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Interview Questions and Answers - Order By Rating | ||||
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Ans. We are using Apache 2.3 and Tomcat 5.6 | ||||
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Like Discuss Correct / Improve  web server  application server  server Basic   frequent | ||||
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Ans. It depends on the type of inner class To access non static inner class method new OuterClass().new InnerClass().getMethod(); To access static method of static inner class new OuterClass.InnerClass().getMethod(); | ||||
Sample Code for inner class | ||||
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Like Discuss Correct / Improve  inner classes  nested aclasses Asked in 1 Companies Intermediate   frequent | ||||
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Ans. 1. Objects are serialized and not classes and hence Static variables are ignored. 2. Transient is an explicit declaration to ignore the variable during serialization and hence transient instance variables are ignored too. 3. Base class instance variables if the base class hasn't been declared serializable. | ||||
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Like Discuss Correct / Improve  serialization Asked in 1 Companies intermediate   frequent | ||||
Try 1 Question(s) Test | ||||
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Ans. PATH, CLASSPATH and JAVA_HOME | ||||
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Like Discuss Correct / Improve  environment variables  path  classpath  java_home Asked in 3 Companies basic   frequent | ||||
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This question was recently asked at 'HeadStrong,ServiceNow'.This question is still unanswered. Can you please provide an answer. | ||||
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Like Discuss Correct / Improve  Search Algorithm  Sorting Algorithm Asked in 2 Companies basic   frequent | ||||
Very frequently asked. Usually asked in this format or as difference with interfaces / concrete classes. | ||||
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Ans. Abstract class is the class that is not supposed to be instantiated. The purpose of the class to only have extension to the derived class. | ||||
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Like Discuss Correct / Improve  abstract class Asked in 6 Companies basic   frequent | ||||
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Ans. static keyword is used to specify that the respective programming construct ( method , variable ) belongs to the class and not to its instance and is supposed to be shared by all instances of the class. | ||||
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Like Discuss Correct / Improve  static keyword Asked in 1 Companies basic   frequent | ||||
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Ans. [Open Ended Answer] | ||||
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Like Discuss Correct / Improve   Asked in 2 Companies   frequent | ||||
Frequently asked in Cognizant ( Based on 2 feedback ) | ||||
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Ans. Inner join is the intersection of two tables on the condition defined by the where clause i.e will get records from both tables matched by a column. Outer join is the union of two tables i.e will get all records from both tables and will put null in the columns where related records are not present. Left Outer join is the left union of two tables i.e all records from the table on the left and values from the right table for related records else null for the columns from right table. Right Outer join is the right union of two tables i.e all records from the table on the right and values from the left table for related records else null for the columns from left table. | ||||
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Like Discuss Correct / Improve  sql  inner join  outer join  right join  left join Asked in 24 Companies basic   frequent | ||||
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Ans. An Exception in java is the occurrence during computation that is anomalous and is not expected. Exception handling is the mechanism which is used to handle such situations. | ||||
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Like Discuss Correct / Improve  exception handling Asked in 18 Companies basic   frequent | ||||
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Ans. https://en.wikipedia.org/wiki/Database_normalization | ||||
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Like Discuss Correct / Improve  normalization  database Asked in 35 Companies intermediate   frequent | ||||
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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. | ||||
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Like Discuss Correct / Improve  multiple inheritance  object oriented programming (oops)  oops concepts  diamond problem Asked in 20 Companies basic   frequent | ||||
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Ans. Throwable | ||||
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Like Discuss Correct / Improve   Asked in 1 Companies basic   frequent | ||||
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Ans. Static , Final , Synchronized, private , public , protected, volatile, transient, super, this,import , abstract,native,default (effective java 8), new | ||||
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Like Discuss Correct / Improve  java keywords   frequent | ||||
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Ans. Object Oriented - Java is object oriented but isn't purely object oriented as we have primitives along with objects. Platform Independent - As JVM provides the translation to the Machine code as per the underlying Operating System. Interpreted as well as compiled - Java files are compiled as class files and then class files are interpreted by JVM. Runs on a Virtual Machine - Which is JVM that acts as an independent sub environment. Multi-threaded - As applications can run on single thread as well as multi thread. Modularity - Through usage of Classes , methods and Interfaces. Robust Usage in variety of Application types - Web , Gaming, BigData. | ||||
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Ans. Modularity - First sign of good code is whether it has been segregated into methods and classes appropriately. I dont mind it in excess because I believe that is forward looking strategy as applications tends to expand and eventually become hard to read. Self Explanatory - Variables and methods should be named in a way that the code should be self explanatory even without comments. Use of Constant variables to explain use of literal. Proper Code Reuse - If there is anything being reused , it should be moved to parent classes / methods. Proper composition calls - Composed hierarchy should not be access in just single line. One or two levels is ok but having multiple levels make it hard to read and debug. | ||||
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Like Discuss Correct / Improve  code review  clean code Asked in 1 Companies intermediate   frequent | ||||
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Ans. Maven is a build automation tool used primarily for Java projects. | ||||
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Like Discuss Correct / Improve  maven  build Asked in 6 Companies basic   frequent | ||||
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Ans. 500 is Internal Server Error 404 is resource not found 400 is Bad Request 403 is Forbidden 401 is Unauthorized 200 is OK | ||||
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Like Discuss Correct / Improve  http  http status codes Asked in 2 Companies   frequent | ||||
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Ans. Collections in java is a framework of classes that provides an abstracted data structure to store and manipulate the group of objects. Each class is unique in the way it stores , search , sort and modify the elements. | ||||
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Like Discuss Correct / Improve  collections  collection classes Asked in 1 Companies Basic   frequent | ||||
Frequently asked in Accenture. | ||||
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Ans. [Open Ended Answer] | ||||
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Like Discuss Correct / Improve  general question  non technical question Asked in 20 Companies   frequent | ||||
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Ans. An Error indicates serious problems that a reasonable application should not try to catch whereas An Exception indicates conditions that a reasonable application might want to catch. | ||||
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Like Discuss Correct / Improve  error  exception handling  exceptions Asked in 2 Companies basic   frequent | ||||
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Ans. <a href="http://javahungry.blogspot.com/2015/03/difference-between-array-and-arraylist-in-java-example.html" rel="nofollow">http://javahungry.blogspot.com/2015/03/difference-between-array-and-arraylist-in-java-example.html</a> | ||||
Sample Code for ArrayList | ||||
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Like Discuss Correct / Improve  array  arraylist Asked in 11 Companies basic   frequent | ||||
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Ans. A Web service is a service offered by one system to another, for communication over web through http. XML are JSON are usually used for sending across information from one system to another. | ||||
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Like Discuss Correct / Improve  web service Asked in 2 Companies basic   frequent | ||||
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Ans. https://www.mongodb.com/scale/nosql-vs-relational-databases | ||||
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Like Discuss Correct / Improve  database management  nosql database  relational database Asked in 1 Companies   frequent | ||||
Frequently asked in high end product companies. Frequently asked in Deloitte. | ||||
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Ans. https://medium.com/javarevisited/internal-working-of-hashmap-in-java-97aeac3c7beb#:~:text=HashMap%20internally%20uses%20HashTable%20implementation,the%20entries%20into%20the%20map. | ||||
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Like Discuss Correct / Improve  hashmap  collections  hashmap internal implementation Asked in 20 Companies expert   frequent | ||||
Very Frequently asked to Senior Software Engineers or Developers. | ||||
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Ans. [Open Ended Answer] | ||||
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Like Discuss Correct / Improve  design patterns Asked in 17 Companies intermediate   frequent | ||||
Frequently asked Generic Question. | ||||
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Ans. [Open Ended Answer] Usually answered stating your keen interest in the role offered and challenges and opportunities the role offers. | ||||
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Like Discuss Correct / Improve   Asked in 42 Companies   frequent | ||||
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Ans. 1. Static class is a class which cannot be instantiated and all its members are static whereas Singleton is the class that only permit creation of single object and then the object is reused. 2. As there is no object in Static class, it cannot participate in runtime Polymorphism. 3. As Static class doesnt allow creating objects and hence it cannot be serialized. 4. Static class body is initialized eagerly at application load time whereas Singleton object can be initiated eagerly using static blocks or lazily on first need. 5. Its not recommended to use pure static class as it fails to use many OOPs concepts. | ||||
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Like Discuss Correct / Improve  Static Class  Singleton  Static Class vs Singleton Asked in 3 Companies Intermediate   frequent | ||||
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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"); } } } | ||||
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Like Discuss Correct / Improve   check if 2 strings are Anagrams Asked in 30 Companies basic   frequent | ||||
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Ans. https://en.wikipedia.org/wiki/Agile_software_development | ||||
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Like Discuss Correct / Improve  software development process  agile Asked in 5 Companies   frequent | ||||