Application Vs. Web Server

(1) Webserver serves pages for viewing in web browser, application server provides exposes businness logic for client applications through various protocols.

(2) Webserver exclusively handles http requests.application server serves bussiness logic to application programs through any number of protocols.

(3) Webserver delegation model is fairly simple,when the request comes into the webserver,it simply passes the request to the program best able to handle it(Server side program). It may not support transactions and database connection pooling.

(4) Application server is more capable of dynamic behaviour than webserver. We can also configure application server to work as a webserver.Simply applic! ation server is a superset of webserver.

(5) Web Server serves static HTML pages  or gifs, jpegs, etc., and can also run code written in CGI, JSP etc. A Web server handles the HTTP protocol. Eg of some web server are IIS or apache.

(6) An Application Server is used to run business logic or dynamically generated presentation code. It can either be .NET based or J2EE based (BEA WebLogic Server, IBM WebSphere, JBoss).

(7) A J2EE application server runs servlets and JSPs (infact a part of the app server called web container is responsible for running servlets and JSPs) that are used to create HTML pages dynamically. In addition, J2EE application server can run EJBs - which are used to execute business logic.

(8) An Application server has a 'built-in' web server, in addition to that it supports other modules or features like e-business integration, independent management and security module, portlets etc.

JAVA Vs. DOTNET

# JAVA

• Java is developed by Sun Microsystems
• Java is a light weight language and can be run on almost all the OS(it require less hardware)
• Java you need to confirm it that all the objects are destroyed before application quits.
• Java has no standard tool is available. Although, many third party IDEs are available
• Java is a programming language designed to be run on many different platforms, and so uses a common language which has to be compiled and run on different platforms (eg. windows, mac and linux).Any OS which is able to install JVMJava can be used to write programs for many different operating systems
• Java interface, a null object reference maps to the VT_NULL VARIANT value
• Java interface, all failure HRESULTs from the underlying COM interface are reported by throwing a com.ca.openroad.COMException containing that HRESULT value

# .NET

• .Net is developed by Microsoft Corporation
• .Net needs a very heavy framework to be installed which have higher Hardware requirements too compared to Java
• .Net garbage collector runs at a certain interval and see is there is any memory occupied by anyobject whose parent is now finished processing (for eg. you closed an application), in this casethe garbage collector automatically removes the reference of that object and free up the memory
• .Net a standard development IDE is available that is Microsoft Visual Studio
• .NET, takes on a different approach, by allowing you to program in any language you choose,but has compilers for many different languages that generates a platform specific code (i.e.Microsoft or Windows).
• .NET can be used to make any programming language into a Windows program.NET COM interoperability layer maps null .NET object references to VT_EMPTY. VT_NULLis mapped to a special object type of class “System.DBNull”.
• .NET COM interoperability layer does something similar, using theInteropServices.COMException class. However, it uses that exception class only as a lastresort. If there is already a .NET exception class that reasonably represents the meaning of aparticular HRESULT, the interoperability layer throws that .NET exception instead of a COMException.

Java Fundamental-V

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1. What is the use of preparedstatement?

Preparedstatements are precompiled statements. It is mainly used to speed up the process of inserting/updating/deleting especially when there is a bulk processing.


2. What is callable statement? Tell me the way to get the callable statement?

Callablestatements are used to invoke the stored procedures. You can obtain the callablestatement from Connection using the following methods prepareCall(String sql) prepareCall(String sql, int resultSetType, int resultSetConcurrency)


3. In a statement, I am executing a batch. What is the result of the execution?

It returns the int array. The array contains the affected row count in the corresponding index of the SQL.


4. Can a abstract method have the static qualifier?

No


5.. What are the different types of qualifier and what is the default qualifier?

public, protected, private, package (default)


6. What is the super class of Hashtable?

Dictionary

Java Fundamental-IV

1. What are types of J2EE clients?

Answer: J2EE clients are the software that access the services components installed on the J2EE container. Following are the J2EE clients:

a) Applets

b) Java-Web Start clients

c) Wireless clients

d) Web applications

2. What do you understand by JTA and JTS?

Answer: JTA stands for Java Transaction API and JTS stands for Java Transaction Service. JTA provides a standard interface which allows the developers to demarcate transactions in a manner that is independent of the transaction manager implementation. The J2EE SDK uses the JTA transaction manager to implement the transaction. The code developed by developers does not calls the JTS methods directly, but only invokes the JTA methods. Then JTA internally invokes the JTS routines. JTA is a high level transaction interface used by the application code to control the transaction.

Java Fundamental-III

1. When should the method invokeLater()be used?

This method is used to ensure that Swing components are updated through the event-dispatching thread.

2. How can a subclass call a method or a constructor defined in a superclass?

Use the following syntax: super.myMethod(); To call a constructor of the superclass, just write super(); in the first line of the subclass’s constructor.

3. What’s the difference between a queue and a stack?

Stacks works by last-in-first-out rule (LIFO), while queues use the FIFO rule.

4. You can create an abstract class that contains only abstract methods. On the other hand, you can create an interface that declares the same methods. So can you use abstract classes instead of interfaces?

Sometimes. But your class may be a descendent of another class and in this case the interface is your only option.

5. What comes to mind when you hear about a young generation in Java?

Garbage collection.

6. What comes to mind when someone mentions a shallow copy in Java?

Object cloning.

7. If you’re overriding the method equals() of an object, which other method you might also consider?

hashCode()

8. You are planning to do an indexed search in a list of objects. Which of the two Java collections should you use: ArrayList or LinkedList?

ArrayList

9. How would you make a copy of an entire Java object with its state?

Have this class implement Cloneable interface and call its method clone().

10. How can you minimize the need of garbage collection and make the memory use more effective?

Use object pooling and weak object references.

11. There are two classes: A and B. The class B need to inform a class A when some important event has happened. What Java technique would you use to implement it?

If these classes are threads I’d consider notify() or notifyAll(). For regular classes you can use the Observer interface.

12. What access level do you need to specify in the class declaration to ensure that only classes from the same directory can access it?

You do not need to specify any access level, and Java will use a default package access level

13. What are the contents of web module?

Answer: A web module may contain:

a) JSP files

b) Java classes

c) gif and html files and

d) web component deployment descriptor

14. Differentiate between .ear, .jar and .war files.

Answer: These files are simply zipped file using java jar tool. These files are created for different purposes. Here is the description of these files:

.jar files: These files are with the .jar extenstion. The .jar files contains the libraries, resources and accessories files like property files.

.war files: These files are with the .war extension. The war file contains the web application that can be deployed on the any servlet/jsp container. The .war file contains jsp, html, javascript and other files for necessary for the development of web applications.

.ear files: The .ear file contains the EJB modules of the application.

15. What is the difference between Session Bean and Entity Bean?

Answer:

Session Bean: Session is one of the EJBs and it represents a single client inside the Application Server. Stateless session is easy to develop and its efficient. As compare to entity beans session beans require few server resources.

A session bean is similar to an interactive session and is not shared; it can have only one client, in the same way that an interactive session can have only one user. A session bean is not persistent and it is destroyed once the session terminates.

Entity Bean: An entity bean represents persistent global data from the database. Entity beans data are stored into database.

16. Why J2EE is suitable for the development distributed multi-tiered enterprise applications?

Answer: The J2EE platform consists of multi-tiered distributed application model. J2EE applications allows the developers to design and implement the business logic into components according to business requirement. J2EE architecture allows the development of multi-tired applications and the developed applications can be installed on different machines depending on the tier in the multi-tiered J2EE environment . The J2EE application parts are:

a) Client-tier components run on the client machine.

b) Web-tier components run on the J2EE server.

c) Business-tier components run on the J2EE server and the

d) Enterprise information system (EIS)-tier software runs on the EIS servers

17. Why do understand by a container?

Answer: Normally, thin-client multi-tiered applications are hard to write because they involve many lines of intricate code to handle transaction and state management, multithreading, resource pooling, and other complex low-level details. The component-based and platform-independent J2EE architecture makes J2EE applications easy to write because business logic is organized into reusable components. In addition, the J2EE server provides underlying services in the form of a container for every component type. Because you do not have to develop these services yourself, you are free to concentrate on solving the business problem at hand (Source: http://java.sun.com/j2ee/1.3/docs/tutorial/doc/Overview4.html ).

In short containers are the interface between a component and the low-level platform specific functionality that supports the component. The application like Web, enterprise bean, or application client component must be assembled and deployed on the J2EE container before executing.

18. What are the services provided by a container?

Answer: The services provided by container are as follows:

a) Transaction management for the bean

b) Security for the bean

c) Persistence of the bean

d) Remote access to the bean

e) Lifecycle management of the bean

f) Database-connection pooling

g) Instance pooling for the bean

Database System-I

1.What is foreign Key? What is its purpose?

A non key attribute, whose value are derived from the primary key of some other table, is known as foreign key in the current table.The table in which this non-key attribute i.e. foreign key attribute exists, is called a foreign table.

2.Define the terms  Tuple and  Attribute

Tuples: The rows of tables (relations) are generally referred to as tuples. Attribute: The columns of tables are generally referred to as attribute.

3.What do you understand by the terms Cardinality and Degree of the table?

Degree: The number of attributes in a relation determines the degree of a relation. A relation having 3 attributes is said to be a relation of degree 3.

Cardinality: The number of rows in a relation is known as Cardinality.

4.What is the main function of DBA.

The DBA must be a manager, more than a technician-seeking to meet the needs of people who use the data. Since many user may share the same data resource, the DBA must be prepared to meet the need and objective.

5.Write a query on the customers table whose output will exclude all customers with a rating <=100, unless they are located in Shimla.

SELECT *  FROM customers  WHERE rating >100 OR city =’Shimla’ ;

6.Write a query that selects all orders except those zeros or NULLs in  the amount field.

SELECT * FROM Orders  WHERE amt < >0  AND (amt IS NOT NULL) ;

7.Write a query that lists customers in descending order of rating. Output the rating field first, followed by the customer’s name and number.

SELECT rating, cust-name, cust-num FROM customers ORDER BY rating DESC;

8.Write a command that puts the following values, in their given order, into the salesman table: cust-name-Manisha, city-Manali, comm.- NULL, cust-num-1901.

INSERT INTO salesman (city, cust-name, comm.,cust-num)VALUES(‘Manisha’,NULL,1901) ;

9.What are DDL and DML?

The DDL provides statements for the creation and deletion of tables and indexes.

The DML provides statements to enter, update, delete data and perform complex queries on these tables.

10.What is the difference between Where and Having Clause?

The HAVING clause places the condition on group but WHERE clause places the condition on individual rows

11.What do you understand by constraints?

Constraints are used to enforce rules at table level when ever row is inserted, updated/deleted from table.

Constraints can be defined to one of the Two level.

Column Level: Reference to a single column. can be defined any type of integrity.

Table Level: References one or more columns and is defined separately from definition of the columns in the table.

12.Write some features of SQL?

Recovery ad Concurrency:- Concurrency is concerned with the manner in which multiple user operate upon the Database.

Security: The Security can be maintained by view mechanism.

Integrity Constraints-> Integrity constraints are enforced by the system.

13.Write various database objects available in SQL?

Table: A Table is used to store Data

View: A view is the temporary table created using Original table.

Sequence:   Sequences are used to generate Primary key value.

Index:  They are used to improve queries.

Synonym: They give alternative names to objects.     

14.Write the rules to name an objects?

The maximum length must be 30 character long.

The Object name  should not contain quotation mark.

The name must start with letter.

The use of $ and # is discouraged in the object name.

A name must not be a reserved name.

15.What are group Functions?

The aggregate functions are group functions. They return result based on groups of rows. The group functions are

AVG(), COUNT(), MAX(),  MIN(), SUM()

16.What are  column alias?

In many  cases heading table may not be descriptive and hence it difficult to understand. In  such case we use columns alias It will change column heading with column alias.

Computer Network-IV

Q.1 What is protocol? How many types of protocols are there?

Ans. When computers communicate each other, there needs to be a common set of rules and instructions that each computer follows. A specific set of communication rules is called a protocol.

Some protocol: PPP, HTTP, SLIP, FTP, TCP/IP

Q.2 What is the difference between Networking and Remote Networking?

Ans. The main difference between Networking and Remote Networking, is the network which we use in offices or other places locally such LAN or INTERNET and remote networking is one which we use TERMINAL Services to communicate with the remote users such WAN.

Q.3 What is point-to-point protocol?

Ans. A communication protocol used to connect computer to remote networking services include Internet Service Providers. In networking, the Point-to-Point protocol is commonly used to establish a direct connection between two nodes. Its primary use has been to connect computers using a phone line.

Computer Network-III

1. What is packet filter?
Packet filter is a standard router equipped with some extra functionality. The extra functionality allows every incoming or outgoing packet to be inspected. Packets meeting some criterion are forwarded normally. Those that fail the test are dropped.

2. What is traffic shaping?
One of the main causes of congestion is that traffic is often busy. If hosts could be made to transmit at a uniform rate, congestion would be less common. Another open loop method to help manage congestion is forcing the packet to be transmitted at a more predictable rate. This is called traffic shaping.

3. What is multicast routing?
Sending a message to a group is called multicasting, and its routing algorithm is called multicast routing.

Computer Network-II

1. What is Bandwidth?
Every line has an upper limit and a lower limit on the frequency of signals it can carry. This limited range is called the bandwidth.

2. What are the types of Transmission media?
Signals are usually transmitted over some transmission media that are broadly classified in to two categories.
Guided Media:
These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light.
b) Unguided Media:
This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony.

3. What is Project 802?
It is a project started by IEEE to set standards to enable intercommunication between equipment from a variety of manufacturers. It is a way for specifying functions of the physical layer, the data link layer and to some extent the network layer to allow for interconnectivity of major LAN protocols.
It consists of the following:
802.1 is an internetworking standard for compatibility of different LANs and MANs across protocols.
802.2 Logical link control (LLC) is the upper sublayer of the data link layer which is non-architecture-specific, that is remains the same for all IEEE-defined LANs.
Media access control (MAC) is the lower sublayer of the data link layer that contains some distinct modules each carrying proprietary information specific to the LAN product being used. The modules are Ethernet LAN (802.3), Token ring LAN (802.4), Token bus LAN (802.5).
802.6 is distributed queue dual bus (DQDB) designed to be used in MANs.

Computer Fundamental-IX

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1. Which of the following is a web browser?
a. Paint
b. Power point
c. Firefox
d. Word

2. Most of the commonly used personal computers/laptops do not have a command key known as-
a. Turnover
b. Shift
c. Alter
d. Delete

3. What is the full form of USB as used in computer related activities?
a. Universal security Block
b. Ultra serial block
c. United service block
d. Universal serial bus

Computer Fundamental-VIII

1. To indent the first paragraph of your report, you should use this key
a. Space bar
b. Return key
c. Tab key
d. Shift key

2. _______ are distinct items that don’t have much meaning to you in a given context.
a. Fields
b. Data
c. Queries
d. Properties

3. A website address is a unique name that identifies a specific _______ on the web.
a. Web browser
b. PDA
c. Website
d. Link

4. An example of a telecommunications device is a
a. Keyboard
b. Modem
c. Mouse
d. Printer

5. Which is the best definition of a software package?
a. An add-on for your computer such as additional memory
b. A set of computer programs used for a certain function such as word processing
c. A protection you can buy for a computer
d. The box, manual and license agreement that accompany commercial software

Computer Fundamental-VII

1. Special effect used to introduce slides in a presentation are called
a. Effect
b. Custom animation
c. Transition
d. Animation

2. Computers send and receive data in the form of ____________ signals.
a. Analog
b. Digital
c. Modulated
d. All of the above

3. Most World Wide Web pages contain commands in the language.
a. NIH
b. URL
c. HTML
d. IRC

4. _____________ are graphical objects used to represent commonly used application.
a. GUI
b. Drivers
c. Windows
d. Icons

5. Which of the following operating systems is not owned and licensed by a company?
a. Unix
b. Linux
c. Windows 2000
d. Mac

6. In any window, the maximize button, the minimize button and the close button appears on
a. the title bar
b. menu bar
c. status bar
d. tool bar

7. Which is the slowest internet connection service?
a. Digital subscriber line
b. T1
c. Dial up service
d. Cable modem

8. Every component of your computer is either
a. Software of CPU/RAM
b. Hardware or software
c. Application software or system software
d. Input devices or output devices

9. Checking that a pin code number is valid before it is entered into the system in an example of
a. Error connection
b. Backup and recovery
c. Data preparation
d. Data validation

10. A compiler translates higher-level programs into a machine language program, which is called
a. Source code
b. Object code
c. Compiled code
d. Beta code

11. A field that uniquely identifies which person, thing or event the recode describes is a
a. File
b. Data
c. Field
d. Key

12. The ability to find an individual item in a file immediately
a. Sequential access
b. File allocation table
c. Direct access
d. Directory

13. Computers connected to a LAN can
a. Run faster
b. Go on line
c. Email
d. Share information and/or share devices

14. A CD-RW disk
a. Has a faster access than an internal disk
b. Is a form of optical disk, so it an only be written once
c. Holds less data than a floppy disk
d. Can be erased and rewritten

15. The two major categories of software include
a. Operating system and utility
b. Personal productivity and system
c. System and application
d. System and utility

16. Windows 95, windows 98 and windows NT are known as
a. Processors
b. Domain names
c. Modems
d. Operating system

17. Information on a computer is stored as
a. Analog data
b. Digital data
c. Modem data
d. Watts data

18. To take information from one source and bring it to your computer is referred to as
a. Upload
b. Download
c. Transfer
d. De-link

19. A program that works like a calculator for keeping track of money and making budgets
a. Calculator
b. Keyboard
c. Spreadsheets
d. Scholastic

20. Each box in a spreadsheet is called
a. Cell
b. Empty space
c. Record
d. Field
__________________________________________________________________________________

Computer Fundamental-VI

1. What type of program controls the various computer parts and allows the user to interact with the computer?
a. Utility software
b. Operating system
c. Word processing software
d. Database program

2. What is the term for unsolicited email?
a. Spam
b. Usenet
c. Backbone
d. Flaming

3. What is backup?
a. Adding more components to your network
b. Protecting data by copying it from the original source to a different destination
c. Filtering old data from the new data
d. Accessing data on tape

Computer Fundamental-V

1. How many options does a binary choice offer?
a. One
b. Two
c. It depends on the amount of memory in the computer
d. It depends on the speed of the computer’s processor

Computer Fundamental-IV

1. The component is required to process data into information and consists of integrated circuits-
a. Hard disk
b. RAM
c. ROM
d. CPU

Operating System-IV

1. Describe the Buddy system of memory allocation.

Free memory is maintained in linked lists, each of equal sized blocks. Any such block is of size 2^k. When some memory is required by a process, the block size of next higher order is chosen, and broken into two. Note that the two such pieces differ in address only in their kth bit. Such pieces are called buddies. When any used block is freed, the OS checks to see if its buddy is also free. If so, it is rejoined, and put into the original free-block linked-list.

Operating System-III

1. What is an Operating System (OS)?

An operating system is basically software that makes everything in the computer work together smoothly and efficiently. Basically, it controls the "overall" activity of a computer.

Operating systems have three basic jobs they must do:

•Control Hardware - The operating system controls all the parts of the computer and attempts to get everything working together.

•Run Applications - Another job the OS does is run application software. This would include Microsoft Office, WinZip, games, etc.

•Manage Data and Files - The OS makes it easy for you to organize your computer. Through the OS you are able to do a number of things to data including copy, move, delete, and rename it. This makes it much easier to find and organize what you have.

Operating System-II

1. What is DRAM? In which form does it store data? - DRAM is not the best, but it’s cheap, does the job, and is available almost everywhere you look. DRAM data resides in a cell made of a capacitor and a transistor. The capacitor tends to lose data unless it’s recharged every couple of milliseconds, and this recharging tends to slow down the performance of DRAM compared to speedier RAM types.

UNIX O/S Tutorial-III

1. What is the difference between Swapping and Paging?
Swapping:
Whole process is moved from the swap device to the main memory for execution. Process size must be less than or equal to the available main memory. It is easier to implementation and overhead to the system. Swapping systems does not handle the memory more flexibly as compared to the paging systems.
Paging:

UNIX O/S Tutorial-II

1. Brief about the initial process sequence while the system boots up.
While booting, special process called the 'swapper' or 'scheduler' is created with Process-ID 0. The swapper manages memory allocation for processes and influences CPU allocation. The swapper inturn creates 3 children:
the process dispatcher,
vhand and
dbflush
with IDs 1,2 and 3 respectively.
This is done by executing the file /etc/init. Process dispatcher gives birth to the shell. Unix keeps track of all the processes in an internal data structure called the Process Table (listing command is ps -el).

Computer System & Architecture

1. Fetch and decode are associated with the
a. I-Cycle
b. E-Cycle
c. Expansion slot
d. Expansion card

Computer Fundamental-III

1. ____________ is when the more power-hungry components, such as the monitor and the hard drive, are put in idle.
a. Hibernation
b. Power down
c. Standby mode
d. The shutdown procedure

Computer Fundamental-II

1. What menu is selected to cut, copy and paste?
a. File
b. Tools
c. Special
d. Edit

Computer Fundamental-I

1. What menu is selected to print?
a. Edit
b. Special
c. File
d. Tools

Difference between C/C++ and Java

1. A Java string is not implemented as a null-terminated array of characters as it is in C and C++.

2. Most of the Java operators work much the same way as their C/C++ equivalents except for the addition of two new operators, >>> and ^.

3. The comparison operators in Java return a Boolean true or false but not the integer one or zero.

4. The modulo division may be applied to floating point values in Java. This is not permitted in C/C++.

5. The control variable declared in for loop is visible only within the scope of the loop. But in C/C++, it is visible even after the loop is exited.

6. Methods cannot be declared with an explicitly void argument list, as done in C++.

7. Java methods must be defined within the class. Separate definition is not supported.

8. Unlike C/C++, Java checks the range of every subscript and generates an error message when it is violated.

9. Java does not support the destructor function. Instead, it uses the finalize method to restore the memory.

10. Java does not support multiple inheritance.

11. C++ has no equivalent to the finally block of Java.

12. Java is more strictly typed than C/C++ language. For example, in Java, we cannot assign a floating point value to an integer (without explicit type casting).

13. Unlike C/C++ which allows the size of an integer to vary based on the execution environment, Java data type have strictly defined range and does not change with the environment.

14. Java does not support pointers.

15. Java supports labeled break and labeled continue statement.

break has been designed for use only when some sort of special situation occurs. It should not be used to provide the normal means by which a loop is terminated.

16. The use of final to a variable is similar to the use of const in C/C++.

17. Overridden methods in Java are similar to virtual functions in C++.

18. Java does not have a generalized console input method that parallels the scanf in C or cin in C++.

19. Integer types are always signed in Java. There are no unsigned qualifiers.

20. Java does not define escape codes for vertical tab and the bell character.

21. In Java multidimensional arrays are created as arrays. We can define variable size array of arrays.

POINTS TO REMEMBER

• Difference Between Application & Web Server
• Difference between JAVA & .NET technology
• Remember the points about Java
• Difference between C/C++ & Java

Points to remember about Java

1. It is important that the name of the file match the name of the class and the extension be .java.

2. All functions (methods) in Java must be of some class.

3. Member functions are called methods in Java.

4. Creating two methods woth the same name but different arguements is called method overloading.

5. Method overloading allows set to methods with very similar purpose to be given the same name.

6. When a method makes an unqualified reference to another member of the same class, there is an implicit r reference to this object.

7. Java does not provide a default constructor of the class defines a constructor of its own.

8. When present, package must be the first noncomment statement in the file.

9. The import statement must follow the package statment but must also precede all other noncomment statements.

10. The full method or class name, including the package name, must be used when two imported packages contain a method or class with the same name.

11. Due to security reasons, it is not possible to perform file I/O operations from an applet.

12. When a simple type is passed to a method, it is dine by use of call-by-value. Objects are passed by use of call-by-reference.

13. It is illegal to refer to any instance variables inside of a static method.

14. All command-line arguements are passed as strings. We must therefore convert numeric values to their original forms manually.

15. A class member declared as private will remain private to its class. It is not accessible by any code outside its class, including subclasses.

16. The star form of import statement may increase compile time. It will be good practice to explicitly name the classes that we want to use rather than importing whole packages.

17. Interfaces add most of the functionality that is require for many applications which would normally require the use of multiple inheritance in C++.

18. When we implement an interface method, it must be declared as public.

19. If a finally block is associated with a try, the finally will be executed upon conclusion of the try.

20. Java uses pointers (addresses) intenally to store reference to objects, and for elements of any array of objects, However, these pointers are not available for use by programmers.

21. We cannot overload methods with differences only in their return type.

22. When a method with the same signature occurs in both the super class and its subclass, the method in the subclass overrides the method in he super class.

23. Every constructors must invoke its super class constructor in its first statement. Otherwise, the default constructor of the super class will be called.

24. A class marked as final cannot be inherited.

25. A method marked final cannot be overridden.

26. Subclasses of an abstract class that do not provide an implementation of an abstract method, are also abstract.