Java abstract classes and methods
Can anyone please tell me any real time example of abstract classes and methods.
I want to know its real use. If anyone have ever used it for some purpose while programming please do tell me.
Ashu_Web wrote:
No please.. I just want to know if you have used it while programming. Like "an abstract class can be used to put all the common method names in it without having to write actual implementation code."That would describe an Interface better than an abstract class. Abstract classes usually have at least some implementation.
I want to know its usage in programming, not just a definition. I guess you understand what I am looking for.Yes, and I gave you one: java.util.AbstractList. It can be found inside the src.zip in your JDK directory and it is a pretty good example for an abstract class that provides some implementation and defines exactly what is necessary to make a full List implementation.
Similar Messages
-
Dear all Abaper experts,
I am doubt on a abap object program shown as below. It is a ABSTRACT class and method. However, during compiling, an error message is displayed "The abstract method 'WRITE_STATUS' may not be implemented". What does it mean?
REPORT ZOOP_ABSTRACT.
* Class Declaration
CLASS vehicle DEFINITION ABSTRACT.
PUBLIC SECTION.
METHODS: accelerate,
write_status ABSTRACT.
PROTECTED SECTION.
DATA speed TYPE i.
ENDCLASS.
CLASS plane DEFINITION INHERITING FROM vehicle.
PUBLIC SECTION.
METHODS: rise.
PROTECTED SECTION.
DATA altitude TYPE i.
ENDCLASS.
CLASS ship DEFINITION INHERITING FROM vehicle.
ENDCLASS.
* Class Implementation
CLASS vehicle IMPLEMENTATION.
METHOD accelerate.
speed = speed + 1.
ENDMETHOD.
ENDCLASS.
CLASS plane IMPLEMENTATION.
METHOD rise.
altitude = altitude + 1.
ENDMETHOD.
METHOD write_status.
WRITE: / 'Plane speed:', speed.
WRITE: / 'Altitude:', altitude.
ENDMETHOD.
ENDCLASS.
CLASS ship IMPLEMENTATION.
ENDCLASS.
* Global Data
DATA: plane_ref TYPE REF TO plane,
ship_ref TYPE REF TO ship.
* Classical Processing Blocks
START-OF-SELECTION.
CREATE OBJECT: plane_ref,
ship_ref.
CALL METHOD: plane_ref->accelerate,
plane_ref->rise,
plane_ref->write_status,
plane_ref->accelerate,
plane_ref->write_status.
All answers are welcome and appreciate for the help.Hi,
try this code I've rearranged your Class Implementation and just added the foll code;
write_status REDEFINITION in the Definition part of the Subclass.
* Class Declaration
CLASS vehicle DEFINITION ABSTRACT.
PUBLIC SECTION.
METHODS: accelerate,
write_status ABSTRACT.
PROTECTED SECTION.
DATA speed TYPE i.
ENDCLASS.
* Class Implementation
CLASS vehicle IMPLEMENTATION.
METHOD accelerate.
speed = speed + 1.
ENDMETHOD.
ENDCLASS.
CLASS plane DEFINITION INHERITING FROM vehicle.
PUBLIC SECTION.
METHODS: rise,
write_status redefinition.
PROTECTED SECTION.
DATA altitude TYPE i.
ENDCLASS.
CLASS plane IMPLEMENTATION.
METHOD rise.
altitude = altitude + 1.
ENDMETHOD.
METHOD write_status.
WRITE: / 'Plane speed:', speed.
WRITE: / 'Altitude:', altitude.
ENDMETHOD.
ENDCLASS.
CLASS ship DEFINITION INHERITING FROM vehicle.
PUBLIC SECTION.
METHODS: write_status redefinition.
ENDCLASS.
CLASS ship IMPLEMENTATION.
METHOD write_status.
WRITE: / 'In Ship Class.'.
ENDMETHOD.
ENDCLASS.
* Global Data
DATA: plane_ref TYPE REF TO plane,
ship_ref TYPE REF TO ship.
* Classical Processing Blocks
START-OF-SELECTION.
CREATE OBJECT: plane_ref,
ship_ref.
CALL METHOD: plane_ref->accelerate,
plane_ref->rise,
plane_ref->write_status,
plane_ref->accelerate,
plane_ref->write_status,
ship_ref->write_status.
Best Regards,
Sunil. -
Abstract classes and methods with dollar.decimal not displaying correctly
Hi, I'm working on a homework assignment and need a little help. I have two classes, 1 abstract class, 1 extends class and 1 program file. When I run the program file, it executes properly, but the stored values are not displaying correctly. I'm trying to get them to display in the dollar format, but it's leaving off the last 0. Can someone please offer some assistance. Here's what I did.
File 1
public abstract class Customer//Using the abstract class for the customer info
private String name;//customer name
private String acctNo;//customer account number
private int branchNumber;//The bank branch number
//The constructor accepts as arguments the name, acctNo, and branchNumber
public Customer(String n, String acct, int b)
name = n;
acctNo = acct;
branchNumber = b;
//toString method
public String toString()
String str;
str = "Name: " + name + "\nAccount Number: " + acctNo + "\nBranch Number: " + branchNumber;
return str;
//Using the abstract method for the getCurrentBalance class
public abstract double getCurrentBalance();
}file 2
public class AccountTrans extends Customer //
private final double
MONTHLY_DEPOSITS = 100,
COMPANY_MATCH = 10,
MONTHLY_INTEREST = 1;
private double monthlyDeposit,
coMatch,
monthlyInt;
//The constructor accepts as arguments the name, acctNo, and branchNumber
public AccountTrans(String n, String acct, int b)
super(n, acct, b);
//The setMonthlyDeposit accepts the value for the monthly deposit amount
public void setMonthlyDeposit(double deposit)
monthlyDeposit = deposit;
//The setCompanyMatch accepts the value for the monthly company match amount
public void setCompanyMatch(double match)
coMatch = match;
//The setMonthlyInterest accepts the value for the monthly interest amount
public void setMonthlyInterest(double interest)
monthlyInt = interest;
//toString method
public String toString()
String str;
str = super.toString() +
"\nAccount Type: Hybrid Retirement" +
"\nDeposits: $" + monthlyDeposit +
"\nCompany Match: $" + coMatch +
"\nInterest: $" + monthlyInt;
return str;
//Using the getter method for the customer.java fields
public double getCurrentBalance()
double currentBalance;
currentBalance = (monthlyDeposit + coMatch + monthlyInt) * (2);
return currentBalance;
}File 3
public static void main(String[] args)
//Creates the AccountTrans object
AccountTrans acctTrans = new AccountTrans("Jane Smith", "A123ZW", 435);
//Created to store the values for the MonthlyDeposit,
//CompanyMatch, MonthlyInterest
acctTrans.setMonthlyDeposit(100);
acctTrans.setCompanyMatch(10);
acctTrans.setMonthlyInterest(5);
DecimalFormat dollar = new DecimalFormat("#,##0.00");
//This will display the customer's data
System.out.println(acctTrans);
//This will display the current balance times 2 since the current
//month is February.
System.out.println("Your current balance is $"
+ dollar.format(acctTrans.getCurrentBalance()));
}Get a hair cut!
h1. The Ubiquitous Newbie Tips
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System.out.println("Your momma!); // <<<< ERROR 1
- Note that error messages are rendered basically useless if the code has been
modified AT ALL since the error message was produced.
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If you (the newbie) have covered these bases *you deserve, and can therefore expect, GOOD answers!*
h1. The pledge!
We the New To Java regulars do hereby pledge to refrain from flaming anybody, no matter how gumbyish the question, if the OP has demonstrably tried to cover these bases. The rest are fair game. -
Why does this abstract class and method work without implement it?
hi,
I have seen many times that in some examples that there are objects made from abstract classes directly. However, in all books, manual and tutorials that I've read explain that we MUST implement those methods in a subclass.
An example of what I'm saying is the example code here . In a few words that example makes Channels (java.nio.channel) and does operations with them. My problem is in the class to make this channels, because they used the ServerSockeChannel class and socket() method directly despite they are abstracts.
// Create a new channel: if port == 0, FileChannel on /dev/tty, else
// a SocketChannel from the first accept on the given port number
private static ByteChannel newChannel (int netPort)
throws Exception
if (netPort == 0) {
FileInputStream fis = new FileInputStream ("/dev/tty");
return (fis.getChannel());
} else {
//CONFLICT LINES
ServerSocketChannel ssc = ServerSocketChannel.open(); //<--I have never thought do that!! Anyway, how it is static method may work.
ssc.socket().bind (new InetSocketAddress (netPort)); //<--but here, this method (socket) is abstract. WHY RETURN A SOCKET???????? this mehod should be empty by default.
System.out.print ("Waiting for connection on port "
+ netPort + "...");
System.out.flush();
ByteChannel channel = ssc.accept();
ssc.close();
System.out.println ("Got it");
return (channel);
} I test this code and works fine. So why can it be??
Also, I read that the abstract classes can't have static methods. Is it true???
Please Help!!
PS: i have seen this kind of code many times. So i feel that I don't understand how its really the abstract methods are made.
PS2: I understand that obviously you don't do something like this: *"obj = new AbstractClass(); "*. I dont understand how it could be: ServerSocketChannel ssc = ServerSocketChannel.open(); and the compiler didn't warn.molavec wrote:
ServerSocketChannel ssc = ServerSocketChannel.open(); //<--I have never thought do that!! Anyway, how it is static method may work.
The static method creates an instance of a class which extends ServerSocketChannel, but is actually another non-abstract class.I thought that, but reading the documentation I saw that about open() method:
Opens a server-socket channel.
The new channel is created by invoking the openServerSocketChannel method of the system-wide default SelectorProvider object.
The new channel's socket is initially unbound; it must be bound to a specific address via one of its socket's bind methods before connections can be accepted.
...and the problem is the same openServerSocketChannel is abstract, so i don't understand how it could return a ServerSocketChannel.There is a concrete implementation class that has implemented that method.
I guess that really the open() method use a SelectorProvider's subclase but it doesn't appear in the doc.It doesn't need to. First, you don't care about those implementation details, and second, you know that if the class is abstract, it must use some concrete subclass.
Ok, I speak Spanish by default (<-- this sounds like "I am a machine", ^_^' ). So, I didn't know how to say that the method would be {}. Is there a way to say that?? I recommendable for me to know, for the future questions o answers.Not sure what you're saying here. But the other respondent was trying to explain to you the difference between an abstract method and an empty method.
// abstract method
public abstract void foo();
// empty method
public void bar() {
Which class does extend ServerSocketChannel? I can not see it.It may be a package-private class or a private nested class. There's no need to document that specific implementation, since you never need to use it directly. -
Hi all,
I want to appear for SCJP exam and studying for the same ,
Can anyone tell whether concrete methods in an abstract class can be overridden by its subclass or not ... ???
Thanks in advance ,
SuvoHai
Actually the overridden concept is supported when the methods are default, protected, public with some constraints, not only when they are protected and public.
The access specifier in the overriding method (in the derived class) should not be more limiting than that of the overriden method (in the base class). This means that if the access specifier for base class method is protected then the access specifier for the derived class method should not be default or private but can be protected, public. The order of increasing visibility of various specifiers is:
default
protected
public
Thanks,
Hari
Edited by: Hari on Jun 3, 2011 8:45 PM -
What is the advantage of abstract class and method???
hi,
* Why a class is declared as abstract???
* What is the use of declaring a class as abstract???
* At what situation abstract class will be used???Thanks
JavaImranTo save you from the wrath of the Java experts on this forum, allow me as a relatively new Java user to advise you: do NOT post homework problems here; you're just going to get told to go google the answer. Which would be a good move on your part. Especially since I found the answer to your questions by googling them myself.
-
Call Java Class and Methods from ABAP
Hi
I install de JCo, But how i can call java class and methods from ABAP?. somebody has an example?
The tutorial say that's is possible, but don't explain how do that?
Thanks.
Angel G. HurtadoIf you need only simple java program, you do not need to install JCo. The following codes can call java class.
DATA: COMMAND TYPE STRING VALUE 'C:\j2sdk1.4.2_08\bin\java',
DIR TYPE STRING VALUE D:\eclipse\workspace',
PARAMETER TYPE STRING VALUE 'Helloworld'. "here the name of your java program
CALL METHOD CL_GUI_FRONTEND_SERVICES=>EXECUTE
EXPORTING
APPLICATION = COMMAND
PARAMETER = PARAMETER
DEFAULT_DIRECTORY = DIR
MAXIMIZED =
MINIMIZED = 'X' "If you need the DOS window to be minimized
EXCEPTIONS
CNTL_ERROR = 1
ERROR_NO_GUI = 2
BAD_PARAMETER = 3
FILE_NOT_FOUND = 4
PATH_NOT_FOUND = 5
FILE_EXTENSION_UNKNOWN = 6
ERROR_EXECUTE_FAILED = 7
OTHERS = 8.
Tell me if it works.
Nuno. -
Difference between abstract class and the normal class
Hi...........
can anyone tell me use of abstract class instead of normal class
The main doubt for me is...
1.why we are defining the abstract method in a abstract class and then implementing that in to the normal class.instead of that we can straight way create and implement the method in normal class right...../Class vs. interface
Some say you should define all classes in terms of interfaces, but I think recommendation seems a bit extreme. I use interfaces when I see that something in my design will change frequently.
For example, the Strategy pattern lets you swap new algorithms and processes into your program without altering the objects that use them. A media player might know how to play CDs, MP3s, and wav files. Of course, you don't want to hardcode those playback algorithms into the player; that will make it difficult to add a new format like AVI. Furthermore, your code will be littered with useless case statements. And to add insult to injury, you will need to update those case statements each time you add a new algorithm. All in all, this is not a very object-oriented way to program.
With the Strategy pattern, you can simply encapsulate the algorithm behind an object. If you do that, you can provide new media plug-ins at any time. Let's call the plug-in class MediaStrategy. That object would have one method: playStream(Stream s). So to add a new algorithm, we simply extend our algorithm class. Now, when the program encounters the new media type, it simply delegates the playing of the stream to our media strategy. Of course, you'll need some plumbing to properly instantiate the algorithm strategies you will need.
This is an excellent place to use an interface. We've used the Strategy pattern, which clearly indicates a place in the design that will change. Thus, you should define the strategy as an interface. You should generally favor interfaces over inheritance when you want an object to have a certain type; in this case, MediaStrategy. Relying on inheritance for type identity is dangerous; it locks you into a particular inheritance hierarchy. Java doesn't allow multiple inheritance, so you can't extend something that gives you a useful implementation or more type identity.
Interface vs. abstract class
Choosing interfaces and abstract classes is not an either/or proposition. If you need to change your design, make it an interface. However, you may have abstract classes that provide some default behavior. Abstract classes are excellent candidates inside of application frameworks.
Abstract classes let you define some behaviors; they force your subclasses to provide others. For example, if you have an application framework, an abstract class may provide default services such as event and message handling. Those services allow your application to plug in to your application framework. However, there is some application-specific functionality that only your application can perform. Such functionality might include startup and shutdown tasks, which are often application-dependent. So instead of trying to define that behavior itself, the abstract base class can declare abstract shutdown and startup methods. The base class knows that it needs those methods, but an abstract class lets your class admit that it doesn't know how to perform those actions; it only knows that it must initiate the actions. When it is time to start up, the abstract class can call the startup method. When the base class calls this method, Java calls the method defined by the child class. -
What is the difference between abstract class and class in java?
arcadesstuff wrote:
Abstract class: a class that contains at least one abstract method. As has already been mentioned, abstract classes need not contain any methods at all. Have a look at the abstract class you posted; it's still abstract, though it contains no abstract methods. Note that if one declares any method of a class abstract, the class itself must be declared abstract as well.
When you implement the abstract class Animal, you will have to write the code of those two abstract methods from above.Your example contains no abstract methods. Abstract methods must be marked with the keyword "abstract".
~ -
What is the difference between Abstract class and Interface ?
Hi,
Could u plz tell me the difference between Abstract class and Interface?
Thanks in advance.
GopiLots.
An abstract class can contain some method implementations, or indeed all the method implementations. It may contain methods with all the various access modifiers. It cannot be instantiated. A class may inherit from only a single abstract class.
An interface contains only public method stubs and constants. A class may implement multiple interfaces. An interface cannot (obviously) be instantiated.
Abstract classes are particularly useful when you need to provide a semi-complete implementation for reuse. Interfaces are used more like types.
Look at java.util.* for some good examples of the use of both. -
What is the diff b/w Abstract class and an interface ?
Hey
I am always confused as with this issue : diff b/w Abstract class and an interface ?
Which is more powerful in what situation.
Regards
VinayHi, Don't worry I am teach you
Abstract class and Interface
An abstract class can have instance methods that implement a default behavior. An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract. An interface has all public members and no implementation. An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.
Edited by SASIKUMARA
SIT INNOVATIONS- Chennai
Message was edited by:
sasikumara
Message was edited by:
sasikumara -
Could you please send me the material Opps concepts Classes and Methods
Hi Experts,
I am working on Opps concepts.I am new to this concept.
Could you please send me the detailed presentation on Abap oops.
Thanks inadvance,
Regards,
Rekha.Hi this will help u.
OOPs ABAP uses Classes and Interfaces which uses Methods and events.
If you have Java skills it is advantage for you.
There are Local classes as well as Global Classes.
Local classes we can work in SE38 straight away.
But mostly it is better to use the Global classes.
Global Classes or Interfaces are to be created in SE24.
SAP already given some predefined classes and Interfaces.
This OOPS concepts very useful for writing BADI's also.
So first create a class in SE 24.
Define attributes, Methods for that class.
Define parameters for that Method.
You can define event handlers also to handle the messages.
After creation in each method write the code.
Methods are similar to ABAP PERFORM -FORM statements.
After the creation of CLass and methods come to SE38 and create the program.
In the program create a object type ref to that class and with the help of that Object call the methods of that Class and display the data.
Example:
REPORT sapmz_hf_alv_grid .
Type pool for icons - used in the toolbar
TYPE-POOLS: icon.
TABLES: zsflight.
To allow the declaration of o_event_receiver before the
lcl_event_receiver class is defined, decale it as deferred in the
start of the program
CLASS lcl_event_receiver DEFINITION DEFERRED.
G L O B A L I N T E R N A L T A B L E S
*DATA: gi_sflight TYPE STANDARD TABLE OF sflight.
To include a traffic light and/or color a line the structure of the
table must include fields for the traffic light and/or the color
TYPES: BEGIN OF st_sflight.
INCLUDE STRUCTURE zsflight.
Field for traffic light
TYPES: traffic_light TYPE c.
Field for line color
types: line_color(4) type c.
TYPES: END OF st_sflight.
TYPES: tt_sflight TYPE STANDARD TABLE OF st_sflight.
DATA: gi_sflight TYPE tt_sflight.
G L O B A L D A T A
DATA: ok_code LIKE sy-ucomm,
Work area for internal table
g_wa_sflight TYPE st_sflight,
ALV control: Layout structure
gs_layout TYPE lvc_s_layo.
Declare reference variables to the ALV grid and the container
DATA:
go_grid TYPE REF TO cl_gui_alv_grid,
go_custom_container TYPE REF TO cl_gui_custom_container,
o_event_receiver TYPE REF TO lcl_event_receiver.
DATA:
Work area for screen 200
g_screen200 LIKE zsflight.
Data for storing information about selected rows in the grid
DATA:
Internal table
gi_index_rows TYPE lvc_t_row,
Information about 1 row
g_selected_row LIKE lvc_s_row.
C L A S S E S
CLASS lcl_event_receiver DEFINITION.
PUBLIC SECTION.
METHODS:
handle_toolbar FOR EVENT toolbar OF cl_gui_alv_grid
IMPORTING
e_object e_interactive,
handle_user_command FOR EVENT user_command OF cl_gui_alv_grid
IMPORTING e_ucomm.
ENDCLASS.
CLASS lcl_event_receiver IMPLEMENTATION
CLASS lcl_event_receiver IMPLEMENTATION.
METHOD handle_toolbar.
Event handler method for event toolbar.
CONSTANTS:
Constants for button type
c_button_normal TYPE i VALUE 0,
c_menu_and_default_button TYPE i VALUE 1,
c_menu TYPE i VALUE 2,
c_separator TYPE i VALUE 3,
c_radio_button TYPE i VALUE 4,
c_checkbox TYPE i VALUE 5,
c_menu_entry TYPE i VALUE 6.
DATA:
ls_toolbar TYPE stb_button.
Append seperator to the normal toolbar
CLEAR ls_toolbar.
MOVE c_separator TO ls_toolbar-butn_type..
APPEND ls_toolbar TO e_object->mt_toolbar.
Append a new button that to the toolbar. Use E_OBJECT of
event toolbar. E_OBJECT is of type CL_ALV_EVENT_TOOLBAR_SET.
This class has one attribute MT_TOOLBAR which is of table type
TTB_BUTTON. The structure is STB_BUTTON
CLEAR ls_toolbar.
MOVE 'CHANGE' TO ls_toolbar-function.
MOVE icon_change TO ls_toolbar-icon.
MOVE 'Change flight' TO ls_toolbar-quickinfo.
MOVE 'Change' TO ls_toolbar-text.
MOVE ' ' TO ls_toolbar-disabled.
APPEND ls_toolbar TO e_object->mt_toolbar.
ENDMETHOD.
METHOD handle_user_command.
Handle own functions defined in the toolbar
CASE e_ucomm.
WHEN 'CHANGE'.
PERFORM change_flight.
LEAVE TO SCREEN 0.
ENDCASE.
ENDMETHOD.
ENDCLASS.
S T A R T - O F - S E L E C T I O N.
START-OF-SELECTION.
SET SCREEN '100'.
*& Module USER_COMMAND_0100 INPUT
MODULE user_command_0100 INPUT.
CASE ok_code.
WHEN 'EXIT'.
LEAVE TO SCREEN 0.
ENDCASE.
ENDMODULE. " USER_COMMAND_0100 INPUT
*& Module STATUS_0100 OUTPUT
MODULE status_0100 OUTPUT.
DATA:
For parameter IS_VARIANT that is sued to set up options for storing
the grid layout as a variant in method set_table_for_first_display
l_layout TYPE disvariant,
Utillity field
l_lines TYPE i.
After returning from screen 200 the line that was selected before
going to screen 200, should be selected again. The table gi_index_rows
was the output table from the GET_SELECTED_ROWS method in form
CHANGE_FLIGHT
DESCRIBE TABLE gi_index_rows LINES l_lines.
IF l_lines > 0.
CALL METHOD go_grid->set_selected_rows
EXPORTING
it_index_rows = gi_index_rows.
CALL METHOD cl_gui_cfw=>flush.
REFRESH gi_index_rows.
ENDIF.
Read data and create objects
IF go_custom_container IS INITIAL.
Read data from datbase table
PERFORM get_data.
Create objects for container and ALV grid
CREATE OBJECT go_custom_container
EXPORTING container_name = 'ALV_CONTAINER'.
CREATE OBJECT go_grid
EXPORTING
i_parent = go_custom_container.
Create object for event_receiver class
and set handlers
CREATE OBJECT o_event_receiver.
SET HANDLER o_event_receiver->handle_user_command FOR go_grid.
SET HANDLER o_event_receiver->handle_toolbar FOR go_grid.
Layout (Variant) for ALV grid
l_layout-report = sy-repid. "Layout fo report
Setup the grid layout using a variable of structure lvc_s_layo
Set grid title
gs_layout-grid_title = 'Flights'.
Selection mode - Single row without buttons
(This is the default mode
gs_layout-sel_mode = 'B'.
Name of the exception field (Traffic light field) and the color
field + set the exception and color field of the table
gs_layout-excp_fname = 'TRAFFIC_LIGHT'.
gs_layout-info_fname = 'LINE_COLOR'.
LOOP AT gi_sflight INTO g_wa_sflight.
IF g_wa_sflight-paymentsum < 100000.
Value of traffic light field
g_wa_sflight-traffic_light = '1'.
Value of color field:
C = Color, 6=Color 1=Intesified on, 0: Inverse display off
g_wa_sflight-line_color = 'C610'.
ELSEIF g_wa_sflight-paymentsum => 100000 AND
g_wa_sflight-paymentsum < 1000000.
g_wa_sflight-traffic_light = '2'.
ELSE.
g_wa_sflight-traffic_light = '3'.
ENDIF.
MODIFY gi_sflight FROM g_wa_sflight.
ENDLOOP.
Grid setup for first display
CALL METHOD go_grid->set_table_for_first_display
EXPORTING i_structure_name = 'SFLIGHT'
is_variant = l_layout
i_save = 'A'
is_layout = gs_layout
CHANGING it_outtab = gi_sflight.
*-- End of grid setup -
Raise event toolbar to show the modified toolbar
CALL METHOD go_grid->set_toolbar_interactive.
Set focus to the grid. This is not necessary in this
example as there is only one control on the screen
CALL METHOD cl_gui_control=>set_focus EXPORTING control = go_grid.
ENDIF.
ENDMODULE. " STATUS_0100 OUTPUT
*& Module USER_COMMAND_0200 INPUT
MODULE user_command_0200 INPUT.
CASE ok_code.
WHEN 'EXIT200'.
LEAVE TO SCREEN 100.
WHEN'SAVE'.
PERFORM save_changes.
ENDCASE.
ENDMODULE. " USER_COMMAND_0200 INPUT
*& Form get_data
FORM get_data.
Read data from table SFLIGHT
SELECT *
FROM zsflight
INTO TABLE gi_sflight.
ENDFORM. " load_data_into_grid
*& Form change_flight
Reads the contents of the selected row in the grid, ans transfers
the data to screen 200, where it can be changed and saved.
FORM change_flight.
DATA:l_lines TYPE i.
REFRESH gi_index_rows.
CLEAR g_selected_row.
Read index of selected rows
CALL METHOD go_grid->get_selected_rows
IMPORTING
et_index_rows = gi_index_rows.
Check if any row are selected at all. If not
table gi_index_rows will be empty
DESCRIBE TABLE gi_index_rows LINES l_lines.
IF l_lines = 0.
CALL FUNCTION 'POPUP_TO_DISPLAY_TEXT'
EXPORTING
textline1 = 'You must choose a line'.
EXIT.
ENDIF.
Read indexes of selected rows. In this example only one
row can be selected as we are using gs_layout-sel_mode = 'B',
so it is only ncessary to read the first entry in
table gi_index_rows
LOOP AT gi_index_rows INTO g_selected_row.
IF sy-tabix = 1.
READ TABLE gi_sflight INDEX g_selected_row-index INTO g_wa_sflight.
ENDIF.
ENDLOOP.
Transfer data from the selected row to screenm 200 and show
screen 200
CLEAR g_screen200.
MOVE-CORRESPONDING g_wa_sflight TO g_screen200.
LEAVE TO SCREEN '200'.
ENDFORM. " change_flight
*& Form save_changes
Changes made in screen 200 are written to the datbase table
zsflight, and to the grid table gi_sflight, and the grid is
updated with method refresh_table_display to display the changes
FORM save_changes.
DATA: l_traffic_light TYPE c.
Update traffic light field
Update database table
MODIFY zsflight FROM g_screen200.
Update grid table , traffic light field and color field.
Note that it is necessary to use structure g_wa_sflight
for the update, as the screen structure does not have a
traffic light field
MOVE-CORRESPONDING g_screen200 TO g_wa_sflight.
IF g_wa_sflight-paymentsum < 100000.
g_wa_sflight-traffic_light = '1'.
C = Color, 6=Color 1=Intesified on, 0: Inverse display off
g_wa_sflight-line_color = 'C610'.
ELSEIF g_wa_sflight-paymentsum => 100000 AND
g_wa_sflight-paymentsum < 1000000.
g_wa_sflight-traffic_light = '2'.
clear g_wa_sflight-line_color.
ELSE.
g_wa_sflight-traffic_light = '3'.
clear g_wa_sflight-line_color.
ENDIF.
MODIFY gi_sflight INDEX g_selected_row-index FROM g_wa_sflight.
Refresh grid
CALL METHOD go_grid->refresh_table_display.
CALL METHOD cl_gui_cfw=>flush.
LEAVE TO SCREEN '100'.
ENDFORM. " save_changes
chk this blog
/people/vijaybabu.dudla/blog/2006/07/21/topofpage-in-alv-using-clguialvgrid
with regards,
Hema.
pls give points if helpful. -
Passing several fields to various classes and methods?
Passing several fields to various classes and methods?
Hi there.
I have an application that allows a user to define a configuration and save it.
The user can edit an existing configuration, add a new one, or delete an existing one.
Once a configuration is selected the user then starts an application that relies on the selected configuration data. Each configuration holds around 60 fields.
The configuration information is mixed between integers and strings. Around 25 are hidden from the user, and 35 can be modified by the user. The number of fields is not a fixed amount. For example the configuration contains an email-to list and the list for one configuration can have 1 address, and for another could have 10 addresses.
I have decided to redesign using the Model View Controller concept. I am creating the model to hold the configuration information. I am trying to decide if I should have single get and set methods for each field or if I should create some kind of Object that holds all of one configuration and pass this back.
The configuration that is selected does not really require the fields to be sorted in any particular order.
What would you suggest is a good structure to use to pass the configuration information around?
I have been using the Properties class with an .ini file that can be read and updated.
Is this efficient? Doesn�t this impact the speed of processing if I have to read a file every time I want to determine what a particular configuration field is?
Could I just create a class that reads the profile, stores the configuration information for one specific selected config, and then passes the class back to the calling procedure. This would consolidate all the file reading into one class and after that it is held in memory.
Would it be better to read the configuration information into a collection of some sort , or a vector and pass this back to calling routine?
public class MyModel {
//read information to load the field of
Private MyConfig selectedConfiguration = new MyConfig;
Private int selectedField1 = 0;
/** Constructor */
MyModel() {
// open profile, read profile fields the
selectedConfiguration.field1 = profileField1; //assume this is 5
selectedConfiguration.field2 = profileField2; //assume this is 10
selectedConfiguration.field3 = �Test�;
field4ArrayOfStrings = new String[selectedConfiguration.field1 ]
[selectedConfiguration.field2];
selectedConfiguration.field3ArrayOfStrings [0][0] = �First String�
public class MyConfig(){
int field1;
int field2;
String field3;
String[][] field4ArrayOfStrings;
// more stuff here �.
// selectedConfiguration
public void setConfiguration(MyConfig p_config) {
String selectedConfiguration = p_config;
public String getConfiguration() {
return selectedConfiguration;
//The other option is to have get and set for each field
public void setField1(int field1) {
String selectedField1 = field1;
public String getField1() {
return selectedField1;
}Slight correction: reference to field3ArrayOfStrings changed to field4ArrayOfStrings.
Message was edited by:
tkmanjohndjr wrote:
I think the term you want is "cross reference".
Back in the olden days of green bar paper listings and linker maps they used to be quite common. At least they were where I worked.
I have not seen any cross references in some time.
java.lang.Object grr_argh_why_I_oughta_you_dirty_rat; // a pretty cross reference -
Pls help me on finding info abt classes and methods....
hi.. I'm new to java .. but i know the very basics of it.. so that i could write a couple of simple programs.. I've been working wit .NET all these days and MSDN library helps me a gr8 deal.. it gives explanation for every class and methods of the class, even explaining the parameters passed into the methods.. I'm currently workin wit J2ME for developing MIDlets... As i know the basics programming isnt very bad.. but where can i find the explanation for the classes used in micro edition or the methods that belong to the classes...
Is there any facility like MSDN library for java where i can find the whole information...?????
Pls help with....
Thanks for ur patience...* Goto [http://java.sun.com/j2me/docs/|http://java.sun.com/j2me/docs/]
* Click on link "MIDP 2.0 Specification (JSR 118)"
* Under Specification, Click on Download
* Hit Accept License Agreement
* Download ZIP file (not the pdf version)
* Unzip file and view files
* Enter folder "midpng-javadoc-final"
* Open Overview.html
* Find link "JavaDoc API Documentation".
[Ref.|http://www.java-tips.org/java-me-tips/midp/where-is-j2me-api-javadoc.html] -
When should I use abstract classes and when should I use interfaces?
Can any body tell me in which scenario we use /we go for Interface and which scenario we go for abstract class, because as per my knowledge what ever thing we can do by using Interface that thing can also done through abstract class i mean to say that the
behavior of the two class.
And other thing i also want to know that which concept comes first into the programming abstract class or Interface.
S.K NayakThe main differences between an abstract class and an interface:
Abstract
An abstract class can contain actual working code (default functionality), and can have either virtual or abstract method.
An abstract class must be sub-classed and only the sub-classes can be instantiated. Abstract methods must be implemented in the sub-class. Virtual methods may be overridden in the sub-class (although virtual methods typically contain code, you still may
need/want to override them). A good use for an abstract class is if you want to implement the majority of the functionality that a class will need, but individual sub-classes may need slightly different additional functioality.
Interface
An interface only contains the method signatures (method name and parameters), there is no code and it is not a class.
An interface must be implemented by a class. An interface is not a class and so it cannot be sub-classed. It can only be implemented by a class. When a class implements an interface, it must have code in it for each method in the interface's definition.
I have a blog post about interfaces:
http://geek-goddess-bonnie.blogspot.com/2010/06/program-to-interface.html
(sorry, I have no blog posts specific to abstract classes)
~~Bonnie DeWitt [C# MVP]
http://geek-goddess-bonnie.blogspot.com
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