File Name: java frequently asked interview questions and answers .zip
I was getting a lot of emails and comments to create java interview questions and answers PDF eBook.
Can you please share a list of frequently asked Java programs on Interviews as well? Interesting question, some of the frquently asked programs on Java interviews are : - reverse string without using stringbuffer - writing code to avoid deadlock - four ways to loop over map - multi-threaded version of getInstance method of Singleton class - count number of 1 in an integer number - converting string to bytes etc.
Great article. In 5, the Singleton example - you may want to show the private constructor method for the SingletonClass. As written, you could create multiple instances of the SingletonClass, each with their own DCL object. Couple of core Java questions which have seen more frequently on interviews are : - can two unequal object has same hashcode?
I like to contribute because I have benefitted a lot from your side : Thank you very much for your time and effort. I love Java interviews, most of the time you will see these repeated, frequently asked question, which even a kid can answer. If you are a Java Developer of just couple of month of experience but has a computer science degree, I would say to prepare well for DS and Algo, you can check some sample Data structure questions here, once you are good at that, just prepare some basic Java questions for telephonic round.
Once you are done that you are ready, but if you want more confidence, you should check this Mega list of Java questions , which contains core Java questions including multi-threading, exception handling, collections, GC, design pattern and OOP questions from last 5 years of Java interviews.
This will help you to clear any Java job interview, at least for small companies. At In single threaded applications you may actually get no locking at all on a Hashtable. Now, we usually ask like these.
What is theJMM? Do you know synchronized. What is the lock's upgrade and downgrade? What is the AQS? Can you explain ThreadPoolExecutor's params? Spring Bean lifecycle. Good questions, would be glad you can provide the answers as well for people reading comments, I always do :- Even I don't know answers of some of these questions like synchronized. Same with AQS, unless I am missing something.
Feel free to comment, ask questions if you have any doubt. Pages Home core java spring online courses thread java 8 coding sql books oop interview certification free resources best. I call them frequently asked Java interview questions, and I suggest every Java developer make a list of them for their own reference and revision.
I am sure many Java programmer already has such list of questions handy if you don't have then this is a good time to find and make your own list, or if you are in rush then you can also buy my book Grokking the Java Interview , which contains many such questions.
These are the questions which you simply can't afford to miss, especially at freshers level. They appear at various stages of Java interviews. Most likely you will see them on a telephonic round, where the Interviewer just wants to filter candidates between who knows Java and who doesn't. The good thing about them is that they are so common that everyone knows about them. Though for freshers it could be a little difficult, as your experience grows these frequently asked questions become much easier to answer.
In this list, I am sharing some of the most frequently asked questions from Java interviews. I will also add some more questions on this list but for now let's start with these 21 questions. You will mostly see these questions on telephonic round of your interview, but it is also asked a lot of time during face to face interviews.
By the way, some questions are really easy, and some are real tough, so it's mixed of both, but one thing is common, they are the most frequently asked questions from Java interviews. Java achieve this by using Java virtual machine, when Java programs are compiled they are converted to.
So the same Java program can run on any operating system only JVM can differ according to OS but all JVM can understand converted byte code that's how Java achieve platform independence.
System class loader. I have included this in my list of frequently asked questions from Java interviews because I have seen it more often than not. At a bare minimum I suggest you get yourself familiar with essential coding patterns like sliding window, merge interval, two pointers approach, and top k elements, this will help you a lot in solving coding problems on Java interviews. It's an interactive course to learn 15 essential coding patterns for interviews. Answer : If I say that this is one of the most most frequently asked question to Java programmers, then it would not be wrong.
Here are some important differences between these two classes : ArrayList implements List interface while HashSet implements Set interface in Java.
ArrayList is an ordered collection and maintains insertion order of elements while HashSet is an unordered collection and doesn't maintain any order. ArrayList allow duplicates while HashSet doesn't allow duplicates. One more difference between HashSet and ArrayList is that its index based you can retrieve object by calling get index or remove objects by calling remove index while HashSet is completely object based.
HashSet also doesn't provide get method. On the same note, collections are very important topics for Java interviews, I highly recommend you to prepare this topic well, If you need resources, you can check out these Java Collections and Streams Courses to start with.
Answer : Interviewer will never stop asking this question. It's mother of all frequently asked question in Java. Answer: This is usually a follow-up of the previous Java questions. There are more than one ways to do it. You can further see my article for a code example to create a thread-safe singleton in Java. So we can use volatile to achieve synchronization because its guaranteed that all reader thread will see updated value of volatile variable once write operation completed, without volatile keyword different reader thread may see different values.
The volatile modifier also helps to prevent reordering of code by compiler and offer visibility guarantee by happens-before relationship. See this article to learn more about volatile in Java. Answer: Transient in Java is used to indicate that the variable should not be serialized. Serialization is a process of saving an object's state in Java. When we want to persist and the object's state by default all instance variables in the object are stored.
So, declare those variables as transient. If the variable is declared as transient, then it will not be persisted. This is the main purpose of the transient keyword, to learn more about transient variable in Java, see this tutorial. Answer : This is again follow-up of previous two Java questions. You will see this question on top 10 on any list of Java frequently asked question. Here are some of the important difference between them. Transient variable : transient keyword is used with those instance variable which will not participate in serialization process.
Answer: If I say this is one of the most frequently asked Java questions on both face-to-face and telephonic interview then it would be an exaggeration. It's triggered by implementing Serializable interface which is a marker interface an interface without any method. While Externalizable is used to customize and control default serialization process which is implemented by application. Main difference between these two is that Externalizable interface provides complete control to the class implementing the interface whereas Serializable interface normally uses default implementation to handle the object serialization process.
Externalizable interface has two method writeExternal ObjectOutput and readExternal ObjectInput method which are used to handle customized object serialize process and in terms of performance its good because everything is under control. Answer : No, we cannot override private methods in Java as if we declare any variable ,method as private that variable or method will be visible for that class only, and also if we declare any method as private than they are bonded with class at compile time not in run time so we cant reference those method using any object so we cannot override private method in Java.
Answer: This is another frequently asked question from the Java interview. Main difference between HaspMap and Hashtable are the following : HashMap allows null values as key and value whereas Hashtable doesn't allow nulls. Hashtable is thread-safe and can be shared between multiple threads whereas HashMap cannot be shared between multiple threads without proper synchronization. Because of synchronization, Hashtable is considerably slower than HashMap, even in case of single threaded application.
Hashtable is a legacy class, which was previously implemented Dictionary interface. It was later retrofitted into Collection framework by implementing Map interface.
On the other hand, HashMap was part of framework from it's inception. You can also make your HashMap thread-safe by using Collections. It's performance is similar to Hashtable. See here to learn more and understand when to use Hashtable and HashMap in Java. The List interface can have many null objects but the set permits only one null element.
This question is some time also asked as difference between Map , List and Set to make it more comprehensive as those three are major data structure from Java's Collection framework. To answer that question see this article. Answer: One more favorite of Java Interviewers, there is hardly any interview of junior Java developers, on which this question doesn't appear.
In four and five rounds of interviews, you will definitely going to see this question in some point of time. Vector and ArrayList both implement the list interface but main difference between these two is vector is synchronized and thread safe but list is not because of this list is faster than vector. To learn more about how ConcurrentHashMap achieves it's thread-safety, scalability using lock stripping and non blocking algorithm, see this article as well.
Answer: equals and hashCode methods needs to be override for an object to be used as key in HaspMap. In Map objects are stored as key and values. While retrieving get key method is used at this time hash code of key object is calculated and then equals method is called to compare value object.
It is just used to put current thread on sleep. Object class while sleep is defined in java. Thread class 18 Difference between notify and notifyAll in Java? If you are sure that more than one thread is waiting on the monitor and you want all of them to give equal chance to compete for CPU, use notifyAll method. See here more differences between notify vs notifyAll. Answer: HashMap's performance depends on two things first initial capacity and second load factor whenever we create HashMap initial capacity number of bucket is created initially and load factor is criteria to decide when we have to increase the size of HashMap when its about to get full.
We can set classpath we need to include all those directory where we have put either our.
Download PDF We have compiled the most frequently asked Java Interview Questions and Answers that will help you prepare for the Basic Java interview questions that an interviewer might ask you during your interview. In this list of Basic Java interview questions, we have covered all commonly asked basic and advanced Core Java interview questions with detailed answers to help you clear the job interview. The following list contains important Core Java interview questions for freshers as well as Java interview questions and answers for experienced programmers to help them prepare for the interview. This detailed guide of interview questions for Java Programming will help you to crack your Job interview easily. What is the difference between an Inner Class and a Sub-Class?
In this article, we have compiled the most frequently asked Java Interview Questions. These questions will give you an acquaintance with the type of questions that an interviewer might ask you during you interview for Java Programming. As a Fresher, you have either just attended an interview or planning to attend one soon. An Entry Level jobseeker looking to grow your career in software programming , you may be nervous about your upcoming interviews. All of us have those moments of panic where we blank out and might even forget what a thread is. We will simplify it for you, all you need to do it take a deep breath and check the questions that are most likely to be asked. You are confident and know you can handle anything the interviewer might throw at you.
What is the right data type to represent a price in Java? Answer: BigDecimal, if memory is not a concern and Performance, is not critical, otherwise double with predefined precision. What is a class in Java? Answer: Java encapsulates the codes in various classes which define new data types. These new data types are used to create objects. What is a JVM? Explain method overloading?
In this post, we will see Java interview questions for 5 to 6 years experience. When you have 5 years of experience as java developer, you need to have a good understanding of collections , multithreading concepts. Here are some questions which are most asked for 5 years of experience java programmers.
Follow along to brush up the most common advanced Java interview questions and answers that may win you a next job offer. Each Java source file is compiled into a bytecode file, which is executed by the JVM. Java was designed to allow application programs to be built that could be run on any platform, without having to be rewritten or recompiled by the programmer for each separate platform.
The main distinction between fail-fast and fail-safe iterators is whether or not the collection can be modified while it is being iterated. Fail-safe iterators allow this; fail-fast iterators do not.
Thanks for your comments guys, good to know that you like these programming interview questions and find useful. I suggest to contribute on this with some unique programming questions you faced during interviews. Thanks Javin. I was asked: How would you implement a queue using two stacks? Agree with you Anonymous, these programming questions can be very challenging to solve in limited time if faced first time. Nice questions you can include the following Write program to Reverse a string without using array.
There is the list of core Java interview questions. If there is any core Java interview question that has been asked to you, kindly post it in the ask question section. The answers to the Core Java interview questions are short and to the point. The core Java interview questions are categorized in Basics of Java interview questions, OOPs interview questions, String Handling interview questions, Multithreading interview questions, collection interview questions, JDBC interview questions, etc. Java is the high-level, object-oriented , robust, secure programming language, platform-independent, high performance, Multithreaded, and portable programming language. It was developed by James Gosling in June
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We have compiled the most frequently asked Java Interview Questions and Answers that will help you prepare for the Basic Java interview.
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Я хочу уйти. Стратмор глубоко вздохнул. Ясно, что без объяснений ему не обойтись. Она это заслужила, подумал он и принял решение: Сьюзан придется его выслушать. Он надеялся, что не совершает ошибку.
Срочно. Она попыталась собраться с мыслями.
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Can you please share a list of frequently asked Java programs on Interviews as well?