Interview Questions and Answers - Order By Newest        Q271.  What are meta Annotations ?  
Ans. Annotations that apply to other annotations are called meta-annotations.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   annotations   meta annotations  Q272.  Name few meta-annotations ?  
Ans. @Retention annotation specifies how the marked annotation is stored: @Documented annotation indicates that whenever the specified annotation is used those elements should be documented using the Javadoc tool. (By default, annotations are not included in Javadoc.)  @Target annotation marks another annotation to restrict what kind of Java elements the annotation can be applied to.  @Inherited annotation indicates that the annotation type can be inherited from the super class. (This is not true by default.) When the user queries the annotation type and the class has no annotation for this type, the class' superclass is queried for the annotation type. This annotation applies only to class declarations. @Repeatable annotation, introduced in Java SE 8, indicates that the marked annotation can be applied more than once to the same declaration or type use. For more information, see Repeating Annotations.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   java8   annotations   meta annotations  Q273.  How to display and set the Class path in Unix ?  
Ans. To display the current CLASSPATH variable, use these commands in UNIX (Bourne shell): % echo $CLASSPATH To delete the current contents of the CLASSPATH variable,  In UNIX:      % unset CLASSPATH; export CLASSPATH To set the CLASSPATH variable,  In UNIX:      % CLASSPATH=/home/george/java/classes; export CLASSPATH   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        unix   unix commands   classpath  Q274.  Different ways of implementing Threads in Java ?  Core Java 
Ans. Threads in Java can be implement either by Extending Thread class or implementing runnable interface.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   threads   multi threading      Asked in 1 Companies        basic          frequent Ans. A Method that cannot be overriden in the sub class.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   java keywords   final   final method   overriding   basic interview question       basic          frequent  Try 1 Question(s) TestVery Frequently asked.Favorite question in Walk in drive for many Indian service companies.   Q276.  What is a Final Class ?  
Ans. A Class that cannot be sub classed.    Sample Code for final class   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   final   final class   java keyword   basic interview question      Asked in 3 Companies        basic          frequent Very frequently asked. Usually asked with questions related to String. Frequently asked at CTS / Cognizant Ans. Object that can't be changed after instantiation.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   immutable  immutability      Asked in 27 Companies        basic          frequent  Try 2 Question(s) Test  Q278.  Does Declaring an object "final" makes it immutable ?  Core Java 
Ans. Only declaring variables as final makes them immutable. Making objects final means that the object handler cannot be used to target some other object but the object is still mutable.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   final   immutable  immutability   immutable  immutability object  Q279.  Can we override static methods ? Why ?  Core Java 
Ans. No.  Static methods belong to the class and not the objects. They belong to the class and hence doesn't fit properly for the polymorphic behavior.  A static method is not associated with any instance of a class so the concept of overriding for runtime polymorphism using static methods is not applicable.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   static   static methods   java keywords   yes-no       intermediate          frequent   Q280.  Can we reduce the visibility of the inherited or overridden method ?  Core Java 
Ans. No.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   access specifier   overriding   overridding   inheritence   yes-noAns. IndexOutofBoundException ,  
NoClassDefFoundException , 
OutOfMemoryException , 
IllegalArgumentException,  
NullPointerException,  
IllegalStateException   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   exceptions   basic interview question       basic          frequent   Q282.  How can we make sure that a code segment gets executed even in case of uncatched exceptions ?  
Ans. By putting it within finally.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   exceptions   finally   uncatched exceptions       basic          frequent   Q283.  What is "super" used for ?  
Ans. Used to access members of the base class.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   java keywords   super   basic interview question      Asked in 2 Companies        basic          frequent   Q284.  What is "this" keyword used for ?  
Ans. Used to represent an instance of the class in which it appears.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   java keywords   this   basic interview question       basic          frequent   Q285.  Difference between Serialization and Deserialization ?  Core Java 
Ans. Serialization is the process of writing the state of an object to a byte stream. Deserialization is the process of restoring these objects.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   oops   serialization   deserialization   serialization vs deserialization      Asked in 2 Companies        basic          frequent  Try 1 Question(s) TestAns. An enum type is a special data type that enables for a variable to be a set of predefined constants    Sample Code for enum   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   java5   enum   basic interview question       basic          frequent  Try 2 Question(s) Test  Q287.  What are Wrapper Classes ? What are Primitive Wrapper Classes ?  Core Java 
Ans. A wrapper class is any class which "wraps" or "encapsulates" the functionality of another class or component. A Wrapper Class that wraps or encapsulates the primitive data type is called Primitive Wrapper Class.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   wrapper classes   primitive wrapper classes  Q288.  What Design pattern Wrapper Classes implement ?  Design 
Ans. Adapter.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   wrapper classes   adapter design pattern   design patternAns. Enables the programmer to abbreviate the names of classes defined in a package.    Sample Code for import   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   import   java keyword  Q290.  Different types of memory used by JVM ?  Core Java 
Ans. Class , Heap , Stack , Register , Native Method Stack.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   jvm   memory management   memory   advanced   architecture   technical architect      Asked in 1 Companies        intermediate          frequent  Try 5 Question(s) Test  Q291.  What is a class loader ? What are the different class loaders used by JVM ?  Core Java 
Ans. Part of JVM which is used to load classes and interfaces. 
 
Bootstrap , Extension and System are the class loaders used by JVM.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   class loaders  classloaders   jvm   java memory management   advanced      Asked in 3 Companies Ans. By static import , we can access the static members of a class directly without prefixing it with the class name.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   java5   static import   static   java keyword   static import      Asked in 4 Companies        basic          frequent   Q293.  Difference between Map and HashMap ?  Core Java 
Ans. Map is an interface where HashMap is the concrete class.    Sample Code for map    Sample Code for hashmap   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   collections   hashmap   map       basic          frequent Ans. The properties class is a subclass of Hashtable that can be read from or written to a stream.    Sample Code for Load Properties using Property Class   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   collections   hashtable   map   synchronization   synchronized  Q295.  Can we have multiple servlets in a web application and How can we do that ?  Java EE 
Ans. Yes by making entries in web.xml   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        j2ee   servlets   servelets   web application   java   web.xml   yes-no   architecture  Q296.  How can we manage Error Messages in the web application ?  Solution 
Ans. Within message.properties file.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        j2ee   web application   struts   spring      Asked in 1 Companies Frequently asked to fresh graduates.   Q297.  Is JVM, a compiler or interpretor ?  
Ans. Its an interpretor.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   jvm   compiler   interpretor       basic          frequent   Q298.  Difference between Proxy and Adapter ?  Design 
Ans. Adapter object has a different input than the real subject whereas Proxy object has the same input as the real subject. Proxy object is such that it should be placed as it is in place of the real subject.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   design pattern   proxy   adapter   proxy vs adapter       expert   Q299.  Difference between Adapter and Facade ?  Design 
Ans. The Difference between these patterns in only the intent. Adapter is used because the objects in current form cannot communicate where as in Facade , though the objects can communicate , A Facade object is placed between the client and subject to simplify the interface.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   design pattern   adapter   facade       expert   Q300.  Example of Chain of Responsibility Design Pattern ?  
Ans. Exception Handling Throw mechanism.   Help us improve. Please let us know the company, where you were asked this question   :       Like            Discuss            Correct / Improve        java   design pattern   chain of responsibility       expert