10 Interview Questions On Coffee Generics For Programmer Too Developers

Generic interview questions inwards Java interviews are getting to a greater extent than too to a greater extent than mutual alongside Java v only about at that spot for considerable fourth dimension too many application either moving to Java v too almost all novel Java evolution happening on Tiger(code mention of Java 5).  Importance of Generics too Java v features similar Enum,  Autoboxing, varargs too Collection utilities similar CountDownLatch, CyclicBarrier too BlockingQueue are getting to a greater extent than too to a greater extent than pop on Java interviews. Generic interview enquiry tin plough over the sack larn existent tricky if yous are non familiar alongside bounded too unbounded generic wildcards, How generics industrial plant internally, type erasure too familiarity alongside writing parametrized generics classes too methods inwards Java. Best means to prepare for Generics interview is to endeavor elementary plan best on diverse features of generics. Anyway In this Java interview article nosotros volition encounter some pop Java Generics interview questions too at that spot answer. By the means at that spot are lot of cloth available inwards to amend preparing for Java too J2EE interviews, yous tin plough over the sack prepare multi-threading too Collections using fifteen thread interview enquiry too Top 10 Java collection interview question along alongside several other questions answers articles on Spring, Struts, JSP too Servlet. If yous are GUI developers too working inwards Java Swing technology than yous tin plough over the sack likewise banking concern fit interview questions on Java Swing  generally asked inwards Investment banks

Java Generics Interview Questions

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

This is i of the kickoff interview questions asked on generics inwards whatsoever Java interview, generally at beginners too intermediate level. Those who are coming from prior to Java v background knows that how inconvenient it was to store object inwards Collection and hence cast it dorsum to right Type earlier using it. Generics prevents from those. it provides compile time type-safety too ensures that yous exclusively insert right Type inwards collection too avoids ClassCastException inwards runtime.

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

This is i of amend interview enquiry inwards Generics. Generics is implemented using Type erasure, compiler erases all type related information during compile fourth dimension too no type related information is available during runtime. for illustration List<String> is represented yesteryear exclusively at runtime. This was done to ensure binary compatibility alongside the libraries which were developed prior to Java 5. yous don't receive got access to Type declaration at runtime too Generic type is translated to Raw type yesteryear compiler during runtime. yous tin plough over the sack larn lot of follow upwardly enquiry based on this Generic interview enquiry based upon your response e.g. Why Generics is implemented using Type erasure or presenting some invalid generic code which results inwards compiler error. read my postal service How Generics industrial plant inwards Java for to a greater extent than details

3. What is Bounded too Unbounded wildcards inwards Generics ?

This is some other really popular Java interview questions on Generics. Bounded Wildcards are those which impose jump on Type. at that spot are 2 kinds of Bounded wildcards <? extends T> which impose an upper jump yesteryear ensuring that type must hold upwardly sub shape of T too <? super T> where its imposing lower jump yesteryear ensuring Type must hold upwardly super shape of T. This Generic Type must hold upwardly instantiated alongside Type inside jump otherwise it volition effect inwards compilation error. On the other manus <?> stand upwardly for too unbounded type because <?> tin plough over the sack hold upwardly supervene upon alongside whatsoever Type. See to a greater extent than on my postal service differences betwixt Bounded too Unbounded wildcards inwards Generics.

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

This is related to previous generics interview questions, some fourth dimension instead of shout for what is bounded too unbounded wildcards interviewer introduce this enquiry to estimate your agreement of generics. Both of List proclamation is example of bounded wildcards, List<? extends T> will receive got whatsoever List alongside Type extending T land List<? super T> volition receive got whatsoever List alongside type super shape of T. for Example List<? extends Number> can receive got List<Integer> or List<Float>. encounter to a greater extent than on inwards a higher house link.

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

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

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

6. How to write parametrized shape inwards Java using Generics ?

This is an extension of previous Java generics interview question. Instead of shout for to write Generic method Interviewer may enquire to write a type security shape using generics. i time to a greater extent than key is instead of using raw types yous demand to used generic types too ever role measure house holder used inwards JDK.

7. Write a plan to implement LRU cache using Generics ?

This is an practise for anyone who similar Coding inwards Java. One hint is that LinkedHashMap tin plough over the sack hold upwardly used implement fixed size LRU cache  where i needs to take away eldest entry when Cache is full. LinkedHashMap provides a method called removeEldestEntry() which is called yesteryear put() too putAll() too tin plough over the sack hold upwardly used to teach to take away eldest entry. yous are gratis to come upwardly up alongside your ain implementation equally long equally yous receive got a written a working version along alongside JUnit test.

8. Can yous top List<String> to a method which accepts List<Object>

This generic interview enquiry inwards Java may hold back confusing to whatsoever i who is non really familiar alongside Generics equally inwards fist glance it looks similar String is object hence List<String> can hold upwardly used where List<Object> is required but this is non true. It volition effect inwards compilation error. It does brand feel if yous larn i measurement farther because List<Object> tin plough over the sack shop whatsoever any affair including String, Integer etc but List<String> can exclusively shop Strings.

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

9. Can nosotros role Generics alongside Array?

This was in all likelihood most elementary generics interview enquiry inwards Java, if yous know the fact that Array doesn't back upwardly Generics too that's why Joshua Bloch suggested inwards Effective Java to prefer List over Array because List tin plough over the sack furnish compile fourth dimension type-safety over Array.

10. How tin plough over the sack yous suppress unchecked alarm inwards Java ?

javac compiler for Java v generates unchecked warnings if yous role combine raw types too generics types e.g.

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

which tin plough over the sack hold upwardly suppressed yesteryear using @SuppressWarnings("unchecked") annotation.

Java Generics Interview questions Update:

I got few to a greater extent than interview questions on Generics inwards Java to portion alongside yous guys, These questions focus on What is departure betwixt Generics type too Raw type too Can nosotros role Object inwards house of bounded wildcards etc:

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

Main departure betwixt raw type too parametrized type List<Object> is that, compiler will non banking concern fit type-safety of raw type at compile fourth dimension but it volition create that for parametrized type too yesteryear using Object equally Type it inform compiler that it tin plough over the sack concur whatsoever Type of Object e.g. String or Integer. This Java Generics interview enquiry is based on right agreement of  raw type inwards Generics. Any means minute departure betwixt them is that yous tin plough over the sack top whatsoever parametrized type to raw type List but yous tin plough over the sack non top List<String> to whatsoever method which receive got List<Object> it volition effect inwards compilation error. Read How Generics industrial plant inwards Java for to a greater extent than details.

Difference betwixt List<?> too List<Object> in Java?

This generics interview enquiry may hold back related to previous interview questions but completely different. List<?> is List of unknown type while List<Object> is essentially List of whatsoever Type. You tin plough over the sack assign List<String>, List<Integer> to List<?> but yous tin plough over the sack 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 near wildcards encounter Generics Wildcards Examples inwards Java

Difference betwixt List<String> too raw type List.

This Generics interview enquiry is similar to departure betwixt raw type too parametrized type.Parametrized type are type-safe too type-safety volition hold upwardly guaranteed yesteryear compiler but List raw type is non type safe. You tin plough over the sack non shop whatsoever other Object on List of String but yous tin plough over the sack non shop whatsoever Object inwards raw List. There is no casting required inwards instance of Parametrized type alongside Generics but explicit casting volition hold upwardly 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 plough over the sack non hold upwardly cast inwards String
     
List<String> listOfString = new ArrayList();
listOfString.add("abcd");
listOfString.add(1234); //compiler error, amend 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 too answers inwards Java. None of these generic interview questions are tough or hard, Indeed they are based on cardinal noesis of generics. Any Java programmer who has decent noesis of Generics must hold upwardly familiar alongside these generics questions inwards Java. If yous receive got whatsoever other proficient generic enquiry which has been asked inwards whatsoever interview or yous are looking reply for whatsoever Generics interview enquiry inwards Java hence delight postal service inwards comment section.

Further Learning
Introduction to Collections & Generics inwards Java
Java Fundamentals: Collections
Data Structures too Algorithms: Deep Dive Using Java

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