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Interview Questions and Answers - Order By Rating | ||||
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Ans. No exit is a method to exit execution of a program. | ||||
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Like Discuss Correct / Improve  exit  keywords  exit a program Asked in 1 Companies | ||||
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Ans. No, delete is not a keyword in Java. Destruction of objects is taken care by Java Garbage Collection mechanism. | ||||
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Ans. It uses those low order bytes of the result that can fit into the size of the type allowed by the operation. | ||||
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Like Discuss Correct / Improve  integer  data types Asked in 1 Companies   rare | ||||
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Ans. 1. Wrap the desired code in try block followed by a catch / finally to catch the exception 2. Declare the throws clause with exceptions that the code is expected to throw as an indication to the calling method to take care of it. | ||||
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Ans. No, Java doesn't have a sizeOf operator. In C / C++ , its required to determine how much memory allocation is required which is not the case with Java. Java handles memory allocation and deallocation intrinsically. | ||||
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Like Discuss Correct / Improve  sizeOf  size of object  sizeOf operator Asked in 1 Companies   rare | ||||
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Ans. It's weird that compiler doesn't complain if we declare transient with static variable because it makes no sense. At least a warning message saying "transient is useless in this situation" would have helped with code cleaning. Static variables are never serialized and transient is an indication that the specified variable shouldn't be serialized so its kind of double enforcement not to serialize. It could be that as it makes no different to the variable behavior and hence using both keywords with a variable are permitted. | ||||
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Like Discuss Correct / Improve  static  transient  serialization Asked in 1 Companies expert   rare | ||||
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Ans. 1. Objects are serialized and not classes and hence Static variables are ignored. 2. Transient is an explicit declaration to ignore the variable during serialization and hence transient instance variables are ignored too. 3. Base class instance variables if the base class hasn't been declared serializable. | ||||
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Ans. Null | ||||
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Like Discuss Correct / Improve  object reference  null Asked in 1 Companies basic | ||||
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Ans. No, we should be lean in loading only packages which are required. Loading packages which are not being used result in memory overheads. | ||||
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Ans. No, but we can use wild card (*) to do so For example - import java.util.* will import all packages with name starting with java.util | ||||
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Ans. We can overload the main method by specifying different argument types. For example - 2 main methods with different arguments is perfectly legal public static void main(); public static void main(String[] args); The following are not legal as compiler will complain of duplicate methods public static void main(String[] args); public static void main(String[] args); Even The following are not legal as we cannot overload on return types public static String main(String[] args); public static void main(String[] args); | ||||
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Like Discuss Correct / Improve  main method Asked in 2 Companies | ||||
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Ans. Yes we can have a main method with string[] argument in every class of an application. When we execute an app we specify the starting point i.e the class that will get the control first and hence main method of that class gets executed. | ||||
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Ans. PATH, CLASSPATH and JAVA_HOME | ||||
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Like Discuss Correct / Improve  environment variables  path  classpath  java_home Asked in 3 Companies basic   frequent | ||||
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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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Frequently asked in Cognizant ( Based on 2 feedback ) | ||||
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Ans. Inner join is the intersection of two tables on the condition defined by the where clause i.e will get records from both tables matched by a column. Outer join is the union of two tables i.e will get all records from both tables and will put null in the columns where related records are not present. Left Outer join is the left union of two tables i.e all records from the table on the left and values from the right table for related records else null for the columns from right table. Right Outer join is the right union of two tables i.e all records from the table on the right and values from the left table for related records else null for the columns from left table. | ||||
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Like Discuss Correct / Improve  sql  inner join  outer join  right join  left join Asked in 24 Companies basic   frequent | ||||
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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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Ans. https://en.wikipedia.org/wiki/Database_normalization | ||||
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Like Discuss Correct / Improve  normalization  database Asked in 35 Companies intermediate   frequent | ||||
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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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Ans. du -a /var | sort -n -r | head -n 10 | ||||
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Ans. 59 23 28-31 * * [ "$(date +%d -d tomorrow)" = "01" ] && job_name | ||||
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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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Like Discuss Correct / Improve  array  arraylist Asked in 11 Companies basic   frequent | ||||
Very Frequently asked to Senior Software Engineers or Developers. | ||||
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Ans. [Open Ended Answer] | ||||
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Like Discuss Correct / Improve  design patterns Asked in 17 Companies intermediate   frequent | ||||
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Ans. 1. HashSet doesnt maintain its elements in any specific order and is all random whereas TreeSet maintains elements in natural order 9 order defined by the equals method of TreeSet element type ) 2. TreeSet doesnt allow null elements whereas HashMap does. 3. As TreeSet orders elements and is hence insertion is comparatively slower. 4. HashSet performs basic operations like add(), remove(), contains(), size() etc. in a constant size time. A TreeSet performs these operations at the order of log(n) time. 5. HashMap in Java internally backs a HashSet. A NavigableMap backs a TreeSet internally. | ||||
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Ans. Coupling is the degree of interdependence between software modules, a measure of how closely connected two modules are or the strength of the relationships between modules. Cohesion refers to the degree to which the elements of a module belong together. Cohesion measures the strength of relationship between pieces of functionality within a given module. | ||||
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Basic and Very Frequently asked. | ||||
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Ans. Polymorphism means the condition of occurring in several different forms. Polymorphism in Java is achieved in two manners 1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas 2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding. | ||||
Sample Code for overloading Sample Code for overriding | ||||
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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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Like Discuss Correct / Improve  design pattern  prototype design pattern  cloning Asked in 11 Companies intermediate | ||||
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Ans. We can use external table feature of Oracle. | ||||
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Like Discuss Correct / Improve   Asked in 1 Companies Intermediate | ||||
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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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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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Ans. GET is supposed to get information from the server. Client sends the minimal information so that Server can respond with the response body on basis of request. For example - You want to get complete employment record for employee id 123 POST is supposed to send the information for submission. Payload or a Body is usually sent so that it can be persisted on the server. For example - Sending the complete information of an employee ( id, name , dept etc ) to the server for persisting it. | ||||
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Like Discuss Correct / Improve  get vs post   web service   rest Asked in 11 Companies basic   frequent | ||||