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| Ans. OAuth is an open-standard authorization protocol or framework that describes how unrelated servers and services can safely allow authenticated access to their assets without actually sharing the initial, related, single logon credential. Like using Google or Facebook to login to something. | ||||
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 Discuss Correct / Improve   Asked in 17 Companies | ||||
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| Ans. Both Arrays and ArrayLists are used to store elements. Elements can be either primitives or objects in case of Arrays, but only objects can be stored in Arraylist. Array is a fixed length data structure while arraylist is variable length collection class. Once created, you cannot change the size of the arrays, but arraylists can dynamically resize itself when needed.Another notable difference between Arrays and Arrayslist is that arary is part of core java programming and array list is part of collection classes | ||||
 Sample Code for arrays
arraylist | ||||
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Discuss Correct / Improve array arraylist array vs arraylist Asked in 7 Companies  basic  frequent | ||||
 Frequently asked. | ||||
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| Ans. Iterator is an interface that provides methods to iterate over any Collection. | ||||
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| Discuss Correct / Improve java collections iterator Asked in 11 Companies basic frequent | ||||
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| Ans. Transient variables are variable that cannot be serialized. | ||||
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| Discuss Correct / Improve java serialization transient Asked in 15 Companies intermediate rare | ||||
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| Ans. S3 and S4 are pointing to different memory location and hence Output 1 will be false. Hash code is generated to be used as hash key in some of the collections in Java and is calculated using string characters and its length. As they both are same string literals, and hence their hashcode is same.Output 2 will be true. | ||||
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| Discuss Correct / Improve java string hashcode hash code string comparison string pool | ||||
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| Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc. | ||||
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| Discuss Correct / Improve java string hashcode hash code string comparison hashtable Asked in 17 Companies basic frequent | ||||
| Very Frequently asked. Favorite question in walkins and telephonic interviews. Usually among first few questions. Asked in different variants. Must know for intermediate and expert professionals.Among Top 10 frequently asked questions. | ||||
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| Ans. A Class must override the hashCode method if its overriding the equals method. | ||||
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| Discuss Correct / Improve java collections hashcode hash code equals collections Asked in 44 Companies intermediate frequent | ||||
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| Very frequently asked. Usually followed by questions related to private constructor and synchronized access. Frequently asked in JPMorgan and TCS (Based on 2 feedback) | ||||
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| Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html | ||||
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| Discuss Correct / Improve java design pattern singleton at&t ebay fidelity india united healthcare india Asked in 46 Companies intermediate frequent | ||||
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| Ans. Criteria is a simplified API for retrieving entities by composing Criterion objects. For example - session.createCriteria(Employee.class).add( Restrictions.like("name", "A%") ).list(); will return all employee objects having name starting with A. | ||||
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| Discuss Correct / Improve hibernate hibernate criteria Asked in 7 Companies Basic Frequent | ||||
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| Ans. We are using Agile methodology. I attend daily stand up where the development leads takes the status of assigned stories, achievements, any bottlenecks or challenges. We follow iteration of 2 weeks. | ||||
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| Discuss Correct / Improve sdlc agile methodology software system analyst software developer interview development lead project lead interview Asked in 14 Companies frequent | ||||
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| Ans. I am working as a Software System Analyst that specializes in understanding Business Requirements, Analyzing them , Performs Cost / Benefit analysis, Make suggestions to business , translate the business requirements into technical requirements, Discuss their feasibility with the technical team, performs sizing in coordination with developers and prepare high level design document. | ||||
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| Discuss Correct / Improve system analyst software system analyst software business analyst Asked in 4 Companies frequent | ||||
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| Ans. Collision is the situation when two different elements have the same Hash Code. | ||||
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| Discuss Correct / Improve java collections collision hashcode hash code hash collections ebay Asked in 1 Companies intermediate frequent | ||||
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| Ans. We are using cluster of Web servers and Application servers. Load Balancer is used to manage the load between them. Down the layer we have middleware server and then DB server to access database. | ||||
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| Discuss Correct / Improve architecture production support java servers application support Asked in 7 Companies frequent | ||||
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| Ans. Fail Safe systems are tolerant systems that continue processing even if they sense any problem. the objective here is to continue with the processing even if there are some problems instead of completely shutting it down. Example could be to catch an exception and still letting it complete with partial results. | ||||
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| Discuss Correct / Improve fail safe systems system design exception handling Asked in 3 Companies | ||||
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| Ans. [Open Ended Answer] | ||||
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| Discuss Correct / Improve elsevier open ended questions overstock.com cerner Asked in 15 Companies frequent | ||||
| Must know at all levels. Among Top 10 frequently asked questions in Java. Very frequently asked to fresh graduates or less experienced professionals. | ||||
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| Ans. Its a facility for code reuse and independent extension wherein a derived class inherits the properties of parent class. | ||||
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| Discuss Correct / Improve inheritance object oriented programming (oops) oops concepts oops concepts java concepts code reuse code re-use classes derived classes Asked in 14 Companies basic frequent | ||||
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| Ans. Destructor is used to de-allocate memory allocated by objects. There are no destructors in Java. Alternatively, Java provides Automatic garbage collection i.e automatically releasing the un-referenced memory. | ||||
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| Discuss Correct / Improve destructor garbage collection Asked in 11 Companies Basic frequent | ||||
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| Ans. <a href="http://www.programcreek.com/2009/02/diagram-for-hierarchy-of-exception-classes/" rel="nofollow">http://www.programcreek.com/2009/02/diagram-for-hierarchy-of-exception-classes/</a> | ||||
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| Discuss Correct / Improve exception hierarchy exceptions Asked in 3 Companies | ||||
| Frequently asked question in companies using Rest Web services. | ||||
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| Ans. PUT requests are only meant to place the object as it is on server. For example - You want a file to be uploaded and then placed in a particular folder or you want an Employee object to be persisted in the table. POST requests are also meant to transfer information from client to server but that information once received at the server is evaluated , modified or refactored before persisting. | ||||
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| Discuss Correct / Improve Put vs Post Rest Asked in 5 Companies frequent | ||||
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| Ans. Enums in Java are used to declare predefined objects and then reuse them. they offer many benefits 1. Enum instance are type safe and thread safe. 2. Enum instances are singleton and hence reused. 3. If we use Enums with Switch , It makes sure that the passed argument is either of its instance and hence provides a safeguard. 4. If we use Enum with Sorted Collections we can sort the elements with a predefined priorities ( as per constant declaration in enum ) 5. We can use Enum as a Factory by defining its constructor. 6. We can store related constant data within enum. For example - If we know the values for the map upfront, we can alternatively use an enum. | ||||
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| Discuss Correct / Improve Asked in 6 Companies | ||||
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| Ans. We can use external table feature of Oracle. | ||||
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| Discuss Correct / Improve Asked in 1 Companies Intermediate | ||||
| Frequently asked Design Pattern interview question. | ||||
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| Ans. The prototype pattern is a creational design pattern. It is used when the type of objects to create is determined by a prototypical instance, which is cloned to produce new objects. Prototype is used when we need duplicate copies of objects. | ||||
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| Discuss Correct / Improve design pattern prototype design pattern cloning Asked in 11 Companies intermediate | ||||
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| Ans. <a href="http://javahungry.blogspot.com/2015/03/difference-between-array-and-arraylist-in-java-example.html" rel="nofollow">http://javahungry.blogspot.com/2015/03/difference-between-array-and-arraylist-in-java-example.html</a> | ||||
| Sample Code for ArrayList | ||||
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| Discuss Correct / Improve array arraylist Asked in 11 Companies basic frequent | ||||
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| Ans. 59 23 28-31 * * [ "$(date +%d -d tomorrow)" = "01" ] && job_name | ||||
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| Discuss Correct / Improve unix crontab Asked in 1 Companies | ||||
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| Ans. du -a /var | sort -n -r | head -n 10 | ||||
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| Discuss Correct / Improve unix command Asked in 1 Companies | ||||
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| Ans. PID - process identification number is an identification number that is automatically assigned to each process when it is created USER - User Name PR - PR is the process actual priority NI is the nice value, which is a user-space concept. VIRT -Virtual Image (kb). The total amount of virtual memory used by the task. RES - Resident size (kb). The non-swapped physical memory a task has used. SHR - Shared Mem size (kb). The amount of shared memory used by a task. S - Process Status. The status of the task which can be one of: D = uninterruptible sleep R = running S = sleeping T = traced or stopped Z = zombie %CPU - % CPU usage %MEM - % MEM Usage TIME - Total CPU time the task has used since it started. COMMAND - Command which was used to execute the process | ||||
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| Discuss Correct / Improve top command unix command Asked in 1 Companies | ||||
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| Ans. An Exception in java is the occurrence during computation that is anomalous and is not expected. Exception handling is the mechanism which is used to handle such situations. | ||||
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| Discuss Correct / Improve exception handling Asked in 18 Companies basic frequent | ||||
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| Ans. General contract of hashCode is: 1.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, 2.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. 3.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. | ||||
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| Discuss Correct / Improve hashcode Asked in 1 Companies expert | ||||
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| Ans. [Open Ended Answer] The objective of the question is to check how efficient one is in the language so that appropriate level questions are asked. Don't tell too high number if you are being interviewed for a junior or mid level position as the interviewer may throw advance level questions. | ||||
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| Discuss Correct / Improve Asked in 17 Companies | ||||
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| Ans. PATH, CLASSPATH and JAVA_HOME | ||||
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| Discuss Correct / Improve environment variables path classpath java_home Asked in 3 Companies basic frequent | ||||
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When String literals are compared using ==, they always returns true if the string values are same because .. 
