y = str.length()-1;

      while(x < y){
         if(charArray[x] != charArray[y]){
            return false;
         }
      }

      return true;
   }

   private static Boolean isPerfect(Integer i){
      for(int x=2;x<3;x++){
         if(x*x == i){
            return true;
         }
      }

      return false;
   }

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q1006. When to use List, Set and Map in Java

Core Java

Ans. I. If we want a Collection that does not store duplicate values, then we use a Set based collection.

II. If we want to frequently access elements operations based on an index value then we use a List based collection. E.g. ArrayList

III. If we want to maintain the insertion order of elements in a collection then we use a List based collection.

IV. For fast search operation based on a key, value pair, we use a HashMap based collection.

V. If we want to maintain the elements in a sorted order, then we use a TreeSet based collection.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1007. What is garbage collection ?

Core Java

Ans. The garbage collection is a facility wherein a program runs on the Java Virtual Machine which gets rid of objects, which are not being used by a Java application anymore. It is a form of automatic memory management and recollection.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 4 Companies}

Q1008. Can we change return type of Overridden method ?

Core Java

Ans. Yes, we can change return type of overridden method in child class but child's return type should be sub-type of parent's return type.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1009. Find Intersection/union between two arrays.

Core Java

^{This question was recently asked at 'Bristlecone,Amazon Lab126,Amazon,Microsoft,Facebook,NCR,Google'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve arrays code coding Asked in 7 Companies frequent}

Q1010. Find unique values between two arrays using single for loop ?

Core Java

^{This question was recently asked at 'Net connect'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve for loop control statements loop statement Asked in 1 Companies}

Q1011. Make "I Know Java" as "I Java Know" without using any inbuilt functions.

Core Java

^{This question was recently asked at 'iOPEX Technologies'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1012. Find out the max and min number from given array

Core Java

^{This question was recently asked at 'Expedia'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1013. Math.round method rounds the decimal to an integer by stripping off the decimal places. How can we use the same method to keep only 2 decimal places

For example -

Math.round(12.3456) will return 12. What should we do to get 12.34 without using any other class or method.

Core Java

Ans. We can multiply the value by 100 and then use Math.round on that and then divide the result by 100

For example -

(Math.round(12.3456 * 100)) / 100

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Math.round double}

Q1014. What is the difference between round and scale method of BigDecimal ?

Core Java

Ans. Round method would round it to integer places irrespective of if it's decimal places or not whereas scale would only round the decimal places.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve BigDecimal round scale}

Q1015. Which of the Core Java functions / packages / concept do you believe have become irrelevant in today's market ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve}

Q1016. Sort a List of Objects using comparable and comparator

Core Java

^{This question was recently asked at 'HCL Technologies'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1017. can we use null as keyword ?

Core Java

Ans. null is a literal similar to true and false in Java. These are not keywords because these are the values of something. As null is the value of a reference variable, true is the value of a boolean variable.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1018. what is directive ?

Core Java

Ans. A compiler directive is an instruction that tells the JVM how compilation should occur. A directive provides method-context precision in controlling the compilation process.

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1019. Which is the best collections for maintaining elements in an order ?

Core Java

^{This question was recently asked at 'Dell'.This question is still unanswered. Can you please provide an answer.}

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Q1020. What is Dynamic Binding ?

Core Java

Ans. Dynamic Binding happens at runtime. Method overriding is an example of Dynamic Binding

Help us improve. Please let us know the company, where you were asked this question :

_{Like Discuss Correct / Improve Asked in 1 Companies}

Search Interview Questions

Help us and Others Improve. Please let us know the questions asked in any of your previous interview.