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

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Q1351. Have you worked on creating any cron job ?

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Q1352. Have you used any framework to capture command line arguments or options ?

Core Java

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Q1353. How would you choose your favorite company name for e.g. three companies are given in radio buttons Infosys, TCS and Aricent. Do You need to loop trough all radio buttons and select your favorite company or can just get the selected value.

Javascript

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Q1354. 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);

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Q1355. 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

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Q1356. What are the different types of methods in Java ?

Core Java

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

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Q1357. 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.

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Q1358. Design a class that find all files with SSN.

Core Java

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Q1359. Describe inheritance and polymorphism and their importance for OOP.

Core Java

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Q1360. 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);

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Q1361. Why do we need to close the Scanner ?

Core Java

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

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Q1362. 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.

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Q1363. 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.

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Q1364. Write a program that identifies numbers in a list that are palindrome and perfect square ?

Core Java

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Q1365. 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]

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Q1366. Explain Java collections

Core Java

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

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Q1367. 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;
   }

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Q1368. 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.

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Q1369. 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.

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Q1370. 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.

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Q1371. Find Intersection/union between two arrays.

Core Java

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Q1372. Find unique values between two arrays using single for loop ?

Core Java

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Q1373. Make "I Know Java" as "I Java Know" without using any inbuilt functions.

Core Java

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Q1374. Find out the max and min number from given array

Core Java

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Q1375. 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

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Q1376. 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.

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Q1377. Which of the Core Java functions / packages / concept do you believe have become irrelevant in today's market ?

Core Java

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Q1378. What is the difference between subscribe and blockingSubscribe method ?

RxJava

Ans. blockingSubscribe will block the current thread and wait till the chain completes

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Q1379. Difference between concatMap and flatMap ?

RxJava

Ans. Flatmap converts stream(s) into a single streams without maintaining a order where as concatmap does the same along with maintaining the order

flatmap example -[[1,2,3],[4,5,6],[7,8,9]] -> [1,4,7,2,5,8,3,6,9]

concatmap example -[[1,2,3],[4,5,6],[7,8,9]] -> [1,2,3,4,5,6,7,8,9]

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Q1380. What are the drawbacks of Reactive extensions ?

ReactiveX

Ans. Reactive extensions have a steep learning curve which makes it confusing for beginner and intermediate developers.

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