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Q361. What entries we make in the hibernate config file if we are not using hbm files but Annotations ?

Hibernate

Ans. We configure Entity classes having annotated mappings.

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Q362. How many SessionFactory and Session objects are created ?

Java EE

Ans. Single SessionFactory object and multiple session objects for opening different session. Hibernate creates new Session object per thread.

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Q363. What is the use of hbm2ddl Configuration in Hibernate ?

Hibernate

Ans. This configuration specifies if hibernate should creates the Schema / Table on its own if the respective table is not found.

"update" doesn't create the table if it's not found whereas configuration set as "create" creates the schema automatically.

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Q364. What is the difference between these 2 annotations ?

@Entity

@Entity ( name="EMPLOYEES" )

Hibernate

Ans. The first annotation will try to map the Class with the Table as of same name as Class whereas the second annotation will specify the Entity name as "EMPLOYEES" and hence will try to map with Table Name "EMPLOYEES".

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Q365. What is the difference between these 2 annotations ?

@Entity ( name ="EMPLOYEES")
@Entity @Table ( name=""EMPLOYEES"" )

@Entity ( name="EMP")
@Table ( name="EMPLPYEES" )

Hibernate

Ans. First Annotation will set the Entity name as EMPLOYEES and hence will try to map with the same Table name.

The second annotation will make the Entity mapped to table EMPLOYEES irrespective of the Entity Name ( which is class name in this case ).

Third Annotations will set the different names for Enitity and Table and will explicitly map them.

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Q366. What are the different ID generating strategies using @GeneratedValue annotation ?

Hibernate

Ans. Auto , Identity , Sequence and Table.

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Q367. How to do Eager loading in Hibernate ?

Hibernate

Ans. Using

lazy = false in hibernate config file

or

@Basic(fetch=FetchType.EAGER) at the mapping

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Q368. What is cascade ?

Hibernate

Ans. Instead of Saving Parent as well as Child Entities individually , Hibernate provides the option to persist / delete the related entities when the Parent is persisted.

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Q369. Which type of associated Entities are Eagerly loaded by Default ?

Hibernate

Ans. OneToOne

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Q370. After which Hibernate version , related Entities are initialized lazily ?

Hibernate

Ans. After Hibernate 3.0

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Q371. What is the difference between int[] x; and int x[]; ?

Core Java

Ans. No Difference. Both are the acceptable ways to declare an array.

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Q372. What are the annotations used in Junit with Junit4 ?

Ans. @Test

The Test annotation indicates that the public void method to which it is attached can be run as a test case.

@Before

The Before annotation indicates that this method must be executed before each test in the class, so as to execute some preconditions necessary for the test.

@BeforeClass

The BeforeClass annotation indicates that the static method to which is attached must be executed once and before all tests in the class.

@After

The After annotation indicates that this method gets executed after execution of each test.

@AfterClass

The AfterClass annotation can be used when a method needs to be executed after executing all the tests in a JUnit Test Case class so as to clean-up the set-up.

@Ignores

The Ignore annotation can be used when you want temporarily disable the execution of a specific test.

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Q373. What is asynchronous I/O ?

Ans. It is a form of Input Output processing that permits other processing to continue before the I/O transmission has finished.

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Frequently asked these days as there are major changes in Java 8.

Q374. What are new features introduced with Java 8 ?

Core Java

Ans. Lambda Expressions , Interface Default and Static Methods , Method Reference , Parameters Name , Optional , Streams, Concurrency.

Sample Code for Lambda

Sample Code for interface default

Sample Code for Optional

Sample Code for Streams

Sample Code for java.time

Sample Code for Predicate

Sample Code for Consumer

Sample Code for MapMerge

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Q375. What does the following lambda expression means ?

helloJava8 ( x-> x%2 )

Ans. helloJava8 receives an Integer as argument and then returns the modulus of that Integer.

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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)

Q376. Explain Singleton Design Pattern ?

Design

Ans. http://www.buggybread.com/2014/03/java-design-pattern-singleton-interview.html

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Q377. How can we protect an application from throwing a NullPointerException ?

Ans. By having Null Checks.

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Q378. What are the conventions regarding constant variables or static final variables ?

Core Java

Ans. They should be named all in upper case with underscore separating words.

Moreover the name should be such that it identifies the value. For example, if we are using constant for employee Id 123, it should be named something like EMPLOYEE_ID_123 and not EMPLOYEE_ID

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Q379. What will the following code do ?

String dateStr = "2011 11 19";
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
Date date = dateFormat.parse(dateStr);
System.out.println(date);

Ans. It will throw the ParseException as the date format doesn't abide with the format of the specified date.

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Q380. What will be the output of this code ?

Set mySet = new TreeSet();
mySet.add("4567");
mySet.add("5678");
mySet.add("6789");
for(String s: mySet){
System.out.println(s);
}

Ans. 4567
5678
6789

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Q381. public enum Day {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
THURSDAY, FRIDAY, SATURDAY
}

public class Test {
Set mySet = new HashSet();
mySet.add(Day.MONDAY);
mySet.add(Day.SUNDAY);
mySet.add(Day.SATURDAY);

for(Day d: mySet){
System.out.println(d);
}
}

Ans. SUNDAY
MONDAY
SATURDAY

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Try 3 Question(s) Test

Q382. Tell me something about AssertionError ?

Core Java

Ans. AssertionError is actually a fatal fault or a bug in the program. We may not like to continue program , request or thread execution if this error occurs as this condition is the assumption to continue further execution.

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Q383. Shall we keep the enumeration name in all capital letters as it contains all constants ?

Ans. Enum is actually a class with pre defined constants. So enum name should follow the convention of the Class name. Though the constant names or the Enum variables should follow the convention of having all capital letters.

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Q384. How is HashSet maintained in memory by Java ?

Core Java

Ans. HashSet is maintained as HashMap by Java with values of the HashSet as Keys of the HashMap and value of the HashMap as the constant PRESENT.

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Not frequently asked as it was introduced with Java 8.

Q385. What is the @FunctionalInterface annotation ?

Core Java

Ans. This is an informative annotation that specify that the interface is a functional interface. A Function Interface has only one abstract method and many default methods. Compiler generates an error if the interface specified with the annotation doesn't abide by the specifications for functional interface.

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Q386. Which version control (VC) or software configuration management (SCM) systems work with Merge?

Scm

Ans. You can use Tortoise SVN,which has Merge Utility embedded in it.

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Q387. Which constraint cannot be specified as an explicit constraint and should be specified with the column only ?

Database

Ans. NOT NULL

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Q388. Will this code compile ?

public class BuggyBread1{
abstract public void test();
}

Core Java

Ans. No. It will give the compilation error saying "The abstract method test in type BuggyBread1 can only be defined by an abstract class".

We need to declare the class abstract for it to have any abstract method.

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Q389. Will this Code compile ?

abstract public class BuggyBread1{
abstract public void test(){};
}

Core Java

Ans. No. This will give a compilation error saying "Abstract methods do not specify a body".

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Rarely asked as it was introduced with Java 8.

Q390. Difference between DoubleSummaryStatistics , IntSummaryStatistics and LongSummaryStatistics ?

Core Java

Ans. They all does the same task i.e to compute statistical information on the stream of data. They differ by the way they store the statistical information as they expect a different data type of the values being used.

IntSummaryStatistics and LongSummaryStatistics expect non floating point values and hence stores the statistical information like min,max and sum as non floating values ( int or long ) whereas DoubleSummaryStatistics stores these information as floating value.

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