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Q131. Write an SQL to find all records having all upper case alphanumeric characters in a field ?

Ans. Select * from Table where field = upper(field)

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Q132. Write an SQL to find all records having all numeric characters in a field ?

Ans. Select * from Table where isnumeric(field) = 1;

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Q133. 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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Q134. Do you know of any DB statement that can be used if we would like to insert multiple rows into a table ?

Database

Ans. We can use INSERT ALL.

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Q135. What is Closeable ?

Core Java

Ans. A Closeable is an interface which is a source or destination of data that can be closed.

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Q136. What is the advantage of JPA ?

Database

Ans. Its a specification that guides the implementation of ORM frameworks. Implementations abiding by the specification would mean that one can be replaced with other in an application without much hassle. Only the Features that are added over the specification needs to be taken care of if any such change is made.

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Q137. Why is a constant defined as a static final in Java?

Core Java

Ans. Final makes sure that the value doesn't change after initialization and static makes sure that there is only one copy that can be shared across objects.

Making it non static will unnecessarily create a different copy per object wherein the same value will kept for all copies ( as its final and cannot be changed ).

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Q138. What things you will look for if you get following exception while making DB call ?

table or view does not exist

Database

Ans. First will check if the table or view actually exist in the DB

If it does , Will make sure to see that the application has rights on the schema that holds the respective Table.

Will then make sure that we have prefixed the schema with the table name while accessing it.

Will then make sure that its not DB Cache that's causing it as the table DDL might have been created recently.

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Q139. What's the benefit for specifying constraints like Not Null , Primary Key explicitly instead of specifying it against the column ?

Database

Ans. In case we specify them explicitly we can have control over constraint name as otherwise they will be system generated. It provides an ease in case we plan to drop the constraint in future.

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Q140. How can we disable a constraint ?

Database

Ans. alter table
table_name
DISABLE constraint
constraint_name;

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Q141. Can we have foreign key reference to a non primary key column ?

Database

Ans. Yes, but the respective key in the foreign table should be declared Unique.

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Q142. What should be done for auto generating primary key id in a table ?

Database

Ans. We need to create a sequence.

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Q143. 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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Q144. 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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Q145. 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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Q146. How to know the structure of a Table in Oracle ?

Database

Ans. DESC

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Q147. How to know the constraints on a Table in Oracle ?

Database

Ans. SELECT *
FROM user_constraints
WHERE table_name = ''

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Q148. How to know the default column value of a Table in Oracle ?

Database

Ans. Select DATA_DEFAULT
from DBA_TAB_COLUMNS
where TABLE_NAME = '' and COLUMN_NAME='';

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Q149. How do we specify the criteria if it involves mapping between two entities or join between tables ?

Hibernate

Ans. The following code returns the list of Employee objects having employee name starting with A and Dept Name ( Department , Employee Mapped ).

session.createCriteria(Employee.class,"emp")
.createAlias("emp.department", "dept",Criteria.INNER_JOIN)
.add( Restrictions.like("name", "A%") )
.add(Restrictions.eq("dept.name","Finance")
.list();

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Q150. Name few classes that implement Cloneable interface ?

Ans. http://www.buggybread.com/2015/02/java-collections-classes-that-implement_58.html

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Q151. Name few classes that implement iterable interface ?

Ans. http://www.buggybread.com/2015/02/java-collections-classes-that-implement_45.html

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Q152. What are stateless objects ? How are they different from immutable objects ? Which of these two is thread safe ?

Object Oriented Programming

Ans. Stateless objects are the objects without instance fields (instance variables). The class may have compile time constants i.e static final fields.Immutable objects are the objects which have state but the state cannot be changed after initialization. Both are Thread safe.

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Q153. What are advantages of stateless and / or immutable objects ?

Object Oriented Programming

Ans. They can be shared across multiple threads as they are thread safe.

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Q154. If we add Enum constants to a sorted collection ( Treemap , TreeSet ), What will be the order in which they will be maintained ?

a. Sorted Collection wont maintain them in any order.
b. Insertion Order
c. Order in which constants are declared.
d. Natural Sorting Order.

Ans. Order in which constants are declared.

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Q155. Which interface does java.util.Hashtable implement ?

a. List
b. Set
c. Collection
d. Map

Core Java

Ans. Map

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Q156. Which of the following is false ?

a. HashMap came before HashTable.
b. HashMap allows null values whereas Hashtable doesnâ€™t allow null values.
c. HashTable and HashMap allow Key-Value pairs.
d. Hashtable is synchronized whereas HashMap is not.

Ans. HashMap came before HashTable.

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Q157. Which of the collections allows null as the key ?

a. HashTable
b. HashMap
c. TreeMap
d. LinkedHashMap

Core Java

Ans. HashMap

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Q158. Which of the following is not a Table tag ? a. th b. td c. tb d.

Ans. tb

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Q159. Variables of an interface are intrinsically ...

a. transient
b. final
c. public
d. static

Ans. b,c and d i.e final , public and static

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Q160. Which of the following class creates mutable objects ?

a. Boolean
b. File
c. String
d. StringBuffer

Ans. StringBuffer

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