10 Interview Questions On Coffee Generics For Programmer In Addition To Developers

Generic interview questions inward Java interviews are getting to a greater extent than in addition to to a greater extent than mutual amongst Java v roughly at that topographic point for considerable fourth dimension in addition to many application either moving to Java v in addition to almost all novel Java evolution happening on Tiger(code refer of Java 5).  Importance of Generics in addition to Java v features similar Enum,  Autoboxing, varargs in addition to Collection utilities similar CountDownLatch, CyclicBarrier in addition to BlockingQueue are getting to a greater extent than in addition to to a greater extent than pop on Java interviews. Generic interview query tin larn existent tricky if you lot are non familiar amongst bounded in addition to unbounded generic wildcards, How generics industrial plant internally, type erasure in addition to familiarity amongst writing parametrized generics classes in addition to methods inward Java. Best means to prepare for Generics interview is to effort uncomplicated computer program best on diverse features of generics. Anyway In this Java interview article nosotros volition come across some pop Java Generics interview questions in addition to at that topographic point answer. By the means at that topographic point are lot of cloth available inward to ameliorate preparing for Java in addition to J2EE interviews, you lot tin prepare multi-threading in addition to Collections using xv thread interview query in addition to Top 10 Java collection interview question along amongst several other questions answers articles on Spring, Struts, JSP in addition to Servlet. If you lot are GUI developers in addition to working inward Java Swing technology scientific discipline than you lot tin likewise cheque interview questions on Java Swing  generally asked inward Investment banks

Java Generics Interview Questions

1. What is Generics inward Java ? What are advantages of using Generics?

This is ane of the offset interview questions asked on generics inward whatever Java interview, generally at beginners in addition to intermediate level. Those who are coming from prior to Java v background knows that how inconvenient it was to store object inward Collection and in addition to hence cast it dorsum to right Type earlier using it. Generics prevents from those. it provides compile time type-safety in addition to ensures that you lot alone insert right Type inward collection in addition to avoids ClassCastException inward runtime.

2. How Generics industrial plant inward Java ? What is type erasure ?

This is ane of ameliorate interview query inward Generics. Generics is implemented using Type erasure, compiler erases all type related information during compile fourth dimension in addition to no type related information is available during runtime. for illustration List<String> is represented past times alone at runtime. This was done to ensure binary compatibility amongst the libraries which were developed prior to Java 5. you lot don't receive got access to Type declaration at runtime in addition to Generic type is translated to Raw type past times compiler during runtime. you lot tin larn lot of follow upwards query based on this Generic interview query based upon your response e.g. Why Generics is implemented using Type erasure or presenting some invalid generic code which results inward compiler error. read my transportation service How Generics industrial plant inward Java for to a greater extent than details

3. What is Bounded in addition to Unbounded wildcards inward Generics ?

This is some other really popular Java interview questions on Generics. Bounded Wildcards are those which impose jump on Type. at that topographic point are 2 kinds of Bounded wildcards <? extends T> which impose an upper jump past times ensuring that type must hold upwards sub bird of T in addition to <? super T> where its imposing lower jump past times ensuring Type must hold upwards super bird of T. This Generic Type must hold upwards instantiated amongst Type inside jump otherwise it volition effect inward compilation error. On the other mitt <?> stand upwards for in addition to unbounded type because <?> tin hold upwards supersede amongst whatever Type. See to a greater extent than on my transportation service differences betwixt Bounded in addition to Unbounded wildcards inward Generics.

4. What is divergence betwixt List<? extends T>  and  List <? super T> ?

This is related to previous generics interview questions, some fourth dimension instead of quest what is bounded in addition to unbounded wildcards interviewer introduce this query to estimate your agreement of generics. Both of List annunciation is example of bounded wildcards, List<? extends T> will convey whatever List amongst Type extending T spell List<? super T> volition convey whatever List amongst type super bird of T. for Example List<? extends Number> can convey List<Integer> or List<Float>. come across to a greater extent than on to a higher house link.

5. How to write a generic method which accepts generic declaration in addition to render Generic Type?

Java Collection framework for examples of generics methods. In simplest shape a generic method would await like:

public V put(K key, V value) {
        return cache.put(key, value);
}

6. How to write parametrized bird inward Java using Generics ?

This is an extension of previous Java generics interview question. Instead of quest to write Generic method Interviewer may enquire to write a type prophylactic bird using generics. ane time again key is instead of using raw types you lot demand to used generic types in addition to e'er purpose measure house holder used inward JDK.

7. Write a computer program to implement LRU cache using Generics ?

This is an do for anyone who similar Coding inward Java. One hint is that LinkedHashMap tin hold upwards used implement fixed size LRU cache  where ane needs to take away eldest entry when Cache is full. LinkedHashMap provides a method called removeEldestEntry() which is called past times put() in addition to putAll() in addition to tin hold upwards used to learn to take away eldest entry. you lot are complimentary to come upwards up amongst your ain implementation every bit long every bit you lot receive got a written a working version along amongst JUnit test.

8. Can you lot exceed List<String> to a method which accepts List<Object>

This generic interview query inward Java may await confusing to whatever ane who is non really familiar amongst Generics every bit inward fist glance it looks similar String is object hence List<String> can hold upwards used where List<Object> is required simply this is non true. It volition effect inward compilation error. It does brand feel if you lot become ane measuring farther because List<Object> tin shop whatever any matter including String, Integer etc simply List<String> can alone shop Strings.

List<Object> objectList;
List<String> stringList;
     
objectList = stringList;  //compilation mistake incompatible types

9. Can nosotros purpose Generics amongst Array?

This was in all likelihood most uncomplicated generics interview query inward Java, if you lot know the fact that Array doesn't back upwards Generics in addition to that's why Joshua Bloch suggested inward Effective Java to prefer List over Array because List tin furnish compile fourth dimension type-safety over Array.

10. How tin you lot suppress unchecked alarm inward Java ?

javac compiler for Java v generates unchecked warnings if you lot purpose combine raw types in addition to generics types e.g.

List<String> rawList = new ArrayList()
Note: Hello.java uses unchecked or dangerous operations.;

which tin hold upwards suppressed past times using @SuppressWarnings("unchecked") annotation.

Java Generics Interview questions Update:

I got few to a greater extent than interview questions on Generics inward Java to percentage amongst you lot guys, These questions focus on What is divergence betwixt Generics type in addition to Raw type in addition to Can nosotros purpose Object inward house of bounded wildcards etc:

Difference betwixt List<Object> and raw type List inward Java?

Main divergence betwixt raw type in addition to parametrized type List<Object> is that, compiler will non cheque type-safety of raw type at compile fourth dimension simply it volition produce that for parametrized type in addition to past times using Object every bit Type it inform compiler that it tin concur whatever Type of Object e.g. String or Integer. This Java Generics interview query is based on right agreement of  raw type inward Generics. Any means minute divergence betwixt them is that you lot tin exceed whatever parametrized type to raw type List simply you lot tin non exceed List<String> to whatever method which convey List<Object> it volition effect inward compilation error. Read How Generics industrial plant inward Java for to a greater extent than details.

Difference betwixt List<?> in addition to List<Object> in Java?

This generics interview query may await related to previous interview questions simply completely different. List<?> is List of unknown type while List<Object> is essentially List of whatever Type. You tin assign List<String>, List<Integer> to List<?> simply you lot tin non assign List<String> to List<Object>.

List<?> listOfAnyType;
List<Object> listOfObject = new ArrayList<Object>();
List<String> listOfString = new ArrayList<String>();
List<Integer> listOfInteger = new ArrayList<Integer>();
     
listOfAnyType = listOfString; //legal
listOfAnyType = listOfInteger; //legal
listOfObjectType = (List<Object>) listOfString; //compiler mistake - in-convertible types

            

to know to a greater extent than virtually wildcards come across Generics Wildcards Examples inward Java

Difference betwixt List<String> in addition to raw type List.

This Generics interview query is similar to divergence betwixt raw type in addition to parametrized type.Parametrized type are type-safe in addition to type-safety volition hold upwards guaranteed past times compiler simply List raw type is non type safe. You tin non shop whatever other Object on List of String simply you lot tin non shop whatever Object inward raw List. There is no casting required inward instance of Parametrized type amongst Generics simply explicit casting volition hold upwards needed for raw type.

List listOfRawTypes = new ArrayList();
listOfRawTypes.add("abc");
listOfRawTypes.add(123); //compiler volition allow this - exception at runtime
String item = (String) listOfRawTypes.get(0); //explicit cast is required
item = (String) listOfRawTypes.get(1); //ClassCastException because Integer tin non hold upwards cast inward String
     
List<String> listOfString = new ArrayList();
listOfString.add("abcd");
listOfString.add(1234); //compiler error, ameliorate than runtime Exception
item = listOfString.get(0); //no explicit casting is required - compiler auto cast

These were some of the frequently asked generics interview questions in addition to answers inward Java. None of these generic interview questions are tough or hard, Indeed they are based on cardinal cognition of generics. Any Java programmer who has decent cognition of Generics must hold upwards familiar amongst these generics questions inward Java. If you lot receive got whatever other expert generic query which has been asked inward whatever interview or you lot are looking respond for whatever Generics interview query inward Java in addition to hence delight transportation service inward comment section.

Further Learning
Introduction to Collections & Generics inward Java
Java Fundamentals: Collections
Data Structures in addition to Algorithms: Deep Dive Using Java

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