Interview Question and Answers | Search Coding Interview Questions - javasearch.buggybread.com
Javasearch.buggybread.com

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.
Label / Company      Label / Company / Text

   



Interview Questions and Answers

   next 30
Frequently asked to experienced developers. Recently asked in many US interviews.
  Q61. What is database deadlock ? How can we avoid them?Database
Ans. When multiple external resources are trying to access the DB locks and runs into cyclic wait, it may makes the DB unresponsive.

Deadlock can be avoided using variety of measures, Few listed below -

Can make a queue wherein we can verify and order the request to DB.

Less use of cursors as they lock the tables for long time.

Keeping the transaction smaller.

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

   Like         Discuss         Correct / Improve     java   database   architecture     Asked in 7 Companies      expert        frequent


Almost sure to be asked in every company using any Dependency Injection framework ( Spring, Guice etc )
  Q62. What is Dependency Injection or IOC ( Inversion of Control ) ?Design
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


 Q63. Can we declare static variables as transient ?Core Java
Ans. It's weird that compiler doesn't complain if we declare transient with static variable because it makes no sense. At least a warning message saying "transient is useless in this situation" would have helped with code cleaning.

Static variables are never serialized and transient is an indication that the specified variable shouldn't be serialized so its kind of double enforcement not to serialize.

It could be that as it makes no different to the variable behavior and hence using both keywords with a variable are permitted.

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

   Like         Discuss         Correct / Improve     static  transient  serialization     Asked in 1 Companies      expert        rare

Try 1 Question(s) Test


 Q64. Which of the following are valid declarations

1. void method(int... x){};
2. void method(int.. x){};
3. void method(int.. .x){};
4. void method(int ...x){};
5. void method(int... x){};
6. void method(int ... x){};
7. void method(int x, int... y){};
8. void method(int... x, int y){};
9. void method(int... x,int... y){};
Core Java
Ans. 1st is a valid and standard declaration.

2nd results in compilation error as only 2 dots are there.

3rd results in compilation error as three dots are not consecutive and broken.

4 through 6 may not be standard and ideal way of declarations but they are valid and will compile and work fine.

7 is valid declaration.

8 and 9 will result in compilation error as var args can only be provided to last argument.

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

   Like         Discuss         Correct / Improve     var args  methods  functions   method declaration  scjp  ocjp


 Q65. How is string object immutable if we can concat a string to it ?Core Java
Ans. Because it doesn't make the change in the existing string but would create a new string by concatenating the new string to previous string. So Original string won't get changed but a new string will be created. That is why when we say

str1.concat("Hello");

It means nothing because we haven't specified the reference to the new string and we have no way to access the new concatenated string. Accessing str1 with the above code will still give the original string.

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

   Like         Discuss         Correct / Improve     string  string immutable  immutability  string concat


 Q66. Difference between JVM, JRE and JDK ?Core Java
Ans. JDK(Java Development kit) = Development Kit comprising of JVM , library and development tools for developers

JRE (Java Run time Environment) - Comprise of JVM and set of libraries

JVM(Java Virtual Machine) = Interpreter which reads the .class file line by line.

When we install JDK, JRE also get installed so we can write,compile and excute our code. Used by developer. Without JDK we can only execute the program using JRE.

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

   Like         Discuss         Correct / Improve     jvm  jre  jdk  jvm vs jre vs jdk     Asked in 4 Companies


 Q67. What the difference between S3 and EFS ?Amazon Web Services (AWS)
Ans. EFS is file storage whereas S3 is object storage.

EFS is filesystem presented over IP network as normal OS drive, while S3 is HTTP accessed store.

EFS is capable of being mounted whereas S3 doesn't.

S3 has capabilities beyond just filesystem, there is whole metadata part where you can store info about your objects in S3.

As S3 is accessed over http , it's capable of hosting a static web site on it's own whereas EFS needs a computing and frontend service to have such capability.

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

   Like         Discuss         Correct / Improve     aws s3  aws storage  amazon cloud storage  amazon s3  aws ehs  aws s3  aws storage  amazon cloud storage  amazon s3 vs aws efs


Very Frequently asked across all type of companies and across all levels.
  Q68. Difference between Public, Private, Default and Protected ?Core Java
Ans. Private - Not accessible outside object scope.

Public - Accessible from anywhere.

Default - Accessible from anywhere within same package.

Protected - Accessible from object and the sub class objects.

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

   Like         Discuss         Correct / Improve     java   oop   access specifier   public   private   default   protected   public vs private vs default vs protected     Asked in 12 Companies      basic        frequent

Try 1 Question(s) Test


 Q69. Does Constructor creates the object ?Core Java
Ans. New operator in Java creates objects. Constructor is the later step in object creation. Constructor's job is to initialize the members after the object has reserved memory for itself.

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

   Like         Discuss         Correct / Improve     java   constructor   object creation      intermediate        rare


 Q70. What will this code print ?

String a = new String ("TEST");
String b = new String ("TEST");
if(a == b) {
System.out.println ("TRUE");
} else {
System.out.println ("FALSE");
}
Core Java
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.

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

   Like         Discuss         Correct / Improve     string   string class   java   ==   object references   coding     Asked in 2 Companies      basic        frequent

Try 1 Question(s) Test


 Q71. Can constructors be synchronized in Java ?Core Java
Ans. No. Java doesn't allow multi thread access to object constructors so synchronization is not even needed.

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

   Like         Discuss         Correct / Improve     synchronization   synchronize   constructor   java   multithreading   yes-no   advanced     Asked in 1 Companies      expert        rare


Frequently asked question for intermediate developers. Frequently asked in HCL Technologies and EPAM.
  Q72. What is Volatile keyword used for ?Core Java
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


 Q73. Will this code give error if i try to add two heterogeneous elements in the arraylist. ? and Why ?

List list1 = new ArrayList<>();
list1.add(5);
list1.add("5");
Ans. If we don't declare the list to be of specific type, it treats it as list of objects.

int 1 is auto boxed to Integer and "1" is String and hence both are objects.

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

   Like         Discuss         Correct / Improve     java   collections   arraylist   list   autoboxing   wrapper classes      expert        rare


Advanced level question. Recently asked in few Indian service companies ( Based on 3 inputs )
 Q74. What are various types of Class loaders used by JVM ?Core Java
Ans. Bootstrap - Loads JDK internal classes, java.* packages.

Extensions - Loads jar files from JDK extensions directory - usually lib/ext directory of the JRE

System - Loads classes from system classpath.

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

   Like         Discuss         Correct / Improve     java   jvm   memory management   class loaders   bootstrap   extensions   system  classloaders   advanced   technical lead   technical architect     Asked in 7 Companies


  Q75. Difference between SAX and DOM Parser ?Xml
Ans. A DOM (Document Object Model) parser creates a tree structure in memory from an input document whereas A SAX (Simple API for XML) parser does not create any internal structure.

A SAX parser serves the client application always only with pieces of the document at any given time whereas A DOM parser always serves the client application with the entire document no matter how much is actually needed by the client.

A SAX parser, however, is much more space efficient in case of a big input document whereas DOM parser is rich in functionality.

Use a DOM Parser if you need to refer to different document areas before giving back the information. Use SAX is you just need unrelated nuclear information from different areas.

Xerces, Crimson are SAX Parsers whereas XercesDOM, SunDOM, OracleDOM are DOM parsers.

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

   Like         Discuss         Correct / Improve     java   xml   parsers   sax   dom parser   difference   architecture   technical lead   technical architect  markup language   sax vs dom     Asked in 14 Companies        frequent

Try 1 Question(s) Test


Very frequently asked.Usually among first few questions.
  Q76. What is MVC ? Design
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


 Q77. How compiler handles the exceptions in overriding ?Core Java
Ans. 1)The overriding methods can throw any runtime Exception , here in the case of runtime exception overriding method (subclass method) should not worry about exception being thrown by superclass method.

2)If superclass method does not throw any exception then while overriding, the subclass method can not throw any new checked exception but it can throw any runtime exception

3) Different exceptions in java follow some hierarchy tree(inheritance). In this case , if superclass method throws any checked exception , then while overriding the method in subclass we can not throw any new checked exception or any checked exception which are higher in hierarchy than the exception thrown in superclass method

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

   Like         Discuss         Correct / Improve     java   overriding   exceptions   inheritence   inheritance  object oriented programming (oops)  oops concepts   oops


 Q78. What things should be kept in mind while creating your own exceptions in Java?Core Java
Ans. All exceptions must be a child of Throwable.

If you want to write a checked exception that is automatically enforced by the Handle or Declare Rule, you need to extend the Exception class.

You want to write a runtime exception, you need to extend the RuntimeException class.

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

   Like         Discuss         Correct / Improve     java   exceptions   exception handling   user defined exceptions   throwable   architecture   library development   technical architect   technical lead


Frequently asked to fresh graduates and less experienced.
  Q79. Difference between Composition and Inheritance ?Core Java
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


 Q80. How to find whether a given integer is odd or even without use of modulus operator in java?Core Java
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 ");
}
}

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

   Like         Discuss         Correct / Improve     java   code   coding   tricky questions   interesting questions   modulus operator     Asked in 4 Companies        frequent


 Q81. What will be the output of following code ?

public static void main(String[] args){
String name = null;
File file = new File("/folder", name);
System.out.print(file.exists());
}
Core Java
Ans. NullPointerException

at line: "File file = new File("/folder", name);"

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

   Like         Discuss         Correct / Improve     java   io   file   fileio   coding   code   file handling


 Q82. Which annotations are used in Hibernate ?Hibernate
Ans. @Entity
@Table
@Id
@Column
@Temporal
@Basic
@Enumerated
@Access
@Embeddable
@Lob
@AttributeOverride
@Embedded
@GeneratedValue
@ElementCollection
@JoinTable
@JoinColumn
@CollectionId
@GenericGenerator
@OneToOne
@OneToMany
@ManyToOne
@ManyToMany
@NotFound

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

   Like         Discuss         Correct / Improve     hibernate   annotations


Not frequently asked as it was introduced with Java 8.
 Q83. What is StringJoiner ?Core Java
Ans. StringJoiner is a util method to construct a string with desired delimiter. This has been introduced with wef from Java 8.

Sample Code

StringJoiner strJoiner = new StringJoiner(".");
strJoiner.add("Buggy").add("Bread");
System.out.println(strJoiner); // prints Buggy.Bread


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

   Like         Discuss         Correct / Improve     java   java8   java 8   string   stringjoiner


 Q84. Which access specifiers can be used with top level class ? a. public or default b. public or private c. public or protected d. protected or defaultCore Java
Ans. public or default

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

   Like         Discuss         Correct / Improve     access specifier   oops   java   class     Asked in 2 Companies


 Q85. Which of the following can be marked static ?

a. Methods , Variables and Initialization Blocks.
b. Methods , Variables , Initialization Blocks and Outer Classes and nested Classes.
c. Methods , Variables , Initialization Blocks and Outer Classes.
d. Methods , Variables , Initialization Blocks and nested Classes
Core Java
Ans. Methods , Variables , Initialization Blocks and nested Classes

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

   Like         Discuss         Correct / Improve     oops   java   static   nested classes   static nested classes

Try 2 Question(s) Test


 Q86. Which of the following is false about main method ?

a. It should be declared public and static
b. it should have only 1 argument of type String array
c. We can override main method
d. We can overload main method
Core Java
Ans. We can override main method

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

   Like         Discuss         Correct / Improve     java   main method


 Q87. What is the difference between the following two code lines ?

1. new OuterClass().new InnerClass();

2. new OuterClass.InnerClass();
Core Java
Ans. In first case we are trying to initialize Inner class object using the instance of Outer Class whereas in second case we are trying to initialize the Inner class object directly using the Outer class name.

In second case , Inner class is "static inner class" as we cannot access "non static inner class" using Classname alone.

In first case, the inner class could be either "static inner class" or "non static inner class".

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

   Like         Discuss         Correct / Improve     inner classes  inner class   static inner class   new operator


 Q88. What are the different uses of Interfaces in Java ?Core Java
Ans. 1. Regulation / Enforcement / Policy / Contract , It's primary use

2. Use as a collection of utility methods(since java 8 through default methods)

3. Collecting constants together, As Interface are lighter, it makes sense to use them instead of classes if no getters and setters required.

4. Creation of Custom Annotations

5. Special services like marker interface

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

   Like         Discuss         Correct / Improve     interfaces   uses of interfaces in java     Asked in 1 Companies


 Q89. What do you look for when you do code review ?Core Java
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.

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

   Like         Discuss         Correct / Improve     code review  clean code     Asked in 1 Companies      intermediate        frequent


 Q90. Can we have multiple main methods in a single class ?Core Java
Ans. We can overload the main method by specifying different argument types. For example -

2 main methods with different arguments is perfectly legal

public static void main();
public static void main(String[] args);

The following are not legal as compiler will complain of duplicate methods

public static void main(String[] args);
public static void main(String[] args);

Even The following are not legal as we cannot overload on return types

public static String main(String[] args);
public static void main(String[] args);

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

   Like         Discuss         Correct / Improve     main method     Asked in 2 Companies


previous 30   next 30

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

Any input from you will be highly appreciated and It will unlock the application for 10 more requests.

Company Name:
Questions Asked: