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Interview Questions and Answers for 'Cod' - 183 question(s) found - Order By Newest | ||||
Very frequently asked. Among first few questions in almost all interviews. Among Top 5 frequently asked questions. Frequently asked in Indian service companies (HCL,TCS,Infosys,Capgemini etc based on multiple feedback ) and Epam Systems | ||||
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Ans. "equals" is the method of object class which is supposed to be overridden to check object equality, whereas "==" operator evaluate to see if the object handlers on the left and right are pointing to the same object in memory. x.equals(y) means the references x and y are holding objects that are equal. x==y means that the references x and y have same object. Sample code: String x = new String("str"); String y = new String("str"); System.out.println(x == y); // prints false System.out.println(x.equals(y)); // prints true | ||||
Sample Code for equals | ||||
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Like Discuss Correct / Improve  java   string comparison   string   object class   ==   equals   object equality  operator   == vs equals   equals vs == Asked in 294 Companies basic   frequent | ||||
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Advanced level question. Frequently asked in High end product companies. Frequently asked in Google , Cognizant and Deloitte ( Based on 2 feedback ) | ||||
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Ans. 1. String Pool - When a string is created and if it exists in the pool, the reference of the existing string will be returned instead of creating a new object. If string is not immutable, changing the string with one reference will lead to the wrong value for the other references. Example - String str1 = "String1"; String str2 = "String1"; // It doesn't create a new String and rather reuses the string literal from pool // Now both str1 and str2 pointing to same string object in pool, changing str1 will change it for str2 too 2. To Cache its Hashcode - If string is not immutable, One can change its hashcode and hence it's not fit to be cached. 3. Security - String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment. | ||||
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Like Discuss Correct / Improve  java   oops   string   string class   immutable  immutability   advanced Asked in 39 Companies expert   frequent | ||||
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Ans. OOPs or Object Oriented Programming is a Programming model which is organized around Objects instead of processes. Instead of a process calling series of processes, this model stresses on communication between objects. Objects that all self sustained, provide security by encapsulating it's members and providing abstracted interfaces over the functions it performs. OOP's facilitate the following features 1. Inheritance for Code Reuse 2. Abstraction for modularity, maintenance and agility 3. Encapsulation for security and protection 4. Polymorphism for flexibility and interfacing | ||||
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Like Discuss Correct / Improve  oops  oops features Asked in 260 Companies basic   frequent | ||||
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Ans. 1. Stack Segment - Contains primitives, Class / Interface names and references. 2. Heap Segment - Contains all created objects in runtime, objects only plus their object attributes (instance variables), Static variables are also stored in heap. 3. Code Segment - The segment where the actual compiled Java bytecodes resides when loaded | ||||
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Like Discuss Correct / Improve  java   memory   memory management   stack memory   heap memory   code segment memory   advanced Asked in 9 Companies expert   frequent | ||||
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Frequently asked in all types of companies especially Indian Services companies. Frequently asked in CTS (Based on 2 feedback) | ||||
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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. | ||||
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Like Discuss Correct / Improve  java   collections   hashcode   advanced  hashtable Asked in 33 Companies intermediate   frequent | ||||
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Very frequently asked. Favorite question in Walk in Drive of many Indian service companies. | ||||
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Ans. Its a method which cannot be overridden. Compiler throws an error if we try to override a method which has been declared final in the parent class. | ||||
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Like Discuss Correct / Improve  java   oops   final   final method Asked in 30 Companies basic   frequent | ||||
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Almost sure to be asked in every company using any Dependency Injection framework ( Spring, Guice etc ) | ||||
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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. | ||||
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Like Discuss Correct / Improve  design patterns   ioc ( Inversion of Control )  dependency injection Asked in 83 Companies intermediate   frequent | ||||
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Ans. FALSE. == operator compares object references, a and b are references to two different objects, hence the FALSE. .equals method is used to compare string object content. | ||||
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Like Discuss Correct / Improve  string   string class   java   ==   object references   coding Asked in 2 Companies basic   frequent | ||||
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Very frequently asked.Usually among first few questions. | ||||
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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 | ||||
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Like Discuss Correct / Improve  j2ee   mvc   mvc design pattern   design pattern   struts   spring   web application   web frameworks   ebay Asked in 60 Companies basic   frequent | ||||
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Ans. public static void main(String ar[]) { int n=5; if((n/2)*2==n) { System.out.println("Even Number "); } else { System.out.println("Odd Number "); } } | ||||
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Like Discuss Correct / Improve  java   code   coding   tricky questions   interesting questions   modulus operator Asked in 4 Companies   frequent | ||||
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Ans. NullPointerException at line: "File file = new File("/folder", name);" | ||||
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Like Discuss Correct / Improve  java   io   file   fileio   coding   code   file handling | ||||
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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. There can be two different elements with the same hashcode. When two elements have the same hashcode then Java uses the equals to further differentation. So there can be one or two objects depending on the content of the objects. | ||||
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Like Discuss Correct / Improve  java   hashcode   map   hashmap   object reference   advanced Asked in 1 Companies | ||||
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Ans. Unicode requires 16 bits and ASCII require 7 bits. Although the ASCII character set uses only 7 bits, it is usually represented as 8 bits. UTF-8 represents characters using 8, 16, and 18 bit patterns. UTF-16 uses 16-bit and larger bit patterns. | ||||
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Ans. Java uses Just-In-Time compiler to enable high performance. Just-In-Time compiler is a program that turns Java bytecode into instructions that can be sent directly to the processor. | ||||
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Ans. It will create the file myfile.txt in the current directory. | ||||
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Ans. Inheritance | ||||
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Like Discuss Correct / Improve  java   java concepts   java features   code reusability | ||||
This question can be asked in different variants like performace improvement of an application, improving performance for DB communication etc. | ||||
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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. | ||||
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Like Discuss Correct / Improve  performance improvement  code optimization Asked in 1 Companies | ||||
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This question was recently asked at 'Ariba'.This question is still unanswered. Can you please provide an answer. | ||||
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Like Discuss Correct / Improve  code  coding.string  trim a string Asked in 1 Companies | ||||
Usually asked to entry level software developers. | ||||
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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); } | ||||
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Like Discuss Correct / Improve  code  coding Asked in 37 Companies basic   frequent | ||||
Very frequently asked. Usually asked with questions related to String. Frequently asked at CTS / Cognizant | ||||
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Ans. Object that can't be changed after instantiation. | ||||
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Ans. private static boolean isPalindrome(String str) { if (str == null) return false; StringBuilder strBuilder = new StringBuilder(str); strBuilder.reverse(); return strBuilder.toString().equals(str); } | ||||
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Like Discuss Correct / Improve  java   string   stringbuilder   stringbuilder   string class   code   palindrome Asked in 38 Companies Basic   frequent | ||||
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Ans. private static String removeChar(String str, char c) { | ||||
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Like Discuss Correct / Improve  java   string   string class   code   write code | ||||
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Ans. Since String is immutable, its hashcode is cached at the time of creation and it doesnt need to be calculated again. This makes it a great candidate for key in a Map and its processing is fast than other HashMap key objects. This is why String is mostly used Object as HashMap keys. | ||||
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Like Discuss Correct / Improve  java   string class   string   immutable  immutability   hashmap   immutable  immutability   hashcode   hash code   advanced Asked in 2 Companies expert   frequent | ||||
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Ans. Yes. static method is not accessed by the instance of class. Either you call it by the class name or the reference. | ||||
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Like Discuss Correct / Improve  java   static   static method   code | ||||
Very frequently asked in HCL Tech ( Based of 4 inputs ) | ||||
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Ans. Using String method - new StringBuffer(str).reverse().toString(); Iterative - public static String getReverseString(String str){ StringBuffer strBuffer = new StringBuffer(str.length); for(int counter=str.length -1 ; counter>=0;counter--){ strBuffer.append(str.charAt(counter)); } return strBuffer; } Recursive - public static String getReverseString(String str){ if(str.length <= 1){ return str; } return (getReverseString(str.subString(1)) + str.charAt(0); } | ||||
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Like Discuss Correct / Improve  java   string   reverse   stringbuffer   string class   code Asked in 6 Companies   frequent | ||||
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Ans. true, due to String Pool, both will point to a same String object. | ||||
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Like Discuss Correct / Improve  java   code   coding   tricky questions   interesting questions   string   string pool   .equal   == intermediate   frequent | ||||
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Ans. Compile time error as it won't find the constructor matching BuggyBread2(). Compiler won't provide default no argument constructor as programmer has already defined one constructor. Compiler will treat user defined BuggyBread2() as a method, as return type ( void ) has been specified for that. | ||||
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Ans. Yes. | ||||
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Like Discuss Correct / Improve  java   io   file   fileio   coding   code   objectoutputstream   fileoutputstream   yesno  file handling | ||||
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Ans. matcher.find() should have been used instead of matcher.next() within while. | ||||
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Like Discuss Correct / Improve  java   regex   pattern.matcher   java.util   coding   code | ||||