InstanceOfJava

Java objective type questions and answers on static keyword

Posted by: Instanceofjava Posted date: December 20, 2016 / comment : 0 core java multiple choice questions with answers

1.Static means

Class level

Object level

2.Main method is static because to execute main method without creating object By JVM

Yes

3.We can overload static methods

True

False

4.We can override static methods

Yes

5.Can we write static public void main(String [] args)?

Yes

6.What is the output of below program ?

java multiple choice questions with answers

x=10 x=10

x=10 x=20

x=30 x=30

x=30 x=20

Java mcq with answers on this keyword

Posted by: Instanceofjava Posted date: December 19, 2016 / comment : 0 core java multiple choice questions with answers

1.this always will points to

Current class object

Super class object

2.We can use this in static methods?

True

False

3.Can we call static methods using this from non static methods

Yes

4.We can return this from a method as return type

True

False

5.What is the output of below program

Hello instanceofjava

compile time error

Run time exception

Core java multiple choice questions with answers on method overloading

Posted by: Instanceofjava Posted date: December 19, 2016 / comment : 0 core java multiple choice questions with answers

1.Method overloading means?

Multiple methods with same name same arguments

Multiple methods with same name different arguments

Multiple methods with different name different arguments

2.Method overloading also known as?

Dynamic polymorphism

Static polymorphism

3.Can we overload main method?

Yes

4.Which is incorrect statement regarding overloading?
(which is incorrect about method overloading)

Method with same name and differ in number of arguments

Methods should be with same name and different return type

Methods should be same name and differ in order of type of arguments

Methods should be with same name and differ in type of arguments

5.What is the output of below program?

hello

compile time error

Run time exception

Java mutliple choice questions with answers on constructors

Posted by: Instanceofjava Posted date: December 18, 2016 / comment : 2 core java multiple choice questions with answers

On the request of many friends we added java multiple questions with answers.
Java mcq questions with answers on constructors.
We will add all java topics multiple questions with answers for freshers and experienced.

1.Can we define method with same name of class?

Yes

2.What happens if we add return type to constructor?

Compile time error

Run time Error

JVM treats that as method

3.We can declare constructor as private?

True

False

4.What is default accessibility modifier of a default constructor

public

private

Same as class accessibility modifier

default

5.What is the output of following program

How are you Hello Hi

Hi Hello How are you

How are you Hi Hello

How to get java source files from jar file

Posted by: Instanceofjava Posted date: November 27, 2016 / comment : 1 Core java Interview Questions

Jar : Java Archive is a group of .class files.
We can create a jar file using following commands
jar -cvf example.jar test.class
jar -cvf example.jar *.*
To unzip from jar file we need to use following command.
jar -xvf instanceofjava.jar

How to get source code from jar file using java De-compilers

We can get source code from java file by using java De-compilers.
You can download http://techieme.in/resources-needed/ JDGUI from internet.

how to get source code from jar file in eclipse

Open JD-GUI and File -> open -> open target jar file.
It will show java source code.

How to extract java files from jar in eclipse

We can get java source files from jar file by using eclipse also for this we need to add a plugin.
Download jar file from http://jd.benow.ca/
Unzip it . you will get jd.ide.eclipse.plugin_1.0.0.jar file and add it to eclipse plugin folder.
And restart your eclipse.
Add target jar file to a project and now click on the file you will get source code.
You can add target jar file using java project->java buildpath -> add external jars option

how to convert jar to java source in eclipse

Here i added jstl core jar to eclipse to see java source files.
Click on the file now it will show source code
How to extract java files from jar

how to extract java files from jar in eclipse

Hibernate Native sql query with example

Posted by: Instanceofjava Posted date: November 07, 2016 / comment : 0 hibernate interview questions , Hibernate Tutorial

By Using Hibernate Native SQL we can write database dependent queries as part of hibernate.
Hibernate Native Sql allows us to write create , update, delete and insert queries.
We can also call Stored procedures using Hibernate Native Sql.
When the query is too complex using HQL then we need to use hibernate sql query.
Hibernate uses the org.hibernate.SQLQuery interface for native SQL
1. SQLQuery is a sub interface of Query
2. Use createSQLQuery() factory method on Session to create SQLQuery object.

Hibernate SQLQuery must be associated with an existing Hibernate entity or scalar result.

Hibernate native sql insert query example

Session session = sessionFactory.openSession();
session.beginTransaction();
SQLQuery insertsqlQuery = session.createSQLQuery("INSERT INTO
Physician(firstname,lastname,fee,hospital)VALUES(?,?,?,?)");
insertsqlQuery.setParameter(0, "Saidesh");
insertsqlQuery.setParameter(1, "Kilaru");
insertsqlQuery.setParameter(2, 50);
insertsqlQuery.setParameter(3, "Yashoda");
insertsqlQuery.executeUpdate();

Hibernate scalar query example

Writing a Hibernate Sql query to get list of scalars or values from single or multiple tables.
Lets see an example on Hibernate scalar query.

String hibernate_sql = "SELECT first_name, fee FROM Physician";
SQLQuery query = session.createSQLQuery(hibernate_sql);
query.setResultTransformer(Criteria.ALIAS_TO_ENTITY_MAP);
List results = query.list();

Hibernate named sql Queries

Writing a Hibernate Sql query to get entity object by using addEntity() method.
Lets see an example on Hibernate named sql query

hibernate native sql query parameters scalar

Hibernate Named Query Introduction Tutorial

Posted by: Instanceofjava Posted date: November 06, 2016 / comment : 0 hibernate interview questions , Hibernate named query , Hibernate Tutorial

If we are using HQL or Native SQL queries multiple time then it will be code mess because all queries will be scattered throughout the project.
Hibernate Named Query is a way to use queries by giving a name.
Hibernate Named Queries will be defined at one place and used anywhere in the project.
use of named query in hibernate
Writing HQL query in HBM file is called HQL Named Query.
Or we can use @NameQuery annotation in entity.
For writing Hibernate Named Queries we will use <query> tag in Hibernate mapping file Or @NameQuery annotation in the entity.
If we want to create Named Query using hibernate mapping file then we need to use query element.

Advantages of Named Query in Hibernate

Global access
Easy to maintain.

Hibernate Named Queries by using Annotations:

If we want to create Named Queries using annotations in entity class then we need to use @NameQueries and @NameQuery annotations
@NameQuery will be used to create single Query
@NameQueries annotations will be used to create multiple Queries. When we are using @NameQueries for every query we need to use @NameQuery annotation.

Hibernate Named Query example by using Annotations:

Query query = session.getNamedQuery("findDocterById");
query.setInteger("id", 37);
List empList = query.list();

Hibernate Named Queries by using Hibernate mapping file:

We need to configure Hibernate Named Queries as part of Hibernate mapping file.
By using <query> element we need to write Hibernate named Queries.

<hibernate_mapping>
<class >
---------
</class>
<query name = “findDocterById”>
<![CDATA[from Docter s where s.id = :id]]>
</query>
</hibernate_mapping>

Query query = session.getNamedQuery("findDocterById");
query.setInteger("id", 64);
List empList = query.list();

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