Spring MVC Framework Some Java Collections Interview Questions Part - 2


Q: What is Java Collections API?

Java Collections framework API is a unified architecture for representing and manipulating collections. The API contains Interfaces, Implementations & Algorithm to help java programmer in everyday programming. In nutshell, this API does 6 things at high level

  • Reduces programming efforts. - Increases program speed and quality.
  • Allows interoperability among unrelated APIs.
  • Reduces effort to learn and to use new APIs.
  • Reduces effort to design new APIs.
  • Encourages & Fosters software reuse.

To be specific, There are six collection java interfaces. The most basic interface is Collection. Three interfaces extend Collection: Set, List, and SortedSet. The other two collection interfaces, Map and SortedMap, do not extend Collection, as they represent mappings rather than true collections.

Q: What is an Iterator?

Some of the collection classes provide traversal of their contents via a java.util.Iterator interface. This interface allows you to walk through a collection of objects, operating on each object in turn. Remember when using Iterators that they contain a snapshot of the collection at the time the Iterator was obtained; generally it is not advisable to modify the collection itself while traversing an Iterator.

Q: What is the difference between java.util.Iterator and java.util.ListIterator?


  • Iterator : Enables you to traverse through a collection in the forward direction only, for obtaining or removing elements. 
  • ListIterator : extends Iterator, and allows bidirectional traversal of list and also allows the modification of elements.


Q: What is HashMap and Map?

Map is Interface which is part of Java collections framework. This is to store Key Value pair, and Hashmap is class that implements that using hashing technique.

Q: Difference between HashMap and HashTable? Compare Hashtable vs HashMap?

Both Hashtable & HashMap provide key-value access to data. The Hashtable is one of the original collection classes in Java (also called as legacy classes). HashMap is part of the new Collections Framework, added with Java 2, v1.2. There are several differences between HashMap and Hashtable in Java as listed below

  • The HashMap class is roughly equivalent to Hashtable, except that it is unsynchronized and permits nulls. (HashMap allows null values as key and value whereas Hashtable doesn’t allow nulls).
  • HashMap does not guarantee that the order of the map will remain constant over time. But one of HashMap's subclasses is LinkedHashMap, so in the event that you'd want predictable iteration order (which is insertion order by default), you can easily swap out the HashMap for a LinkedHashMap. This wouldn't be as easy if you were using Hashtable.
  • HashMap is non synchronized whereas Hashtable is synchronized.
  • Iterator in the HashMap is fail-fast while the enumerator for the Hashtable isn't. So this could be a design consideration.


Q: What does synchronized means in Hashtable context?

Synchronized means only one thread can modify a hash table at one point of time. Any thread before performing an update on a hashtable will have to acquire a lock on the object while others will wait for lock to be released.

Q: What is fail-fast property?


At high level - Fail-fast is a property of a system or software with respect to its response to failures. A fail-fast system is designed to immediately report any failure or condition that is likely to lead to failure. Fail-fast systems are usually designed to stop normal operation rather than attempt to continue a possibly-flawed process. When a problem occurs, a fail-fast system fails immediately and visibly. Failing fast is a non-intuitive technique: "failing immediately and visibly" sounds like it would make your software more fragile, but it actually makes it more robust. Bugs are easier to find and fix, so fewer go into production. In Java, Fail-fast term can be related to context of iterators. If an iterator has been created on a collection object and some other thread tries to modify the collection object "structurally", a concurrent modification exception will be thrown. It is possible for other threads though to invoke "set" method since it doesn't modify the collection "structurally". However, if prior to calling "set", the collection has been modified structurally, "IllegalArgumentException" will be thrown.

Q: Why doesn't Collection extend Cloneable and Serializable?


From Sun FAQ Page: Many Collection implementations (including all of the ones provided by the JDK) will have a public clone method, but it would be mistake to require it of all Collections. For example, what does it mean to clone a Collection that's backed by a terabyte SQL database? Should the method call cause the company to requisition a new disk farm? Similar arguments hold for serializable. If the client doesn't know the actual type of a Collection, it's much more flexible and less error prone to have the client decide what type of Collection is desired, create an empty Collection of this type, and use the addAll method to copy the elements of the original collection into the new one. Note on Some Important Terms

  • Synchronized means only one thread can modify a hash table at one point of time. Basically, it means that any thread before performing an update on a hashtable will have to acquire a lock on the object while others will wait for lock to be released.
  • Fail-fast is relevant from the context of iterators. If an iterator has been created on a collection object and some other thread tries to modify the collection object "structurally”, a concurrent modification exception will be thrown. It is possible for other threads though to invoke "set" method since it doesn’t modify the collection "structurally”. However, if prior to calling "set", the collection has been modified structurally, "IllegalArgumentException" will be thrown.


Q: How can we make Hashmap synchronized?


HashMap can be synchronized by Map m = Collections.synchronizedMap(hashMap);

Q: Where will you use Hashtable and where will you use HashMap?


There are multiple aspects to this decision: 1. The basic difference between a Hashtable and an HashMap is that, Hashtable is synchronized while HashMap is not. Thus whenever there is a possibility of multiple threads accessing the same instance, one should use Hashtable. While if not multiple threads are going to access the same instance then use HashMap. Non synchronized data structure will give better performance than the synchronized one. 2. If there is a possibility in future that - there can be a scenario when you may require to retain the order of objects in the Collection with key-value pair then HashMap can be a good choice. As one of HashMap's subclasses is LinkedHashMap, so in the event that you'd want predictable iteration order (which is insertion order by default), you can easily swap out the HashMap for a LinkedHashMap. This wouldn't be as easy if you were using Hashtable. Also if you have multiple thread accessing you HashMap then Collections.synchronizedMap() method can be leveraged. Overall HashMap gives you more flexibility in terms of possible future changes.

Q: Difference between Vector and ArrayList? What is the Vector class?


Vector & ArrayList both classes are implemented using dynamically resizable arrays, providing fast random access and fast traversal. ArrayList and Vector class both implement the List interface. Both the classes are member of Java collection framework, therefore from an API perspective, these two classes are very similar. However, there are still some major differences between the two. Below are some key differences

  • Vector is a legacy class which has been retrofitted to implement the List interface since Java 2 platform v1.2
  • Vector is synchronized whereas ArrayList is not. Even though Vector class is synchronized, still when you want programs to run in multithreading environment using ArrayList with Collections.synchronizedList() is recommended over Vector.
  • ArrayList has no default size while vector has a default size of 10.
  • The Enumerations returned by Vector's elements method are not fail-fast. Whereas ArraayList does not have any method returning Enumerations.


Q: What is the Difference between Enumeration and Iterator interface?


Enumeration and Iterator are the interface available in java.util package. The functionality of Enumeration interface is duplicated by the Iterator interface. New implementations should consider using Iterator in preference to Enumeration. Iterators differ from enumerations in following ways:

  1. Enumeration contains 2 methods namely hasMoreElements() & nextElement() whereas Iterator contains three methods namely hasNext(), next(),remove().
  2. Iterator adds an optional remove operation, and has shorter method names. Using remove() we can delete the objects but Enumeration interface does not support this feature.
  3. Enumeration interface is used by legacy classes. Vector.elements() & Hashtable.elements() method returns Enumeration. Iterator is returned by all Java Collections Framework classes. java.util.Collection.iterator() method returns an instance of Iterator.


Q: Why Java Vector class is considered obsolete or unofficially deprecated? or Why should I always use ArrayList over Vector?


You should use ArrayList over Vector because you should default to non-synchronized access. Vector synchronizes each individual method. That's almost never what you want to do. Generally you want to synchronize a whole sequence of operations. Synchronizing individual operations is both less safe (if you iterate over a Vector, for instance, you still need to take out a lock to avoid anyone else changing the collection at the same time) but also slower (why take out a lock repeatedly when once will be enough)? Of course, it also has the overhead of locking even when you don't need to. It's a very flawed approach to have synchronized access as default. You can always decorate a collection using Collections.synchronizedList - the fact that Vector combines both the "resized array" collection implementation with the "synchronize every operation" bit is another example of poor design; the decoration approach gives cleaner separation of concerns. Vector also has a few legacy methods around enumeration and element retrieval which are different than the List interface, and developers (especially those who learned Java before 1.2) can tend to use them if they are in the code. Although Enumerations are faster, they don't check if the collection was modified during iteration, which can cause issues, and given that Vector might be chosen for its syncronization - with the attendant access from multiple threads, this makes it a particularly pernicious problem. Usage of these methods also couples a lot of code to Vector, such that it won't be easy to replace it with a different List implementation. Despite all above reasons Sun may never officially deprecate Vector class. (Read details Deprecate Hashtable and Vector)

Q: What is an enumeration?

An enumeration is an interface containing methods for accessing the underlying data structure from which the enumeration is obtained. It is a construct which collection classes return when you request a collection of all the objects stored in the collection. It allows sequential access to all the elements stored in the collection.

Q: What is the difference between Enumeration and Iterator?


The functionality of Enumeration interface is duplicated by the Iterator interface. Iterator has a remove() method while Enumeration doesn't. Enumeration acts as Read-only interface, because it has the methods only to traverse and fetch the objects, where as using Iterator we can manipulate the objects also like adding and removing the objects. So Enumeration is used when ever we want to make Collection objects as Read-only.

Q: Where will you use Vector and where will you use ArrayList?


The basic difference between a Vector and an ArrayList is that, vector is synchronized while ArrayList is not. Thus whenever there is a possibility of multiple threads accessing the same instance, one should use Vector. While if not multiple threads are going to access the same instance then use ArrayList. Non synchronized data structure will give better performance than the synchronized one.

Q: What is the importance of hashCode() and equals() methods? How they are used in Java?



The java.lang.Object has two methods defined in it. They are - public boolean equals(Object obj) public int hashCode(). These two methods are used heavily when objects are stored in collections. There is a contract between these two methods which should be kept in mind while overriding any of these methods. The Java API documentation describes it in detail. The hashCode() method returns a hash code value for the object. This method is supported for the benefit of hashtables such as those provided by java.util.Hashtable or java.util.HashMap. The general contract of hashCode is: Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application. If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result. It is not required that if two objects are unequal according to the equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hashtables. As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. The equals(Object obj) method indicates whether some other object is "equal to" this one. The equals method implements an equivalence relation on non-null object references: It is reflexive: for any non-null reference value x, x.equals(x) should return true. It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true. It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true. It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified. For any non-null reference value x, x.equals(null) should return false. The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true). Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes. A practical Example of hashcode() & equals(): This can be applied to classes that need to be stored in Set collections. Sets use equals() to enforce non-duplicates, and HashSet uses hashCode() as a first-cut test for equality. Technically hashCode() isn't necessary then since equals() will always be used in the end, but providing a meaningful hashCode() will improve performance for very large sets or objects that take a long time to compare using equals().

Q: What is the difference between Sorting performance of Arrays.sort() vs Collections.sort() ? Which one is faster? Which one to use and when?


Many developers are concerned about the performance difference between java.util.Array.sort() java.util.Collections.sort() methods. Both methods have same algorithm the only difference is type of input to them. Collections.sort() has a input as List so it does a translation of List to array and vice versa which is an additional step while sorting. So this should be used when you are trying to sort a list. Arrays.sort is for arrays so the sorting is done directly on the array. So clearly it should be used when you have a array available with you and you want to sort it.

Q: What is java.util.concurrent BlockingQueue? How it can be used?


Java has implementation of BlockingQueue available since Java 1.5. Blocking Queue interface extends collection interface, which provides you power of collections inside a queue. Blocking Queue is a type of Queue that additionally supports operations that wait for the queue to become non-empty when retrieving an element, and wait for space to become available in the queue when storing an element. A typical usage example would be based on a producer-consumer scenario. Note that a BlockingQueue can safely be used with multiple producers and multiple consumers. An ArrayBlockingQueue is a implementation of blocking queue with an array used to store the queued objects. The head of the queue is that element that has been on the queue the longest time. The tail of the queue is that element that has been on the queue the shortest time. New elements are inserted at the tail of the queue, and the queue retrieval operations obtain elements at the head of the queue. ArrayBlockingQueue requires you to specify the capacity of queue at the object construction time itself. Once created, the capacity cannot be increased. This is a classic "bounded buffer" (fixed size buffer), in which a fixed-sized array holds elements inserted by producers and extracted by consumers. Attempts to put an element to a full queue will result in the put operation blocking; attempts to retrieve an element from an empty queue will be blocked.

Q: Set & List interface extend Collection, so Why doesn't Map interface extend Collection?



Though the Map interface is part of collections framework, it does not extend collection interface. This is by design, and the answer to this questions is best described in Sun's FAQ Page: This was by design. We feel that mappings are not collections and collections are not mappings. Thus, it makes little sense for Map to extend the Collection interface (or vice versa). If a Map is a Collection, what are the elements? The only reasonable answer is "Key-value pairs", but this provides a very limited (and not particularly useful) Map abstraction. You can't ask what value a given key maps to, nor can you delete the entry for a given key without knowing what value it maps to. Collection could be made to extend Map, but this raises the question: what are the keys? There's no really satisfactory answer, and forcing one leads to an unnatural interface. Maps can be viewed as Collections (of keys, values, or pairs), and this fact is reflected in the three "Collection view operations" on Maps (keySet, entrySet, and values). While it is, in principle, possible to view a List as a Map mapping indices to elements, this has the nasty property that deleting an element from the List changes the Key associated with every element before the deleted element. That's why we don't have a map view operation on Lists.

Q: Which implementation of the List interface provides for the fastest insertion of a new element into the middle of the list?



a. Vector b. ArrayList c. LinkedList ArrayList and Vector both use an array to store the elements of the list. When an element is inserted into the middle of the list the elements that follow the insertion point must be shifted to make room for the new element. The LinkedList is implemented using a doubly linked list; an insertion requires only the updating of the links at the point of insertion. Therefore, the LinkedList allows for fast insertions and deletions.

Q: What is the difference between ArrayList and LinkedList? (ArrayList vs LinkedList.)


java.util.ArrayList and java.util.LinkedList are two Collections classes used for storing lists of object references Here are some key differences:

  • ArrayList uses primitive object array for storing objects whereas LinkedList is made up of a chain of nodes. Each node stores an element and the pointer to the next node. A singly linked list only has pointers to next. A doubly linked list has a pointer to the next and the previous element. This makes walking the list backward easier.
  • ArrayList implements the RandomAccess interface, and LinkedList does not. The commonly used ArrayList implementation uses primitive Object array for internal storage. Therefore an ArrayList is much faster than a LinkedList for random access, that is, when accessing arbitrary list elements using the get method. Note that the get method is implemented for LinkedLists, but it requires a sequential scan from the front or back of the list. This scan is very slow. For a LinkedList, there's no fast way to access the Nth element of the list.
  • Adding and deleting at the start and middle of the ArrayList is slow, because all the later elements have to be copied forward or backward. (Using System.arrayCopy()) Whereas Linked lists are faster for inserts and deletes anywhere in the list, since all you do is update a few next and previous pointers of a node.
  • Each element of a linked list (especially a doubly linked list) uses a bit more memory than its equivalent in array list, due to the need for next and previous pointers.
  • ArrayList may also have a performance issue when the internal array fills up. The arrayList has to create a new array and copy all the elements there. The ArrayList has a growth algorithm of (n*3)/2+1, meaning that each time the buffer is too small it will create a new one of size (n*3)/2+1 where n is the number of elements of the current buffer. Hence if we can guess the number of elements that we are going to have, then it makes sense to create a arraylist with that capacity during object creation (using construtor new ArrayList(capacity)). Whereas LinkedLists should not have such capacity issues.


Q: Where will you use ArrayList and Where will you use LinkedList? Or Which one to use when (ArrayList / LinkedList).


Below is a snippet from SUN's site. The Java SDK contains 2 implementations of the List interface - ArrayList and LinkedList. If you frequently add elements to the beginning of the List or iterate over the List to delete elements from its interior, you should consider using LinkedList. These operations require constant-time in a LinkedList and linear-time in an ArrayList. But you pay a big price in performance. Positional access requires linear-time in a LinkedList and constant-time in an ArrayList.

Q: What is performance of various Java collection implementations/algorithms? What is Big 'O' notation for each of them ?


Each java collection implementation class have different performance for different methods, which makes them suitable for different programming needs.

Performance of Map interface implementations


  • Hashtable : An instance of Hashtable has two parameters that affect its performance: initial capacity and load factor. The capacity is the number of buckets in the hash table, and the initial capacity is simply the capacity at the time the hash table is created. Note that the hash table is open: in the case of a "hash collision", a single bucket stores multiple entries, which must be searched sequentially. The load factor is a measure of how full the hash table is allowed to get before its capacity is automatically increased. The initial capacity and load factor parameters are merely hints to the implementation. The exact details as to when and whether the rehash method is invoked are implementation-dependent.
  • HashMap : This implementation provides constant-time [ Big O Notation is O(1) ] performance for the basic operations (get and put), assuming the hash function disperses the elements properly among the buckets. Iteration over collection views requires time proportional to the "capacity" of the HashMap instance (the number of buckets) plus its size (the number of key-value mappings). Thus, it's very important not to set the initial capacity too high (or the load factor too low) if iteration performance is important.
  • TreeMap : The TreeMap implementation provides guaranteed log(n) [ Big O Notation is O(log N) ] time cost for the containsKey, get, put and remove operations.
  • LinkedHashMap : A linked hash map has two parameters that affect its performance: initial capacity and load factor. They are defined precisely as for HashMap. Note, however, that the penalty for choosing an excessively high value for initial capacity is less severe for this class than for HashMap, as iteration times for this class are unaffected by capacity.


Performance of Set interface implementations



  • HashSet : The HashSet class offers constant-time [ Big O Notation is O(1) ] performance for the basic operations (add, remove, contains and size), assuming the hash function disperses the elements properly among the buckets. Iterating over this set requires time proportional to the sum of the HashSet instance's size (the number of elements) plus the "capacity" of the backing HashMap instance (the number of buckets). Thus, it's very important not to set the initial capacity too high (or the load factor too low) if iteration performance is important.
  • TreeSet : The TreeSet implementation provides guaranteed log(n) time cost for the basic operations (add, remove and contains).
  • LinkedHashSet : A linked hash set has two parameters that affect its performance: initial capacity and load factor. They are defined precisely as for HashSet. Note, however, that the penalty for choosing an excessively high value for initial capacity is less severe for this class than for HashSet, as iteration times for this class are unaffected by capacity.

Performance of List interface implementations

LinkedList : Performance of get and remove methods is linear time [ Big O Notation is O(n) ] - Performance of add and Iterator.remove methods is constant-time [ Big O Notation is O(1) ]
ArrayList : The size, isEmpty, get, set, iterator, and listIterator operations run in constant time. [ Big O Notation is O(1) ] - The add operation runs in amortized constant time [ Big O Notation is O(1) ] , but in worst case (since the array must be resized and copied) adding n elements requires linear time [ Big O Notation is O(n) ] - Performance of remove method is linear time [ Big O Notation is O(n) ] - All of the other operations run in linear time [ Big O Notation is O(n) ]. The constant factor is low compared to that for the LinkedList implementation.

Labels

.equals = operator abstract class abstract method abstract window toolkit Access Modifiers accessing java beans accessing javabeans action events actionperformed active addition Advanced Advanced Overloading AdvJavaBooks Agile development ajax alive AMQP and Android anonymous class anonymous inner class Ant ant tutorials anti patterns antipatterns Apache Camel api for jsp api for servlet api for servlets api jsp application context application scope application session Apps Architecture are you eligible for the ocmjd certificaiton are you eligible for the scjd certification arithmetic operator arpanet array construction array declaration array initialization array list array to list conversion arraylist arraylist of strings arraylist of types arraylist questions arraylists Arrays arrays in java ask for help assert assert in java assertions assertions in java assignment assignment operator Atlassian attribute visibility authentication authorization autoboxing autounboxing awt AWT Event Handling awt interview questions AWT Layouts awt questions awt questions and answers backed collection backed collections Basic Basics of event handling bean attributes bean properties bean scope Beginner best practices BigData blocked books boxing buffer size bufferedreader bufferedwriter business delegate business delegate pattern calendar case statement casting in java casting interview questions chapter review choosing a java locking mechanism choosing a locking mechanism choosing a thread locking mechanism class inside a method class questions class with no name class without a name classes interview questions Clipboard closing jsp tags code snap coding cohesion collection generics collection interview questions collection methods collection of types collection questions collection searching collection types Collections Collections Framework collections interview questions collections sorting colors in java swings colors in swing command line arguments communication between threads comparable comparator comparison operators compiling java classes computers concurrency example and tutorial config Configuration ConnectionPooling constructor creation constructor interview questions constructor overloading constructors in java containers contents of deployment descriptor contents of web.xml context context scope converting array to list converting list to array core java core java interview core java interview question core java interview questions core java questions core java; core java; object oriented programming CoreJava CoreJavaBooks CORS coupling create threads creating 2 dimensional shapes creating 2D shapes creating a frame creating a jframe creating a thread creating an arraylist creating an inner class creating an interface creating java beans creating java threads creating javabeans creating threads creating threads in java CSS cURL currency current thread determination custom tag library custom taglib custom taglibs custom tags CVS dao dao design pattern dao factory pattern dao pattern data access object data access object pattern data structure and algorithm database date and time tutorial date format dateformat dates deadlock deadlocks debugging Declarations decorator pattern decrement default deleting sessions deploy web app deployment deployment descriptor deployment descriptor contents deployment of web application deserialization deserialize design pattern design pattern interview questions design patterns Designpatterns destory method destroy destroying sessions determining current thread determining the current thread Developer Differences different types of collections display stuff in a frame displaying images displaying images in java swings displaying images in swings displaying text in a component division do while loop doget dohead dopost doput DOS Downloads drawing a line drawing an ellipse drawing circles drawing ellipses drawing lines Drools tutorial eBooks Eclipse Eclipse Tutorial Encapsulation encapsulation in java enhanced for loop entity facade pattern enumerations enumerations in java enums equal to equals equals comparison error and exception error codes error handling in servlets error page event handling in swings event listeners exam prep tips example servlet Examples exception exception handling exception handling in servlets exception handling interview questions exception handling questions Exceptions exceptions in java exceptions in web applications explicit locking explicit locking of objects file file navigation filereader filewriter final class final method FireBug first servlet FIX protocol FIX Protocol interview questions FIX protocol tutorial font fonts for each loop for loop form parameters form values formatting forwarding requests frame frame creation frame positioning frame swings front controller front controller design pattern front controller pattern fundamental.Java FXML Games garbage collection garbage collection interview questions garbage collection questions garbage collector gc gc questions general generic Generics generics collections Geo get get set methods getattribute getting bean property getting form values getting form values in servlet getting scwcd certified getting servlet initialization parameters getting sun certified Google Graphics2D gregorian calendar handling strings in java hash hash map hash table hashcode hashmap hashset hashtable head head request HeadFirst heap heaps hibernate hibernate interview questions hibernate interview questions and answers hibernate questions hibernate questions and answers Hibernate Tutorial HibernateBooks homework How To HTML HTML and JavaScript html form http request http request handling http request header http request methods http request servlet http request type http session httprequest httprequest methods httpservlet httpservlet interview questions httpservlet interview questions with answers httpsession httpsession interview questions httpsession questions HttpSessionActivationListener HttpSessionAttributeListener HttpSessionBindingListener if if else if else block if else statement Image IO implementing an interface Implicit objects increment info inheritance inheritance in java init init method Initialization Blocks inner class inner class inside a method inner classes innerclass installation instanceof instanceof operator IntelliJ interaction between threads interface interface interview interface questions interfaces interfaces in java interfaces interview questions internet history interrupting a thread interrupting threads Interview interview questions interview questions on design patterns interview questions on exception handling interview questions on java collections interview questions on serialization introduction to java threads introduction to jsps introduction to threading introduction to threads invalidating session Investment Banking IO Package iscurrentthread iterator J2EE j2ee api j2ee design pattern j2ee design pattern interview questions j2ee design patterns j2ee hibernate interview questions j2ee history j2ee interview j2ee interview questions j2ee mvc j2ee mvc pattern j2ee programmer j2ee questions j2ee servlet api j2ee session j2ee struts interview questions java java 5 tutorial Java 8 java arrays java assertions java assignments java awt questions java bean java bean scope java beans java beginners tutorial Java career java certification Java Class java collection interview questions and answers java collection tutorial java collections java collections interview questions java constructors java currency Java CV java data base connectivity java database connectivity java database connectivity interview questions and answers java dates java design pattern java design patterns java developer certification Java EE java encapsulation java enums java event listeners java exceptions java formatting java garbage collection java garbage collector java gc java heap Java I/O java inheritance java input output Java Interface Java Interview Java Interview Answers Java Interview Questions Java Introduction java io java IO tutorial java iterator java jdbc Java JSON tutorial Java Key Areas java lists java literals java locks nested Java Media Framework java methods java multithreading Java multithreading Tutorials java nested locks java networking tutorial java numbers Java Objects java operators java overloading java parsing Java Programming Tutorials java race conditions java regex java regular expressions Java resume java scjp java searching java serialization java server pages java server pages api java server pages questions java spring interview questions. j2ee spring interview questions java stack java strings java swing java swing event listeners java swing frame java swing images java swings java swings images java thread explicit locking java thread lock scope java thread locking java thread locking mechanism java thread locking objects java threads java threads race condition java tips java tokenizing Java Tools Java Tutorial java ui questions Java Utilities java variables java wrappers Java xml tutorial java.lang java8 javabean javabean accessing javabean scope JavaBeans javac JavaEE JavaFX JavaFX 3D JavaFX 8 JavaOne JavaScript JavaTips JDBC jdbc driver jdbc example jdbc interview questions jdbc interview questions and answers jdbc interview questions with answers jdbc sample code JDBC Tutorial jdbc type 1 driver jdbc type 2 driver jdbc type 3 driver jdbc type 4 driver Jdeveloper JDK JDK8 JEE Tutorial jframe jframe creation jframe position jframe positioning JIRA JMeter JMS JMX join() joining threads JPA JQuery JS JSF JSF Tutorial JSONP JSP jsp and java beans jsp and servlets jsp and xml jsp api jsp code jsp compilation jsp conversion jsp directives jsp error page jsp error page directive jsp implicit objects jsp interview jsp interview questions jsp introduction jsp intvw questions jsp life jsp life cycle jsp life-cycle jsp lifecycle jsp page directive jsp questions jsp sample jsp scripting jsp scriptlets jsp servlets jsp summary jsp synopsis jsp tag libraries jsp tag library jsp taglib jsp tags jsp technology jsp to servlet jsp to servlet conversion jsp translation jsp usage jsp usebean jsp xml tags jsp xml tags usage jsp-servlet jsp:getProperty jsp:setProperty jsp:usebean jsps JSTL JUnit testing keyword synchronized keyword volatile Keywords Lambda Expressions Learning libraries life cycle life cycle of a jsp life cycle of a servlet life cycle of a thread life cycle of jsp life cycle of threads lifecycle of a thread linked list linkedhashmap linkedhashset linkedlist linux List listeners lists Literals locale lock manager pattern lock scope locking objects using threads log Logging logging errors logical and logical operators logical or loops loosely coupled making an arraylist making threads sleep making threads sleep for time MapReduce maps maps usage Maven Maven Tutorial max priority member access method arguments method local inner class method overloading method overriding method return types methods creating classes min priority Miscellaneous mobile mock exam model view controller model view controller design pattern model view controller pattern Multi Threading Multi-threading multiple threads multiplication multithreading multithreading in java multithreading interview questions multithreading questions mvc mvc design pattern mvc pattern MyEclipse mysql nested java lock nested java locks nested java thread locks nested locks nested thread locks NetBeans Networking new news nio NonAccess Modifiers norm priority normal inner class Normalization not equal to Notepad notify notifyall number format numberformat numbers object comparison object notify object orientation object oriented object oriented programming Object Oriented Programming in java objects interview questions ocmjd certification ocmjd certification eligibility OO OO Java oops OpenCSV OpenCV opening jsp tags OpenJDK OpenJFX Operators or Oracle Oracle ADF Mobile Oracle Certified Exams oracle certified master java developer oracle database ORM other topics out overloading overloading constructors overloading in java overriding page page directive page scope parsing passing variables passing variables to methods performance Platform Playing with Numbers points to remember polymorphism positioning a frame post practice exam Primitive Casting primitive variables printwriter priority queue priority queues priorityqueue priorityqueues private processing form values Products programming Projects protected public put questions questions on garbage collection questions on java strings queue quick recap quick review race conditions read objects from stream reading http request header RealTime_Tips redirecting to another servlet redirection reference reference variable casting reference variables Refreshing Java regex Regular Expressions regular inner class relational operators reminder request request dispatcher request forwarding request header request object. httpservletrequest request scope requestdispatcher response RESTClient RESTful retrieving values from session return error codes return types returning values runnable runnable interface running running java programs RUP sample jsp sample questions sample questions scwcd sample servlet scanner Scene Builder scjd certification scjd certification eligibility requirements scjp SCJP Certification scjp exam scjp exam questions scjp exam sample questions scjp questions scjp test scjp test questions scope scope of java locks scope of java thread locks scope of locks scripting in jsp scriptlet tags scriptlets scriptlets in jsp pages scwcd scwcd certification scwcd certification practice exam scwcd exam scwcd exam questions scwcd jsp summary scwcd mock exam scwcd mock exam answers scwcd practice exam scwcd practice test scwcd questions scwcd test SDLC searching searching arrays searching collections searching in java searching treemap searching treesets security self assement self assement scwcd self assessment scjp self test self test scjp self test scwcd send error method senderror method sending error code to browser serialization serialization in java serialization interview questions Serialization on Swing serialization questions service service method servlet servlet and forms servlet and jsp servlet api servlet attributes servlet code servlet container servlet context servlet error handling servlet exception handling servlet handling http request servlet initialization servlet initialization parameters servlet interview servlet interview questions servlet interview questions with answers servlet intvw questions servlet life cycle servlet lifecycle servlet questions servlet questions with answers servlet request servlet request dispatcher servlet request type servlet skeleton servletcontext servletcontextevent servletrequest Servlets servlets and jsps servlets api servlets details servlets request handling session session clean up session event listeners session facade pattern session interview questions session invalidation session listeners session management session questions session scope session timeout session tracking through url rewriting set collections set status method setattribute sets setstatus method setting bean property setting request type short circuit operators Singleton sleep sleeping threads soapUI Software Installation sorting sorting arraylist sorting arrays sorting collections special collections special inner classes split spring spring and hibernate interview questions spring batch Spring Core Spring Framework Spring Integration spring interview questions Spring JDBC Spring MVC Spring security Spring tutorial SQL SQL and database tutorial examples SQL Tutorial SSL stack stacks stacks and heaps static static class static declaration static imports static inner static inner class static method Static variable stopped stopping a thread stopping thread stopping threads Stored Procedure storing values in session Streams strictfp StrictMath string string buffer string builder string class string formatting String Handling string interview questions string manupulation string questions string tokenizer stringbuffer stringbuffer questions stringbuilder Strings strings in java struts Struts 1 Struts 1.2 Struts 2 struts framework interview questions struts interview questions struts interview questions with answers struts mvc interview questions struts questions Struts2 StrutsBooks submitting request subtraction Sun Certification sun certified java developer Sun Certified Java Programmer swing swing action performed swing and colors Swing Components swing event handling swing event listeners swing events Swing Hacks swing images Swing Look And Feels swings swings frame switch block switch case block switch case statement Sybase Sybase and SQL Server synchronization synchronized code synchronized keyword synchronized method System Properties tag lib tag library tag-lib taglibs tags TDD Technical Blogging ternary operator Test Driven Development test scjp Testing the context the session the volatile keyword thread thread class thread deadlocks thread interaction thread interruption thread life cycle thread lifecycle thread lock scope thread locks thread notify thread priorities thread race conditions race conditions in threads thread sleep thread states thread stoppage thread stopping thread synchronization thread syncing thread yield Threads threads in java threads interview questions threads life cycle threads questions tibco tightly coupled tips tips and tricks tips.FXML tokenizing Tomcat Tools toString transitions treemap treeset tricks Tricks Bag try catch try catch finally. finally block Tutorial type casting in java ui programming with java swings UML unboxing unit testing unix url rewriting use bean usebean using a arraylist using collections using colors using colours using command line arguments using different fonts using expressions using font using fonts using fonts in swings using hashmap using http session using httpsession using iterator using java beans in jsp using javabean in jsp using javabeans in jsp using javac using lists using maps using request dispatcher using scriptlets using session persistense using sets using special fonts using system properties using the jsp use bean using treeset using use bean Using Variables using volatile Using Wrappers using xml in jsp Util pack value object value object design pattern value object pattern var-args varargs Variable Arguments Variables vector vector questions vectors visibility vo pattern volatile volatile keyword volatile variables wait method waiting web app exception handling web app interview web application deployment web application exceptions web application scope web application security web component developer web component developer certification web context web context interfaces web context listeners web interview questions web security web server web servers Web services web.xml web.xml deployment webapp log weblogic website hacking website security what are threads what is a java thread what is a thread what is thread while loop windows windows 8 wrapper classes wrappers write objects to stream WSAD xml xml and jsp xml tags xslt yield()