52) What is an event and what are the models available for event handling?
Ans: An event is an event object that describes a state of change in a source. In other words, event occurs when an action is generated, like pressing button, clicking mouse, selecting a list, etc.
There are two types of models for handling events and they are:
a) event-inheritance model and b) event-delegation model
53) What are the advantages of the event-delegation model over the event-inheritance model?
Ans: The event-delegation model has two advantages over the event-inheritance model. They are:
a)It enables event handling by objects other than the ones that generate the events. This allows a clean separation between a component’s design and its use.
b)It performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to be repeatedly process unhandled events as is the case of the event-inheritance.
54)What is source and listener ?
Ans: 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.
55) What is adapter class?
Ans: 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( ) .
56)What is meant by controls and what are different types of controls in AWT?
Ans: 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, Text Components.These controls are subclasses of Component.
57) What is the difference between choice and list?
Ans: 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.
58) What is the difference between scrollbar and scrollpane?
Ans: A Scrollbar is a Component, but not a Container whereas Scrollpane is a Conatiner and handles its own events and perform its own scrolling.
59) What is a layout manager and what are different types of layout managers available in java.awt?
Ans: 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,Null layout/Custom layout
60) How are the elements of different layouts organized?
Ans: 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.
61) Which containers use a Border layout as their default layout?
Ans: Window, Frame and Dialog classes use a BorderLayout as their layout.
62) Which containers use a Flow layout as their default layout?
Ans: Panel and Applet classes use the FlowLayout as their default layout
64) What are Vector, Hashtable, LinkedList and Enumeration?
Ans: 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.
65) What is the difference between set and list?
Ans: Set stores elements in an unordered way but does not contain duplicate elements, whereas list stores elements in an ordered way but may contain duplicate elements.
56. Drag and Drop API consist of java.awt.dnd package - False
49.Super class of TextArea and TextField is TextComponent.
51. GridBagConstraints class helps in positioning of parameters of a component within an object laidout using GridBagLayout.
53. EventDelegation model was introduced by JDK 1.1 - False
9. What is the preferred size of a component?
The preferred size of a component is the minimum component size that will allow the component to display normally.
10. What method is used to specify a container’s layout?
The setLayout() method is used to specify a container’s layout.
11. Which containers use a FlowLayout as their default layout?
The Panel and Applet classes use the FlowLayout as their default layout.
21. Which method of the Component class is used to set the position andsize of a component?
setBounds()
24. Which java.util classes and interfaces support event handling?
The EventObject class and the EventListener interface support event processing.
42. What is the difference between a MenuItem and a CheckboxMenuItem?
The CheckboxMenuItem class extends the MenuItem class to support a menu item that may be checked or unchecked.
44. What class is the top of the AWT event hierarchy?
The java.awt.AWTEvent class is the highest-level class in the AWT event-class hierarchy.
49. In which package are most of the AWT events that support theevent-delegation model defined?
Most of the AWT-related events of the event-delegation model are defined in the java.awt.event package. The AWTEvent class is defined in the java.awt package.
50. What is the immediate superclass of Menu?
MenuItem
52. Which class is the immediate superclass of the MenuComponent class.
Object
55. Name three subclasses of the Component class.
Box.Filler, Button, Canvas, Checkbox, Choice, Container, Label, List,Scrollbar, or TextComponent
68. Name two subclasses of the TextComponent class.
TextField and TextArea
69. What is the advantage of the event-delegation model over the earlier event-inheritance model?
The event-delegation model has two advantages over the event-inheritance model.First, it enables event handling to be handled by objects other than the ones that generate the events (or their containers). This allows a clean separation between a component’s design and its use. The other advantage of the event-delegation model is that it performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to repeatedly process unhandled events, as is the case of the event-inheritance model.
70. Which containers may have a MenuBar?
Frame
87. What is the difference between a Window and a Frame?
The Frame class extends Window to define a main application window that can have a menu bar.
97. What is the SimpleTimeZone class?
The SimpleTimeZone class provides support for a Gregorian calendar.
98. What is the Map interface?
The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.
100. For which statements does it make sense to use a label?
The only statements for which it makes sense to use a label are those statements that can enclose a break or continue statement.
102. Which TextComponent method is used to set a TextComponent to the read-only state?
setEditable()
103. How are the elements of a CardLayout organized?
The elements of a CardLayout are stacked, one on top of the other, like a deck of cards.
107. What is the relationship between clipping and repainting?
When a window is repainted by the AWT painting thread, it sets the clipping regions to the area of the window that requires repainting.
109. What is the relationship between an event-listener interface and an event-adapter class?
An event-listener interface defines the methods that must be implemented by an event handler for a particular kind of event. An event adapter provides a default implementation of an event-listener interface.
113. What is the highest-level event class of the event-delegation model?
The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy.
114. What event results from the clicking of a button?
The ActionEvent event is generated as the result of the clicking of a button.
115. How can a GUI component handle its own events?
A component can handle its own events by implementing the required event-listener interface and adding itself as its own event listener.
117. How are the elements of a GridBagLayout organized?
The elements of a GridBagLayout are organized according to a grid. However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.
118. What advantage do Java’s layout managers provide over traditional windowing systems?
Java uses layout managers to lay out components in a consistent manner across all windowing platforms. Since Java’s layout managers aren’t tied to absolute sizing and positioning, they are able to accomodate platform-specific differences among windowing systems.
119. What is the Collection interface?
The Collection interface provides support for the implementation of a mathematical bag - an unordered collection of objects that may contain duplicates.
122. What is the difference between the paint() and repaint() methods?
The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread.
129. Which class is the immediate superclass of the Container class?
Component
131. How can the Checkbox class be used to create a radio button?
By associating Checkbox objects with a CheckboxGroup.
137. Name four Container classes.
Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane
138. What is the difference between a Choice and a List?
A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices. Only one item may be selected from a Choice. A List may be displayed in such a way that several List items are visible. A List supports the selection of one or more List items
145. What is the difference between the JDK 1.02 event model and the event-delegation model introduced with JDK 1.1?
The JDK 1.02 event model uses an event inheritance or bubbling approach. In this model, components are required to handle their own events. If they do not handle a particular event, the event is inherited by (or bubbled up to) the component’s container. The container then either handles the event or it is bubbled up to its container and so on, until the highest-level container has been tried.
In the event-delegation model, specific objects are designated as event handlers for GUI components. These objects implement event-listener interfaces.The event-delegation model is more efficient than the event-inheritance model because it eliminates the processing required to support the bubbling of unhandled events.
148. What Checkbox method allows you to tell if a Checkbox is checked?
getState()
151. How are the elements of a GridLayout organized?
The elements of a GridBad layout are of equal size and are laid out using the squares of a grid.
159. What is the purpose of the enableEvents() method?
The enableEvents() method is used to enable an event for a particular object. Normally, an event is enabled when a listener is added to an object for a particular event. The enableEvents() method is used by objects that handle events by overriding their event-dispatch methods.
168. What interface is extended by AWT event listeners?
All AWT event listeners extend the java.util.EventListener interface.
172. What is a layout manager?
A layout manager is an object that is used to organize components in a container.
179. What is the difference between a Scrollbar and a ScrollPane?
A Scrollbar is a Component, but not a Container. A ScrollPane is a Container. A ScrollPane handles its own events and performs its own scrolling.
192. What methods are used to get and set the text label displayed by a Buttonobject?
getLabel() and setLabel()
193. Which Component subclass is used for drawing and painting?
Canvas
Ans: An event is an event object that describes a state of change in a source. In other words, event occurs when an action is generated, like pressing button, clicking mouse, selecting a list, etc.
There are two types of models for handling events and they are:
a) event-inheritance model and b) event-delegation model
53) What are the advantages of the event-delegation model over the event-inheritance model?
Ans: The event-delegation model has two advantages over the event-inheritance model. They are:
a)It enables event handling by objects other than the ones that generate the events. This allows a clean separation between a component’s design and its use.
b)It performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to be repeatedly process unhandled events as is the case of the event-inheritance.
54)What is source and listener ?
Ans: 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.
55) What is adapter class?
Ans: 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( ) .
56)What is meant by controls and what are different types of controls in AWT?
Ans: 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, Text Components.These controls are subclasses of Component.
57) What is the difference between choice and list?
Ans: 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.
58) What is the difference between scrollbar and scrollpane?
Ans: A Scrollbar is a Component, but not a Container whereas Scrollpane is a Conatiner and handles its own events and perform its own scrolling.
59) What is a layout manager and what are different types of layout managers available in java.awt?
Ans: 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,Null layout/Custom layout
60) How are the elements of different layouts organized?
Ans: 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.
61) Which containers use a Border layout as their default layout?
Ans: Window, Frame and Dialog classes use a BorderLayout as their layout.
62) Which containers use a Flow layout as their default layout?
Ans: Panel and Applet classes use the FlowLayout as their default layout
64) What are Vector, Hashtable, LinkedList and Enumeration?
Ans: 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.
65) What is the difference between set and list?
Ans: Set stores elements in an unordered way but does not contain duplicate elements, whereas list stores elements in an ordered way but may contain duplicate elements.
56. Drag and Drop API consist of java.awt.dnd package - False
49.Super class of TextArea and TextField is TextComponent.
51. GridBagConstraints class helps in positioning of parameters of a component within an object laidout using GridBagLayout.
53. EventDelegation model was introduced by JDK 1.1 - False
9. What is the preferred size of a component?
The preferred size of a component is the minimum component size that will allow the component to display normally.
10. What method is used to specify a container’s layout?
The setLayout() method is used to specify a container’s layout.
11. Which containers use a FlowLayout as their default layout?
The Panel and Applet classes use the FlowLayout as their default layout.
21. Which method of the Component class is used to set the position andsize of a component?
setBounds()
24. Which java.util classes and interfaces support event handling?
The EventObject class and the EventListener interface support event processing.
42. What is the difference between a MenuItem and a CheckboxMenuItem?
The CheckboxMenuItem class extends the MenuItem class to support a menu item that may be checked or unchecked.
44. What class is the top of the AWT event hierarchy?
The java.awt.AWTEvent class is the highest-level class in the AWT event-class hierarchy.
49. In which package are most of the AWT events that support theevent-delegation model defined?
Most of the AWT-related events of the event-delegation model are defined in the java.awt.event package. The AWTEvent class is defined in the java.awt package.
50. What is the immediate superclass of Menu?
MenuItem
52. Which class is the immediate superclass of the MenuComponent class.
Object
55. Name three subclasses of the Component class.
Box.Filler, Button, Canvas, Checkbox, Choice, Container, Label, List,Scrollbar, or TextComponent
68. Name two subclasses of the TextComponent class.
TextField and TextArea
69. What is the advantage of the event-delegation model over the earlier event-inheritance model?
The event-delegation model has two advantages over the event-inheritance model.First, it enables event handling to be handled by objects other than the ones that generate the events (or their containers). This allows a clean separation between a component’s design and its use. The other advantage of the event-delegation model is that it performs much better in applications where many events are generated. This performance improvement is due to the fact that the event-delegation model does not have to repeatedly process unhandled events, as is the case of the event-inheritance model.
70. Which containers may have a MenuBar?
Frame
87. What is the difference between a Window and a Frame?
The Frame class extends Window to define a main application window that can have a menu bar.
97. What is the SimpleTimeZone class?
The SimpleTimeZone class provides support for a Gregorian calendar.
98. What is the Map interface?
The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.
100. For which statements does it make sense to use a label?
The only statements for which it makes sense to use a label are those statements that can enclose a break or continue statement.
102. Which TextComponent method is used to set a TextComponent to the read-only state?
setEditable()
103. How are the elements of a CardLayout organized?
The elements of a CardLayout are stacked, one on top of the other, like a deck of cards.
107. What is the relationship between clipping and repainting?
When a window is repainted by the AWT painting thread, it sets the clipping regions to the area of the window that requires repainting.
109. What is the relationship between an event-listener interface and an event-adapter class?
An event-listener interface defines the methods that must be implemented by an event handler for a particular kind of event. An event adapter provides a default implementation of an event-listener interface.
113. What is the highest-level event class of the event-delegation model?
The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy.
114. What event results from the clicking of a button?
The ActionEvent event is generated as the result of the clicking of a button.
115. How can a GUI component handle its own events?
A component can handle its own events by implementing the required event-listener interface and adding itself as its own event listener.
117. How are the elements of a GridBagLayout organized?
The elements of a GridBagLayout are organized according to a grid. However, the elements are of different sizes and may occupy more than one row or column of the grid. In addition, the rows and columns may have different sizes.
118. What advantage do Java’s layout managers provide over traditional windowing systems?
Java uses layout managers to lay out components in a consistent manner across all windowing platforms. Since Java’s layout managers aren’t tied to absolute sizing and positioning, they are able to accomodate platform-specific differences among windowing systems.
119. What is the Collection interface?
The Collection interface provides support for the implementation of a mathematical bag - an unordered collection of objects that may contain duplicates.
122. What is the difference between the paint() and repaint() methods?
The paint() method supports painting via a Graphics object. The repaint() method is used to cause paint() to be invoked by the AWT painting thread.
129. Which class is the immediate superclass of the Container class?
Component
131. How can the Checkbox class be used to create a radio button?
By associating Checkbox objects with a CheckboxGroup.
137. Name four Container classes.
Window, Frame, Dialog, FileDialog, Panel, Applet, or ScrollPane
138. What is the difference between a Choice and a List?
A Choice is displayed in a compact form that requires you to pull it down to see the list of available choices. Only one item may be selected from a Choice. A List may be displayed in such a way that several List items are visible. A List supports the selection of one or more List items
145. What is the difference between the JDK 1.02 event model and the event-delegation model introduced with JDK 1.1?
The JDK 1.02 event model uses an event inheritance or bubbling approach. In this model, components are required to handle their own events. If they do not handle a particular event, the event is inherited by (or bubbled up to) the component’s container. The container then either handles the event or it is bubbled up to its container and so on, until the highest-level container has been tried.
In the event-delegation model, specific objects are designated as event handlers for GUI components. These objects implement event-listener interfaces.The event-delegation model is more efficient than the event-inheritance model because it eliminates the processing required to support the bubbling of unhandled events.
148. What Checkbox method allows you to tell if a Checkbox is checked?
getState()
151. How are the elements of a GridLayout organized?
The elements of a GridBad layout are of equal size and are laid out using the squares of a grid.
159. What is the purpose of the enableEvents() method?
The enableEvents() method is used to enable an event for a particular object. Normally, an event is enabled when a listener is added to an object for a particular event. The enableEvents() method is used by objects that handle events by overriding their event-dispatch methods.
168. What interface is extended by AWT event listeners?
All AWT event listeners extend the java.util.EventListener interface.
172. What is a layout manager?
A layout manager is an object that is used to organize components in a container.
179. What is the difference between a Scrollbar and a ScrollPane?
A Scrollbar is a Component, but not a Container. A ScrollPane is a Container. A ScrollPane handles its own events and performs its own scrolling.
192. What methods are used to get and set the text label displayed by a Buttonobject?
getLabel() and setLabel()
193. Which Component subclass is used for drawing and painting?
Canvas
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.