Core Java Interview Questions. Coding compilers collected list of 399 core java interview questions for freshers to experienced developers. This list of interview questions includes, java interview questions for 3 years experience, core java interview questions for senior developers, java interview questions for 2 years experience, java interview questions for 5 years experience. We are sure that after going through these java interview questions, you will be in a position to handle any java job interview. Happy learning.!
Core Java Interview Questions
| What Do You Mean By Platform Independence? |
| Are Jvm’s Platform Independent? |
| What Is A Jvm? |
| What Is The Difference Between A Jdk And A Jvm? |
| What Is A Pointer And Does Java Support Pointers? |
| What Is The Base Class Of All Classes? |
| Does Java Support Multiple Inheritance? |
| Is Java A Pure Object Oriented Language? |
| Are Arrays Primitive Data Types? |
| What Is Difference Between Path And Classpath? |
| What Are Local Variables? |
| What Are Instance Variables? |
| How To Define A Constant Variable In Java? |
| Should A Main Method Be Compulsorily Declared In All Java Classes? |
| What Is The Return Type Of The Main Method? |
| Why Is The Main Method Declared Static? |
| What Is The Arguement Of Main Method? |
| Can A Main Method Be Overloaded? |
| Can A Main Method Be Declared Final? |
| Does The Order Of Public And Static Declaration Matter In Main Method? |
| Can A Source File Contain More Than One Class Declaration? |
| What Is A Package? |
| Which Package Is Imported By Default? |
| Can A Class Declared As Private Be Accessed Outside It’s Package? |
| Can A Class Be Declared As Protected? |
| What Is The Access Scope Of A Protected Method? |
| What Is The Purpose Of Declaring A Variable As Final? |
| What Is The Impact Of Declaring A Method As Final? |
| I Don’t Want My Class To Be Inherited By Any Other Class. What Should I Do? |
| Can You Give Few Examples Of Final Classes Defined In Java Api? |
| How Is Final Different From Finally And Finalize? |
| Can A Class Be Declared As Static? |
| When Will You Define A Method As Static? |
| What Are The Restriction Imposed On A Static Method Or A Static Block Of Code? |
| I Want To Print “hello” Even Before Main Is Executed. How Will You Acheive That? |
| What Is The Importance Of Static Variable? |
| Can We Declare A Static Variable Inside A Method? |
| What Is An Abstract Class And What Is It’s Purpose? |
| Can A Abstract Class Be Declared Final? |
| What Is Use Of A Abstract Variable? |
| Can You Create An Object Of An Abstract Class? |
| Can A Abstract Class Be Defined Without Any Abstract Methods? |
| Class C Implements Interface I Containing Method M1 And M2 Declarations. Class C Has Provided Implementation For Method M2. Can I Create An Object Of Class C? |
Java Interview Questions for 2 Years ExperienceCan A Method Inside A Interface Be Declared As Final? |
| Can An Interface Implement Another Interface? |
| Can An Interface Extend Another Interface? |
| Can A Class Extend More Than One Class? |
| Why Is An Interface Be Able To Extend More Than One Interface But A Class Can’t Extend More Than One Class? |
| Can An Interface Be Final? |
| Can A Class Be Defined Inside An Interface? |
| Can An Interface Be Defined Inside A Class? |
| What Is A Marker Interface? |
| Which Oo Concept Is Achieved By Using Overloading And Overriding? |
| If I Only Change The Return Type, Does The Method Become Overloaded? |
| Why Does Java Not Support Operator Overloading? |
| Can We Define Private And Protected Modifiers For Variables In Interfaces? |
| What Is Externalizable? |
| What Modifiers Are Allowed For Methods In An Interface? |
| What Is A Local, Member And A Class Variable? |
| What Is An Abstract Method? |
| What Value Does Read() Return When It Has Reached The End Of A File? |
| Can A Byte Object Be Cast To A Double Value? |
| What Is The Difference Between A Static And A Non-static Inner Class? |
| A non-static inner class may have object instances that are associated with instances of the class’s outer class. A static inner class does not have any object instances. |
| What Is An Object’s Lock And Which Object’s Have Locks? |
| What Is The % Operator? |
| When Can An Object Reference Be Cast To An Interface Reference? |
| Which Class Is Extended By All Other Classes? |
| Which Non-unicode Letter Characters May Be Used As The First Character Of An Identifier? |
| What Restrictions Are Placed On Method Overloading? |
| What Is Transient Variable? |
| What Is Collection Api? |
| What Is Casting? |
| What Is The Return Type Of A Program’s Main() Method? |
| If A Variable Is Declared As Private, Where May The Variable Be Accessed? |
| What Do You Understand By Private, Protected And Public? |
| What Is Downcasting ? |
| What Modifiers May Be Used With An Inner Class That Is A Member Of An Outer Class? |
| How Many Bits Are Used To Represent Unicode, Ascii, Utf-16, And Utf-8 Characters? |
| What Restrictions Are Placed On The Location Of A Package Statement Within A Source Code File? |
| What Is A Native Method? |
| What Are Order Of Precedence And Associativity, And How Are They Used? |
| Can An Anonymous Class Be Declared As Implementing An Interface And Extending A Class? |
| What Is The Range Of The Char Type? |
| What Is The Range Of The Short Type? |
| Why Isn’t There Operator Overloading? |
| What Does It Mean That A Method Or Field Is “static”? |
| Is Null A Keyword? |
| Which Characters May Be Used As The Second Character Of An Identifier,but Not As The First Character Of An Identifier? |
| Is The Ternary Operator Written X : Y ? Z Or X ? Y : Z ? |
| How Is Rounding Performed Under Integer Division? |
| If A Class Is Declared Without Any Access Modifiers, Where May The Class Be Accessed? |
| Does A Class Inherit The Constructors Of Its Superclass? |
| Name The Eight Primitive Java Types. |
| What Restrictions Are Placed On The Values Of Each Case Of A Switch Statement? |
| What Is The Difference Between A While Statement And A Do Statement? |
| What Modifiers Can Be Used With A Local Inner Class? |
| When Does The Compiler Supply A Default Constructor For A Class? |
| If A Method Is Declared As Protected, Where May The Method Be Accessed? |
| What Are The Legal Operands Of The Instanceof Operator? |
| Are True And False Keywords? |
| What Happens When You Add A Double Value To A String? |
| What Is The Diffrence Between Inner Class And Nested Class? |
| Can An Abstract Class Be Final? |
| What Is Numeric Promotion? |
| What Is The Difference Between A Public And A Non-public Class? |
| To What Value Is A Variable Of The Boolean Type Automatically Initialized? |
| What Is The Difference Between The Prefix And Postfix Forms Of The ++ Operator? |
| What Restrictions Are Placed On Method Overriding? |
| What Is A Java Package And How Is It Used? |
| What Modifiers May Be Used With A Top-level Class? |
| What Is The Difference Between An If Statement And A Switch Statement? |
| Can A Method Be Overloaded Based On Different Return Type But Same Argument Type ? |
| What Happens To A Static Var That Is Defined Within A Method Of A Class ? |
| How Many Static Init Can You Have ? |
| What Is The Difference Between Method Overriding And Overloading? |
| What Is Constructor Chaining And How Is It Achieved In Java ? |
| What Is The Difference Between The Boolean & Operator And The && Operator? |
| Which Java Operator Is Right Associative? |
| Can A Double Value Be Cast To A Byte? |
Java Interview Questions for 3 Years Experience What Is The Difference Between A Break Statement And A Continue Statement? |
| Can A For Statement Loop Indefinitely? |
| To What Value Is A Variable Of The String Type Automatically Initialized? |
| What Is The Difference Between A Field Variable And A Local Variable? |
| How Are This() And Super() Used With Constructors? |
| What Does It Mean That A Class Or Member Is Final? |
| What Does It Mean That A Method Or Class Is Abstract? |
| Can An Anonymous Class Be Declared As Implementing An Interface And Extending A Class? |
| What Is The Catch Or Declare Rule For Method Declarations? |
| What Are Some Alternatives To Inheritance? |
| What Are The Different Identifier States Of A Thread? |
| What Is Garbage Collection? What Is The Process That Is Responsible For Doing That In Java? |
| What Kind Of Thread Is The Garbage Collector Thread? |
| What Is A Daemon Thread? |
| How Will You Invoke Any External Process In Java? |
| What Is The Finalize Method Do? |
| What Is Mutable Object And Immutable Object? |
| What Is The Basic Difference Between String And Stringbuffer Object? |
| What Is The Purpose Of Void Class? |
| What Is Reflection? |
| What Is The Base Class For Error And Exception? |
| What Is The Byte Range? |
| What Is The Implementation Of Destroy Method In Java.. Is It Native Or Java Code? |
| What Are The Approaches That You Will Follow For Making A Program Very Efficient? |
| What Is A Databasemetadata? |
| What Is Locale? |
| How Will You Load A Specific Locale? |
| What Is Jit And Its Use? |
| Is Jvm A Compiler Or An Interpreter? |
| What Is The Purpose Of Assert Keyword Used In Jdk1.4.x? |
| How Will You Get The Platform Dependent Values Like Line Separator, Path Separator, Etc., ? |
| Is “abc” A Primitive Value? |
| What Is Singleton? |
| Can You Instantiate The Math Class? |
| What Are The Methods In Object? |
| What Is Aggregation? |
| What Is Composition? |
| What Is Inner Class? |
| What Is Nested Class? |
| What Is The Major Difference Between Linkedlist And Arraylist? |
| What Is The Significance Of Listiterator? |
| What Is The Final Keyword Denotes? |
| What Is Skeleton And Stub? What Is The Purpose Of Those? |
| Why Does It Take So Much Time To Access An Applet Having Swing Components The First Time? |
| What Is The Difference Between Instanceof And Isinstance? |
| What Does The “final” Keyword Mean In Front Of A Variable? A Method? A Class? |
| Describe What Happens When An Object Is Created In Java? |
| What Is The Difference Amongst Jvm Spec, Jvm Implementation, Jvm Runtime ? |
| How Does Java Handle Integer Overflows And Underflows? |
| Why Are There No Global Variables In Java? |
| Whats The Difference Between Notify() And Notifyall()? |
| How Can My Application Get To Know When A Httpsession Is Removed? |
| What Interface Must An Object Implement Before It Can Be Written To A Stream As An Object? |
| What Is Your Platform’s Default Character Encoding? |
| What An I/o Filter? |
| What Is The Purpose Of Finalization? |
| Which Class Should You Use To Obtain Design Information About An Object? |
| What Is The Purpose Of The System Class? |
| Can We Use The Constructor, Instead Of Init(), To Initialize Servlet? |
| How Can A Servlet Refresh Automatically If Some New Data Has Entered The Database? |
Java Interview Questions for 4 Years Experience The Code In A Finally Clause Will Never Fail To Execute, Right? |
| How Many Messaging Models Do Jms Provide For And What Are They? |
| What Information Is Needed To Create A Tcp Socket? |
| What Class.forname Will Do While Loading Drivers? |
| How Many Jsp Scripting Elements Are There And What Are They? |
| What Are Stored Procedures? How Is It Useful? |
| How Do I Include Static Files Within A Jsp Page? |
| Why Does Jcomponent Have Add() And Remove() Methods But Component Does Not? |
| How Can I Implement A Thread-safe Jsp Page? |
| What Is The Difference Between Procedural And Object-oriented Programs? |
| What Are Encapsulation, Inheritance And Polymorphism? |
| What Is The Difference Between Assignment And Initialization? |
| What Is Oops? |
| What Are Class, Constructor And Primitive Data Types? |
| What Is An Object And How Do You Allocate Memory To It? |
| What Is The Difference Between Constructor And Method? |
| What Are Methods And How Are They Defined? |
| What Is The Use Of Bin And Lib In Jdk? |
| How Many Ways Can An Argument Be Passed To A Subroutine And Explain Them? |
| What Is The Difference Between An Argument And A Parameter? |
| How Would You Implement A Thread Pool? |
| What Are The Advantages And Disadvantages Of Reference Counting In Garbage Collection? |
| Why Java Is Said To Be Pass-by-value ? |
| What Are The Access Modifiers Available In Java? |
| What Is The Difference Between A Switch Statement And An If Statement? |
| What Are Synchronized Methods And Synchronized Statements? |
| What Are The Different Ways In Which A Thread Can Enter Into Waiting State? |
| What Is The Difference Between Static And Non Static Variables ? |
| What Is The Difference Between Notify And Notifyall Method? |
| What Are Different Type Of Exceptions In Java? |
| Explain About The Select Method With An Example? |
| Can There Be An Abstract Class With No Abstract Methods In It? |
| Can We Define Private And Protected Modifiers For Variables In Interfaces? |
| What Is Garbage Collection? What Is The Process That Is Responsible For Doing That In Java? |
| Can There Be An Abstract Class With No Abstract Methods In It? |
| Can An Interface Have An Inner Class? |
| What Is User Defined Exception? |
| What Is The Difference Between Logical Data Independence And Physical Data Independence? |
| What Are The Practical Benefits, If Any, Of Importing A Specific Class Rather Than An Entire Package (e.g. Import Java.net.* Versus Import Java.net.socket)? |
| How Many Methods Do U Implement If Implement The Serializable Interface? |
| What Does The “abstract” Keyword Mean In Front Of A Method? A Class? |
| You Can Create A String Object As String Str = “abc”; Why Cant A Button Object Be Created As Button Bt = “abc”;? Explain |
| Can Rmi And Corba Based Applications Interact ? |
| What Is Passed By Reference And Pass By Value ? |
| What Is A “stateless” Protocol ? |
| Difference Between A Class And An Object ? |
| What Are The Four Corner Stones Of Oop? |
| What Gives Java It’s “write Once And Run Anywhere” Nature? |
| How Can A Dead Thread Be Restarted? |
| What Happens If An Exception Is Not Caught? |
| What Is A Compilation Unit? |
| What Is A Task’s Priority And How Is It Used In Scheduling? |
| What Value Does Readline() Return When It Has Reached The End Of A File? |
| Can An Object’s Finalize() Method Be Invoked While It Is Reachable? |
| Does Garbage Collection Guarantee That A Program Will Not Run Out Of Memory? |
| Is Sizeof A Keyword? |
| What State Does A Thread Enter When It Terminates Its Processing? |
| Can A Lock Be Acquired On A Class? |
| How Are Observer And Observable Used? |
| What Is A Transient Variable? |
| Wha Is The Output From System.out.println(“hello”+null); ? |
| What Are E And Pi? |
| If An Object Is Garbage Collected, Can It Become Reachable Again? |
| Can An Exception Be Rethrown? |
| What Is The Purpose Of The File Class? |
| Is A Class Subclass Of Itself? |
| What Modifiers May Be Used With An Interface Declaration? |
| What Classes Of Exceptions May Be Caught By A Catch Clause? |
| What Is The Difference Between The Reader/writer Class Hierarchy And The Inputstream/outputstream Class Hierarchy? |
| Can An Object Be Garbage Collected While It Is Still Reachable? |
| What Is An Object’s Lock And Which Object’s Have Locks? |
| How Are Commas Used In The Intialization And Iteration Parts Of A For Statement? |
| What Must A Class Do To Implement An Interface? |
| What Is The Difference Between Preemptive Scheduling And Time Slicing? |
| What Restrictions Are Placed On The Location Of A Package Statement Within A Source Code File? |
| What Are Wrapped Classes? |
| Is It Possible To Specify Multiple Jndi Names When Deploying An Ejb? |
| What Is Java And Their Uses? |
| What Is Hotjava? |
| How Can You Say Java Is Object Oriented? |
| Why Java Is Platform Independent? Explain. |
| Why Java Is Secure? Explain. |
| Why Do People Says “java Is Robust”? |
| How Java Is Similar To C? |
| What’s The Difference Between Applets And Standalone Program? |
| Why Java Applets Are More Useful For Intranets As Compared To Internet? |
| How Can You Set The Applet Size? |
| How Can You Set An Applet’s Height And Width As A Percentage? |
| What Is Codebase? |
| What Is Appletviewer? |
| Explain, Java Is Compatible With All Servers But Not All Browsers? |
| What Is The Program Development Process? |
| What Is The File Type? |
| What Is Javac_g? |
| How To Optimize The Javac Output? |
| What Is The Difference Between Java Applets And Applications? |
| Can You Explain The Cs Option Of Java Interpreter? |
| What Is The Statements? |
| What Is Style And Indentation? |
| What Is The Program Compilation Process? |
| What Is Java Literals? |
| What Is The Primitive Type Byte? |
| What Is The Primitive Type Short? |
| Why Call By Value Prevents Parameter Value Change? |
| What Is Remote Method Invocation (rmi)? |
| What Is Java Jit Compilers? |
| What Is The Java Idl System? |
| What Is Java Beans? |
| What Is Object-oriented Programming? |
| What Is Abstraction? |
| What Is Encapsulation? |
| How Does The Application Server Handle The Jms Connection? |
| What Is A Superclass? |
| Explain The Abstract Class Modifier? |
| What Is The Final Class Modifier? |
| Explain The Public Class Modifier. |
| What Is The Public Field Modifier? |
| Explain The Private Field Modifier? |
| Explain The Protected Field Modifier? |
| Can You Explain The Private Protected Field Modifier? |
| What Is The Static Field Modifier? |
| What Is The Final Field Modifier? |
| Explain The Transient Field Modifier? |
| Explain The Use Of Volatile Field Modifier? |
| What Is Default Constructors? |
| What Is The Public Method Modifier? |
| What Is The Private Method Modifier? |
| What Is The Protected Method Modifier? |
| Explain The Private Protected Method Modifier? |
| Can You Explain The Final Method Modifier? |
| What Is The Abstract Method Modifier? |
| What Is The Synchronized Method Modifier? |
| Explain The Init Method? |
| What Is The Destroy Method? |
| What Is Multithreading? |
Java Interview Questions for 5 Years Experience How Java Uses The String And Stringbuffer Classes? |
| What Is The Epoch Date? |
| What Is An Arrays? |
| What Is Binary Search? |
| Can A Private Method Of A Superclass Be Declared Within A Subclass? |
| What Is Quick Sort? |
| What Is The Difference Between Final, Finally And Finalize? |
| In System.out.println( ), What Is System, Out And Println? |
| What Is Meant By “abstract Interface”? |
| What Is The Difference Between Swing And Awt Components? |
| Why Java Does Not Support Pointers? |
| What Are Parsers? Dom Vs Sax Parser. |
| What Is A Platform? |
| What Is The Main Difference Between Java Platform And Other Platforms? |
| What Is The Java Virtual Machine? |
| What Is The Java Api? |
| What Is The Package? |
| What Is Native Code? |
| Is Java Code Slower Than Native Code? |
| What Is The Serialization? |
| How To Make A Class Or A Bean Serializable? |
| How Many Methods Are There In The Serializable Interface? |
| How Many Methods Are There In The Externalizable Interface? |
| Which Containers Use A Border Layout As Their Default Layout? |
| What Is Synchronization And Why Is It Important? |
| What Are Three Ways In Which A Thread Can Enter The Waiting State? |
| What Is The Preferred Size Of A Component? |
| Can Java Object Be Locked Down For Exclusive Use By A Given Thread? |
| Can Each Java Object Keep Track Of All The Threads That Want To Exclusively Access It? |
| What Is The Purpose Of The Wait(), Notify() And Notifyall() Methods? |
| What Are The High-level Thread States? |
| What Is The Collections Api? |
| What Is The List Interface? |
| How Many Bits Are Used To Represent Unicode, Ascii, Utf-16 And Utf-8 Characters? |
| What Is The Properties Class? |
| What Is The Purpose Of The Runtime Class? |
| What Is The Purpose Of The Finally Clause Of A Try-catch-finally Statement? |
| What Is The Locale Class? |
| What Is A Protected Method? |
| What Is A Static Method? |
| What Is The Difference Between A Window And A Frame? |
| What Are Peerless Components? |
| What Is The Difference Between The Reader/writer Class Hierarchy And The Inputstream/outputstream Class Hierarchy? |
| What Is The Difference Between Throw And Throws Keywords? |
| Name Primitive Java Types? |
| How Can A Gui Component Handle Its Own Events? |
| What Advantage Do Java’s Layout Managers Provide Over Traditional Windowing Systems? |
| What Are The Problems Faced By Java Programmers Who Don’t Use Layout Managers? |
| What Is The Difference Between Static And Non-static Variables? |
| What Is The Difference Between The Paint() And Repaint() Methods? |
| What Is A Container In A Gui? |
| Is Iterator A Class Or Interface? What Is Its Use? |
| How You Can Force The Garbage Collection? |
| Describe The Principles Of Oops? |
| Explain The Encapsulation Principle? |
| Explain The Inheritance Principle? |
| How To Define An Abstract Class? |
| How To Define An Interface? |
| Explain The Polymorphism Principle? |
| Explain The Different Forms Of Polymorphism? |
| What Are Access Specifiers Available In Java? |
| What Do You Understand By A Variable? |
| What Do You Understand By Numeric Promotion? |
| Differentiate Between A Class And An Object. |
| What Is The Use Of Object And Class Classes? |
| What Do You Understand By Casting In Java Language? |
| What Are The Types Of Casting? |
| What Do You Understand By Downcasting? |
| What Do You Understand By Final Value? |
| What Are Keyboard Events? |
| What Is The Intersection And Union Methods? |
| What Are Controls And Their Different Types In Awt? |
| What Is The Difference Between Choice And List? |
| What Is The Difference Between Scrollbar And Scrollpane? |
| Which Containers Use A Flow Layout As Their Default Layout? |
| What Are Wrapper Classes? |
| What Is The Difference Between Set And List? |
| How Can The Checkbox Class Be Used To Create A Radio Button? |
| Which Textcomponent Method Is Used To Set A Textcomponent To The Read-only State? |
| What Methods Are Used To Get And Set The Text Label Displayed By A Button Object? |
| What Is The Difference Between Yield() And Sleep()? |
| How To Handle A Web Browser Resize Operation? |
| Explain The Concept Of Hashtables? |
Must Read Java Interview Questions Books 2019
- Java Interview Guide: How to Build Confidence with a Solid Understanding of Core Java Principles
- Core JAVA Interview Questions You’ll Most Likely Be Asked: Volume 8 (Job Interview Questions)
- Java / J2EE: Interview Questions You’ll Most Likely Be Asked: Volume 10 (Job Interview Questions)
- 500+ Java & J2ee Interview Questions & Answers: Java & J2ee Programming
- Java / J2EE Interview Questions: A Guide for Interview
- Java/J2EE Job Interview Companion
- Data Structures and Algorithms Made Easy in Java: Data Structure and Algorithmic Puzzles
- Cracking the C, C++ and Java Interview
- JAVA/J2EE: Interview Questions (With Set of 2 CDs)
- Java Programming Interviews Exposed (WROX)
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