Search Interview Questions | More than 3000 questions in repository. There are more than 900 unanswered questions. Click here and help us by providing the answer. Have a video suggestion. Click Correct / Improve and please let us know. |
|
| ||||
Interview Questions and Answers - Order By Newest | ||||
Frequently asked in all types of companies especially Indian Services companies. Frequently asked in CTS (Based on 2 feedback) | ||||
| ||||
Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc. The value received from hashcode() is used as bucket number for storing elements. This bucket number is the address of the element inside the set/map. when you do contains() then it will take the hashcode of the element, then look for the bucket where hashcode points to and if more than 1 element is found in the same bucket (multiple objects can have the same hashcode) then it uses the equals() method to evaluate if object are equal, and then decide if contain() is true or false, or decide if element could be added in the set or not. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   collections   hashcode   advanced  hashtable Asked in 33 Companies intermediate   frequent | ||||
Try 1 Question(s) Test | ||||
Very Frequently asked to fresh graduates and less experienced. Favorite question in Walk in drives. Frequently asked in Indian Services companies. | ||||
| ||||
Ans. Overloading - Similar Signature but different definition , like function overloading. Overriding - Overriding the Definition of base class in the derived class. | ||||
Sample Code for overloading Sample Code for overriding | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   oops   overloading   overriding   oops concepts   basic interview question   overloading vs overriding Asked in 86 Companies basic   frequent | ||||
Try 1 Question(s) Test | ||||
| ||||
Ans. Car Engine is an example of encapsulation and abstraction. You ignite the car using an interface called starter and least bothered about how the tire actually moves (This is abstraction). The engine encapsulates the complete process to itself only and doesn't allow you to start the other components like the radiator etc ( this is excapsulation ) | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  encapsulation  object oriented programming (oops)  oops concepts  abstraction  oops  oops features  java features Asked in 13 Companies | ||||
Very frequently asked across all types of companies. | ||||
| ||||
Ans. Hashtable is synchronized whereas HashMap is not.HashMap allows null values whereas Hashtable doesnt allow null values. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   collections   hashmap   map   hashtable   hashmap vs hashtable Asked in 14 Companies basic   frequent | ||||
Try 2 Question(s) Test | ||||
Advanced level question usually asked in High end product companies. Have been asked in Google and Amazon (Based on 1 Feedback) | ||||
| ||||
Ans. The Java runtime environment deletes objects when it determines that they are no longer being used. This process is known as garbage collection. The Java runtime environment supports a garbage collector that periodically frees the memory used by objects that are no longer needed. The Java garbage collector is a mark-sweep garbage collector that scans Java dynamic memory areas for objects, marking those that are referenced. After all possible paths to objects are investigated, those objects that are not marked (i.e. are not referenced) are known to be garbage and are collected. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   garbage collection   java memory management   advanced Asked in 21 Companies intermediate   frequent | ||||
Try 4 Question(s) Test | ||||
Advanced level question frequently asked in US based companies. Recently asked in EMC and Intuit. | ||||
| ||||
Ans. Simplest implementation we can have is a List wherein we can place ordered words and hence can perform Binary Search. Other implementation with better search performance is to use HashMap with key as first character of the word and value as a LinkedList. Further level up, we can have linked Hashmaps like , hashmap { a ( key ) -> hashmap (key-aa , value (hashmap(key-aaa,value) b ( key ) -> hashmap (key-ba , value (hashmap(key-baa,value) .................................................................................... z( key ) -> hashmap (key-za , value (hashmap(key-zaa,value) } upto n levels ( where n is the average size of the word in dictionary. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   collections   hashmap   binary search   search algorithm   advanced   architecture   data structure Asked in 6 Companies   frequent | ||||
Try 1 Question(s) Test | ||||
Frequently asked to fresh graduates and less experienced. | ||||
| ||||
Ans. 1. public is the access modifier that makes the method accessible from anywhere, static is the keyword that makes it accessible even without creating any object, void means it doesn't return anything , String args[] is the array of argument that the method receives. 2. If we use main without the string args , it will compile correctly as Java will treat it as just another method. It wont be the method "main" which Java looks for when it looks to execute the class and hence will throw Error: Main method not found in class , please define the main method as: public static void main(String[] args) 3. Main is not a keyword but a special string that Java looks for while initiating the main thread. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   main method Asked in 4 Companies basic   frequent | ||||
Try 1 Question(s) Test | ||||
Frequently asked to fresh graduates. | ||||
| ||||
Ans. ACID stands for Atomicity, Consistency, Isolation, Durability is a set of properties of database transactions. Atomicity means all or nothing. i.e parts of a transaction shouldn't commit if any one of them fails. Either the whole transaction should succeed or it should be complete rollback. Consistency means that any transaction should lead database from one stabe state to another. Isolation means that the execution of transaction results in a system state that would be obtained if transactions were executed serially. Durability means that when a transaction is committed it forms the permanent state of database. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  database  acid Asked in 7 Companies Intermediate | ||||
Try 1 Question(s) Test | ||||
Almost sure to be asked in every company using any Dependency Injection framework ( Spring, Guice etc ) | ||||
| ||||
Ans. It is a Design Pattern that facilitates loose coupling by sending the dependency information ( object references of dependent object ) while building the state of the object. Objects are designed in a manner where they receive instances of the objects from other pieces of code, instead of constructing them internally and hence provide better flexibility. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  design patterns   ioc ( Inversion of Control )  dependency injection Asked in 83 Companies intermediate   frequent | ||||
Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM. | ||||
| ||||
Ans. Volatile is a declaration that a variable can be accessed by multiple threads and hence shouldnt be cached. | ||||
Sample Code for volatile | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   oops   synchronization   volatile   java keywords Asked in 42 Companies intermediate   frequent | ||||
Try 1 Question(s) Test | ||||
Very frequently asked.Usually among first few questions. | ||||
| ||||
Ans. MVC is a Design Pattern that facilititates loose coupling by segregating responsibilities in a Web application 1. Controller receives the requests and handles overall control of the request 2. Model holds majority of the Business logic, and 3. View comprise of the view objects and GUI component | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  j2ee   mvc   mvc design pattern   design pattern   struts   spring   web application   web frameworks   ebay Asked in 60 Companies basic   frequent | ||||
Try 1 Question(s) Test | ||||
Frequently asked to fresh graduates and less experienced. | ||||
| ||||
Ans. Inheritance means a object inheriting reusable properties of the base class. Compositions means that an abject holds other objects. In Inheritance there is only one object in memory ( derived object ) whereas in Composition , parent object holds references of all composed objects. From Design perspective - Inheritance is "is a" relationship among objects whereas Composition is "has a" relationship among objects. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   oops   oops concepts   inheritance  object oriented programming (oops)  oops concepts   composition  object oriented programming (oops)  oops concepts   difference between   basic interview question Asked in 12 Companies basic   frequent | ||||
Try 2 Question(s) Test | ||||
Frequently asked in high end product companies. Frequently asked in Deloitte. | ||||
| ||||
Ans. https://medium.com/javarevisited/internal-working-of-hashmap-in-java-97aeac3c7beb#:~:text=HashMap%20internally%20uses%20HashTable%20implementation,the%20entries%20into%20the%20map. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  hashmap  collections  hashmap internal implementation Asked in 20 Companies expert   frequent | ||||
| ||||
Ans. 1. Query Optimization ( Query Rewriting , Prepared Statements ) 2. Restructuring Indexes. 3. DB Caching Tuning ( if using ORM ) 4. Identifying the problems ( if any ) with the ORM Strategy ( If using ORM ) | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   db   database   hibernate   orm   at&t   overstock.com   performance improvement   architecture   technical lead   architect intermediate | ||||
Frequently asked at HCL Technologies ( Based on 3 feedback ) | ||||
| ||||
Ans. Checked exceptions are the exceptions for which compiler throws an errors if they are not checked whereas unchecked exceptions are caught during run time only and hence can't be checked. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   exceptions   checked exceptions   unchecked exceptions   exception handling   checked vs unchecked exceptions Asked in 39 Companies basic   frequent | ||||
Try 1 Question(s) Test | ||||
| ||||
Ans. Vectors are synchronized whereas Array lists are not. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   basic interview question   vector   arraylist   collections   synchronization   vector vs arraylist Asked in 35 Companies basic   frequent | ||||
| ||||
Ans. Yes, We can call garbage collector directly but it doesn't guarantees that the gc will start executing immediately. This gc( ) method appears in both Runtime and System classes of java.lang package. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   garbage collection   java memory management   jvm   gc   yes no Asked in 4 Companies expert | ||||
Try 1 Question(s) Test | ||||
| ||||
Ans. In first case, there would be 2 DB calls in worst case and 1 in best case. In 2nd approach there will be always 2 DB calls. Decision on the approach should depend on the following considerations - 1. How costly is the call to DB ? Are we using indices , hibernate etc If calls to DB are costly , 1st approach should be the choice. 2. Exception Book keeping load upon exception. The benefit of saving 1st call in approach 1 should be bigger than the Book keeping for the exception. 3. Probability of the exception in first apparoach. If the DB Table is almost empty, it makes sense to follow Approach 1 as majority of the 1st calls will pass through without exception. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  database   insert-update   db exceution plan   db strategy   design   architecture   technical lead | ||||
Very Frequently asked. | ||||
| ||||
Ans. throw is used to re throw an exception.throws is used to declare that the method throws the respective exceptions.try block is used to identify if the respective block has thrown any exception.catch is used to catch the exception that has been thrown by the respective try block. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   exception handling   throw   throws   try   catch Asked in 5 Companies basic   frequent | ||||
This question can be asked in different variants like performace improvement of an application, improving performance for DB communication etc. | ||||
| ||||
Ans. This depends on entirely upon the code type. For example 1.If its just logic, we can try it to short circuit or put the if / switch case with maximum probability in the beginning. 2. Can use faster data structures, for eg - random retrieval instead of sequence / iterator 3. Working with primitive types or even bytes instead of Objects, even though it may result in marginal improvement. 4. If its service call, then service call with bulk load can help 5. If DB Operation, then with use of Indices , Views or using ORM , cache etc. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  performance improvement  code optimization Asked in 1 Companies | ||||
| ||||
Ans. GET is supposed to get information from the server. Client sends the minimal information so that Server can respond with the response body on basis of request. For example - You want to get complete employment record for employee id 123 POST is supposed to send the information for submission. Payload or a Body is usually sent so that it can be persisted on the server. For example - Sending the complete information of an employee ( id, name , dept etc ) to the server for persisting it. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  get vs post   web service   rest Asked in 11 Companies basic   frequent | ||||
| ||||
Ans. Coupling is the degree of interdependence between software modules, a measure of how closely connected two modules are or the strength of the relationships between modules. Cohesion refers to the degree to which the elements of a module belong together. Cohesion measures the strength of relationship between pieces of functionality within a given module. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  coupling  cohesion Asked in 10 Companies   frequent | ||||
| ||||
Ans. class A { void test() { System.out.println("test() method"); } } class B { void test() { System.out.println("test() method"); } } Suppose if Java allows multiple inheritance like this, class C extends A, B { } A and B test() methods are inheriting to C class. So which test() method C class will take? As A & B class test() methods are different , So here we would Facing Ambiguity. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  multiple inheritance  object oriented programming (oops)  oops concepts  diamond problem Asked in 20 Companies basic   frequent | ||||
Usually asked to entry level software developers. | ||||
| ||||
Ans. public static void main(String[] args) { int num1 = 1; int num2 = 2; num1 = num1^num2; num2 = num1^num2; num1 = num1^num2; System.out.print("num1 = " + num1 +", num2 = "+num2); } | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  code  coding Asked in 37 Companies basic   frequent | ||||
| ||||
Ans. Part of JVM which is used to load classes and interfaces. Bootstrap , Extension and System are the class loaders used by JVM. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   class loaders  classloaders   jvm   java memory management   advanced Asked in 3 Companies | ||||
| ||||
Ans. Within message.properties file. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  j2ee   web application   struts   spring Asked in 1 Companies | ||||
| ||||
Ans. Externalizable interface is used to write the state of an object into a byte stream in compressed format. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   oops   serialization   externalizable interface   interface Asked in 3 Companies | ||||
| ||||
Ans. Keep it as a Abstract Class if its a "Is a" Relationsship and should do subset/all of the functionality. Keep it as Interface if its a "Should Do" relationship. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   oops   abstract classes   interfaces   advanced Asked in 3 Companies | ||||
| ||||
Ans. Externalizable is an interface which contains two methods readExternal and writeExternal. These methods give you a control over the serialization mechanism. | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve  java   serialization   externalizable interface Asked in 2 Companies intermediate   rare | ||||
| ||||
Ans. public void checkIfAnagram(String str1,String str2){ boolean anagram = true; for(char c:str1.toCharArray()){ if(!str2.contains(String.valueOf(c))){ System.out.println("Strings are Anagrams"); anagram = false; } if(anagram == true){ System.out.println("Strings are not Anagrams"); } } } | ||||
Help us improve. Please let us know the company, where you were asked this question : | ||||
Like Discuss Correct / Improve   check if 2 strings are Anagrams Asked in 30 Companies basic   frequent | ||||