Windows Applications.

1.The code in a finally clause will never fail to execute, right?

ANSWER
Using System.exit(1); in try block will not allow finally code to execute.

2.What Class.forName will do while loading drivers?

ANSWER
It is used to create an instance of a driver and register it with the DriverManager. When you have loaded a driver, it is available for making a connection with a DBMS.

3.What information is needed to create a TCP Socket?

ANSWER
The Local System?s IP Address and Port Number. And the Remote System’s IPAddress and Port Number.

4.Why does JComponent have add() and remove() methods but Component does not?

ANSWER
because JComponent is a subclass of Container, and can contain other components and jcomponents

5.What is the final keyword denotes?

ANSWER
final keyword denotes that it is the final implementation for that method or variable or class. You can’t override that method/variable/class any more.

6.What is DriverManager?

ANSWER
The basic service to manage set of JDBC drivers.

7.What are the different identifier states of a Thread?

ANSWER
The different identifiers of a Thread are: R - Running or runnable thread, S - Suspended thread, CW - Thread waiting on a condition variable, MW - Thread waiting on a monitor lock, MS - Thread suspended waiting on a monitor lock

8.What is a native method?

ANSWER
What is a native method?

9.What is the difference between this () and super ()?

ANSWER
This () can be used to invoke a constructor of the same class whereas super() can be used to invoke a super class constructor.

10.What must a class do to implement an interface?

ANSWER
It must provide all of the methods in the interface and identify the interface in its implements clause.

11.What value does read() return when it has reached the end of a file?

ANSWER
The read() method returns -1 when it has reached the end of a file.

12.What is the difference between the Reader/Writer class hierarchy and the InputStream/ OutputStream class hierarchy?

ANSWER
The Reader/Writer class hierarchy is character-oriented, and the InputStream/OutputStream class hierarchy is byte-oriented.

13.What is a package?

ANSWER
A package is a collection of classes and interfaces that provides a high-level layer of access protection and name space management.

14.What is the difference between process and thread?

ANSWER
Process is a program in execution whereas thread is a separate path of execution in a program

15.What is the difference between exception and error?

ANSWER
The exception class defines mild error conditions that your program encounters. Exceptions can occur when trying to open the file, which does not exist, the network connection is disrupted, operands being manipulated are out of prescribed ranges, the class file you are interested in loading is missing. The error class defines serious error conditions that you should not attempt to recover from. In most cases it is advisable to let the program terminate when such an error is encountered.

16.What is source and listener?

ANSWER
Source: A source is an object that generates an event. This occurs when the internal state of that object changes in some way. Listener: A listener is an object that is notified when an event occurs. It has two major requirements. First, it must have been registered with one or more sources to receive notifications about specific types of events. Second, it must implement methods to receive and process these notifications.

17.What is adapter class?

ANSWER
An adapter class provides an empty implementation of all methods in an event listener interface. Adapter classes are useful when you want to receive and process only some of the events that are handled by a particular event listener interface. You can define a new class to act listener by extending one of the adapter classes and implementing only those events in which you are interested. For example, the MouseMotionAdapter class has two methods, mouseDragged()and mouseMoved(). The signatures of these empty are exactly as defined in the MouseMotionListener interface. If you are interested in only mouse drag events, then you could simply extend MouseMotionAdapter and implement mouseDragged() .

18.What is meant by controls and what are different types of controls in AWT?

ANSWER
Controls are components that allow a user to interact with your application and the AWT supports the following types of controls: Labels, Push Buttons, Check Boxes, Choice Lists, Lists, Scrollbars, and Text Components. These controls are subclasses of Component.

19.What is the difference between choice and list?

ANSWER
A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices and only one item may be selected from a choice. A List may be displayed in such a way that several list items are visible and it supports the selection of one or more list items.

20.What is the difference between scrollbar and scrollpane?

ANSWER
A Scrollbar is a Component, but not a Container whereas Scrollpane is a Conatiner and handles its own events and perform its own scrolling.

21.What is a layout manager and what are different types of layout managers available in java AWT?

ANSWER
A layout manager is an object that is used to organize components in a container. The different layouts are available are FlowLayout, BorderLayout, CardLayout, GridLayout and GridBagLayout.

22.How are the elements of different layouts organized?

ANSWER
FlowLayout: The elements of a FlowLayout are organized in a top to bottom, left to right fashion. BorderLayout: The elements of a BorderLayout are organized at the borders (North, South, East and West) and the center of a container. CardLayout: The elements of a CardLayout are stacked, on top of the other, like a deck of cards. GridLayout: The elements of a GridLayout are of equal size and are laid out using the square of a grid. GridBagLayout: The elements of a GridBagLayout are organized according to a grid. However, the elements are of different size and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.

23.Which containers use a Border layout as their default layout?

ANSWER
Window, Frame and Dialog classes use a BorderLayout as their layout.

24.Which containers use a Flow layout as their default layout?

ANSWER
Panel and Applet classes use the FlowLayout as their default layout.

25.What is a stream and what are the types of Streams and classes of the Streams?

ANSWER
A Stream is an abstraction that either produces or consumes information. There are two types of Streams and they are: Byte Streams: Provide a convenient means for handling input and output of bytes. Character Streams: Provide a convenient means for handling input & output of characters. Byte Streams classes: Are defined by using two abstract classes, namely InputStream and OutputStream. Character Streams classes: Are defined by using two abstract classes, namely Reader and Writer.

26.What are Vector, Hashtable, LinkedList and Enumeration?

ANSWER
Vector: The Vector class provides the capability to implement a growable array of objects. Hashtable: The Hashtable class implements a Hashtable data structure. A Hashtable indexes and stores objects in a dictionary using hash codes as the object’s keys. Hash codes are integer values that identify objects. LinkedList: Removing or inserting elements in the middle of an array can be done using LinkedList. A LinkedList stores each object in a separate link whereas an array stores object references in consecutive locations. Enumeration: An object that implements the Enumeration interface generates a series of elements, one at a time. It has two methods, namely hasMoreElements() and nextElement(). HasMoreElemnts() tests if this enumeration has more elements and nextElement method returns successive elements of the series.

27.What is the difference between an applet and a servlet?

ANSWER
a) Servlets are to servers what applets are to browsers. b) Applets must have graphical user interfaces whereas servlets have no graphical user interfaces.