Java programming standard for conditional statement

Hi,
Is it proper Java standard to use constants first in a conditional statement? I've never seen coding in this way, even when I was in college I never saw it in any of our books.
example:
String x = null;
if (null==x){
//Do some stuff
}

kevjava wrote:
yawmark wrote:
...hence, more work.Not if "NAME_KEY" (i.e., the literal value) changes.
~If some wise guy resets it to null, then you've lost all benefit of making a constant out of it to begin withIf that happens, you've got some people problems to deal with! Anyways, if it's really a constant, it'll be final, right?
.... and I was sort-of reiterating that it was a self-named constant... you're right, of course, but I guess I'm just peaved at having to see stuff like...
private String JAN="JAN";
private String FEB="FEB";
// ...and on and on...
// later...
if (FEB.equals(month)) {
// do stuff
} else {
// do stuff
}Have you ever actually seen code like that in production? I wonder, what are you up to that a class needs its own, private, set of months?
My point is that the three-letter abbreviation is always going to be "FEB" (yes, i18N and language specializations aside)Why put them aside, though? They're not exactly corner cases

Similar Messages

Java programming guide for Sun ONE

Where can I find the "Sun ONE LDAP SDK for Java Programming Guide" for version 5.2. ?
I have the programming guide for Netscape Directory SDK 4.0 for Java. Will that do?
Thanks for your help.
[email protected]

this to also create and manage the LDAP groups. We
are using the Sun ONE 5.2 LDAP directory server. Are
there significant advantages to using JNDI over the
SunONE directory SDK, or vice versa?JNDI (bundled with J2SE) in combination with the Booster Pack release version 1.0, provides API support for accessing both static and dynamic Groups. It also provides API support for the new extensions and controls that are made available in Sun ONE DS 5.2.
The Booster Pack can be downloaded from:
http://java.sun.com/products/jndi/
You can also check the LDAP trail of the JNDI Tutorial that contains detailed descriptions and examples of how to use JNDI . It is available at:
http://java.sun.com/products/jndi/tutorial/ldap/index.html

ABAP programming standards for SELECT...ORDER BY....

I recently saw a set of programming standards that stated it was better not to use an ORDER BY clause on a SELECT statement. Instead SELECT into an internal table and use SORT. The actual statement was....."In most cases it is preferable to do the sorting within the ABAP program instead of on the database server. That means: fill the internal table via a SELECT statement and then sort via the SORT statement instead of coding a SELECT u2026 ORDER BY. The sorting of large amounts of data on the database server affects the performance of all users on the system, whereas the sorting within the ABAP program u2018onlyu2019 affects the application server. However, if an index exists on the table that can be used for the sorting then the SELECT u2026 ORDER BY doesnu2019t cause any undue strains on the system."
I think this is no longer correct particularily with regards to Systemi/iSeries which we normally run in 2 tier mode.
What are people opinion on this?

Peter,
the correct answer for DB2 on IBM i is "it depends". To implement "ORDER BY", the optimizer has basically these choices:
- If an index with the columns of the "ORDER BY" clause exists, the database can access the data through this index, which returns them in the desired order. However, the data needs to be fetched row by row, so for each returned row you need one I/O request.
- If such an index does not exist, the database can choose to perform a sequential read into a temporary storage and sort the temporary result set before returning the data to the caller. This is basically the same as reading the data into an internal table and let ABAP do the sort. Even if an index exist, reading the whole table into memory and sorting it there may be faster, because on a sequential read, the database can execute a "blocked" fetch rather than many individual I/O operations. You may see this if the table is relatively small.
- If such an index does not exist, the database could also choose to create a temporary index and access the data through the temporary index. For the first execution, you don't gain much, but subsequent executions may perform much better. However, after an IPL you loose all temporary indexes, so the index needs to be built again on the first execution after the IPL.
If you code your ABAP to read the table sequentially and sort it in memory, you are forcing the second implementation. If you code ABAP with the ORDER BY in the SELECT statement, you allow the database optimizer to choose the best possible implementation depending on the size of the table, the size of the result set, and the available indexes.
If your table is relatively large but the result set (based on the WHERE clause) is relatively small, make sure to have an index that combines the WHERE clause elements returning only one value with the ORDER BY clause elements.
For example, if you have a query like:
SELECT * FROM T
WHERE A = ? AND B = ? AND C IN (?, ?, ?)
ORDER BY D, E
you should have an index over columns A, B, D, and E for the best possible performance. A and B in the index can be used to limit the result set without any influence on the sort order D, E, but C cannot.
Kind regards,
Christian Bartels.

How to abend the java program -if the condition fails

Hi
My program counts the number of headers in the input file and if the condition fails to satisfy the number we expected , it should comeout of the java program . Is their a specific statement to abend the program in java .
if(columnCount == 5)
// do all the steps
else
//abend the program }
how to do that .... is it System.exit(1) or anything else
thanks..
Edited by: 1sai on Apr 23, 2009 6:52 PM

BigDaddyLoveHandles wrote:
It must have been that the [card sorters|http://en.wikipedia.org/wiki/Card_sorter] were making such a ruckus that I didn't hear it. The model 84 -- 2,000 cards a minute? -- dämn, that's sweet.
I remember the first time I saw a card sorter in action, thinking it was kind of cool.
I also think the teacher used it to describe some sorting algorithm, maybe radix sort??
You've got me thinking, that might be part of the problem with computing today, not enough moving parts. No big tape drives spinning and oscillating. And few if any line printers anymore. Now there's an interesting piece of equipment.

Accessing oracle DB from a java program - question for oracle driver

Hi,
I have Oracle 10 G under vista on my desktop. I am trying to write a simple java program to access/update database tables. I saw in one of oracle example to import 2 packages - namely --- import oracle.jdbc.driver.*; import oracle.sql.*;
Where do I find these 2 packages. Also I read some documentation to download drivers. I would like to use 2 drivers, the thin driver and the OCI driver. Can someone tell me where I can find these drivers and where do I copy these two drivers - so javac and java command can recognize it.
I will greatly appreciate the help. Julia
My program is as follows
(It was working few years ago but things have changed now and I have Vista because my old machine died):
import java.sql.*; // JDBC package
//import com.inet.tds.JDBCRowSet;
import java.util.*;
import oracle.jdbc.driver.*;
import oracle.sql.*;
public class HomeDB
run as follows:
C:\Documents and Settings\MMM>cd \jj
C:\john>set CLASSPATH=.;c:\oracle9i\classes12;%CLASSPATH%
C:\john>javac HomeDB.java
C:\john>java HomeDB
King: 24000.0
Kochhar: 17000.0
De Haan: 17000.0
Hunold: 9000.0
Ernst: 6000.0
Austin: 4800.0
public static void main(String[] argv)throws SQLException
Connection conn=null;
try // may throw a SQLException
conn = getConnection();
doQuery (conn);
catch (SQLException e)
System.err.println(e.getErrorCode() + ": " + e.getMessage());
finally // make sure the connection is closed
if (conn != null) try {conn.close();} catch (SQLException e) {};
//out.close(); // close PrintWriter stream
private static Connection getConnection() throws SQLException
String username = "scott";
String password = "tiger";
String url = "jdbc:oracle:thin:@localhost:1521:newora";
// "jdbc:oracle:thin:@localhost:1521:COCKYJOB";
Connection conn = null;
String driver = "oracle.jdbc.driver.OracleDriver";
try {
Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
} catch ( ClassNotFoundException cnfex ) {
System.err.println(
"Failed to load JDBC/ODBC driver." );
cnfex.printStackTrace();
}catch (Exception e){
e.printStackTrace();
//DriverManager.registerDriver(new oracle.jdbc.OracleDriver());
conn = java.sql.DriverManager.getConnection(url,username,password);
conn.setAutoCommit(false);
return conn;
private static void doQuery (Connection c) throws SQLException
// statement to be executed
String query = "SELECT ename, job, mgr FROM EMP";
Statement st = null;
ResultSet rs = null;
try // make sure the close statements are executed (in the finally block)
// create the statement
st = c.createStatement();
// execute the query
rs = st.executeQuery(query);
// process results
while (rs.next())
// get the employee last name
String eName = rs.getString("ename");
String eJob = rs.getString("job");
String eMgr = rs.getString("mgr");
System.out.println("Emp Name:" + eName +
"Job: " + eJob +
"MGR: " + eMgr);
finally // make sure the close statements are executed
// close the result set if it exists
if (rs != null) try {rs.close();} catch (Exception e) {};
// close the statement if it exists
if (st != null) try {st.close();} catch (Exception e) {};
Edited by: user455788 on Dec 19, 2008 9:13 PM

You can download the drivers from http://www.oracle.com/technology/software/tech/java/sqlj_jdbc/index.html.
Note that oracle.jdbc.driver is desupported after 10.2, http://forums.oracle.com/forums/ann.jspa?annID=201, so you might want to consider using a DataSource to provide Connections.
E.G.
{message:id=2819114}

XSL vs CFML for conditional statements

I want to use a server side transformation of an XML document
using XSL to produce a set of HTML, Doc and PDF documents. However,
I need to do some conditional processing (mainly if then formating
issues for cases of null data) and I am wondering if I am better
off doing them in XSL or in CFML. Does any one know of performance
issues versus one way or another or can point me to some
literature?

The XSQL Pages framework has never had an <xsql:if> conditional as a built-in action, so the article must be in error.Actually, the article (written by members of the Oracle XML Product Development Team) refers to the use of "<xsl:if>" within XSQL pages, not "<xsql:if>". Here's the excerpt from the article at the site http://www.oracle.com/oramag/oracle/01-jan/index.html?o11xml.html -
Support for XSLT Tags in XSQL
Oracle XSQL pages are templates that enable you to assemble dynamic XML datapages based on one or more parameterized SQL queries. The processor then uses XSLT to transform the datapage to produce a final result in any desired XML, HTML, or text-based format. However, you can also use XSLT to assemble the XML datapages. For example, you can use XSLT to execute SQL queries conditionally by using <xsl:choose> or <xsl:if>. The following XSQL page shows the use of xsl:if to retrieve a summary or detailed information on the book list:
<?xml version="1.0"?>
<xsql:query connection="demo" xmlns:xsql="urn:oracle-xsql"
xmlns:xsl="http://www.w3.org/1999/XSL /Transform">
<xsl:if test="$detail = 'yes'">
SELECT * FROM scott.BookList
</xsl:if>
<xsl:if test="$detail = 'no'">
SELECT Title, Authorname FROM scott.BookList</xsql:query>
</xsl:if>
</xsql:query>
I'm just looking for clarification whether this is in fact true.
Thanks,
Michael
The Online XSQL Documentation features examples illustrating how to accomplish this functionality. See the doc there, and search for "XSQL Servlet Conditional Statements".

Java Programming Exercises for Begginers?

I am doing some self study on JAVA and looking for some programming exercises. If anyone could give me resources it would be a lot of help. thanks
Message was edited by:
the_atom

Both these links are pretty good.
http://www.freejavaguide.com/corejava.htm
http://www.java.sun.com/docs/books/tutorial/

How do I exit a java program based on condition can i use system.exit

I have java program that is called by another program that I dont have control on. My program returns a bigdecimal... but if the ordernumber is empty in my program i dont wnat to do anything.. does system.exit work in that condition... i put it int he else if ordernumber is empty condition.. but i dont think that is the right approach..

When software module is expected to bring some result, it should bring the result, positive or negative. I think you should check what your counterpart software expects as positive or negative result. And then implement your software this way. You can use System.exit, but this call is employed usually to indicate status with the software after it's completion and not to return any resulting value.
http://java.sun.com/j2se/1.4.2/docs/api/java/lang/System.html#exit(int)

Java Programming Resources for starting out

Hey guys,
What are the best resources for starting out with Java. I did a bit of work with Java in my Uni course but it was about 2 years ago. I'd like to go over it from the start and get familar with everything again.
Can anyone suggest some good places to get Resources, Tutorials and Exercises for Java Programming?
Thanks in advance.

Getting Started With Java
[Sun's basic Java tutorial|http://java.sun.com/docs/books/tutorial/]
[Sun's New To Java Center|http://java.sun.com/learning/new2java/index.html]
Includes an overview of what Java is, instructions for setting up Java, an intro to programming (that includes links to the above tutorial or to parts of it), quizzes, a list of resources, and info on certification and courses.
jGuru
A general Java resource site. Includes FAQs, forums, courses, more.
[Yawmarks List|http://forums.devshed.com/java-help-9/resources-for-learning-java-249225.html]
[The Java Developers Almanac|http://www.amazon.com/exec/obidos/tg/detail/-/0201752808?v=glance]
[http://javaalmanac.com|http://javaalmanac.com]
Bruce Eckel's [Thinking in Java(Available online.)|http://mindview.net/Books/DownloadSites]
Joshua Bloch's [Effective Java|http://www.amazon.co.uk/exec/obidos/Author=Bloch,%20Josh]
Bert Bates and Kathy Sierra's [Head First Java|http://www.amazon.com/exec/obidos/tg/detail/-/0596004656?v=glance ]
James Gosling's [The Java Programming Language|http://www.bookpool.com/sm/0321349806]
Gosling is the creator of Java. It doesn't get much more authoritative than this.
Joshua Bloch and Neal Gafter [Java Puzzlers.|http://www.javapuzzlers.com/]

Desktop java program: wait for page to load

We're using a macro-builder which records actions and re-executes them via a java program. Basically, the program is supposed to open IE, go to a page, enter a username and password, and click a link within the new page that comes up after login. The issue at hand is that the second page takes too long to load, and the recorded "click" in the macro occurs to soon. Is there any way to identify when the page has completed loading before the app continues?
Thanks,
Jonathan

Is there any way to identify when the page has
completed loading before the app continues?Not in Java. Probably not even in Visual Basic (I wrote some VB programs that attempted to do that sort of thing several years ago and they never worked properly).

Recursive Java programming method for executing recursive SQL queries

Anybody has a Java/JDBC example method to execute recursive SQL queries and print results? The method has to work for any number of queries and levels and the first query passes the parameter to the second query.
Edited by: user4316962 on Jun 12, 2011 1:59 PM

user4316962 wrote:
Guys, the problem what I am trying to solve is much more complex and I don’t think SQL level recursion is enough. I am looking for Java solution with SQL queries in it to make it more flexible and DB independent.
If you want to do recursion in SQL then it has nothing to do with Java.
And if you want to do recursion in Java then the idiom itself has nothing to do with SQL.
Other than that you have provided enough detail for anyone to even guess at what you are asking.
As a start I am not even sure that you understand what recursion is nor how JDBC works. (But it could be that you are using the terms to mean something else.)
And looking at your original post it could be nothing more than that you are looking for a design pattern - perhaps the interpreter.

Installer for a Java Program

Hello, folks.
I've written an application that I feel is ready to show to others, and would like to provide it with an installer.
I need to check that JRE 1.4 is installed, install it if it isn't, install the application to a directory, set install/uninstall options in the control panel, and add a start menu item. (This will be a Windows-platform installer.)
Could any of you suggest a free (not demo) installer system that I could use? I've heard that there are some good ones out there, but I don't have their names and associated URL's.
thanks,
Andrew

Hello All,
This is may be bit of a tangent, but hopefully it can be helpful regardless...
I'm looking into installer programs that are java friendly with the ability to generate a gui-based install program for multiple platforms. I went out and tried to find as many programs that match these specs (list below). Before I dive headlong into demo-sampling-mode - I was hoping folks would share any positive or negative experiences they've had with any of the apps listed below.
http://www.denova.com/ - DeNova
http://www.fawcette.com/Archives/premier/mgznarch/javapro/2000/06jun00/rv0006/rv30006.asp - InstallShield Java Edition 3.0
http://www.alphaworks.ibm.com/tech/beanbag - BeanBag
http://www.alphaworks.ibm.com/tech/installtoolkit - Install Toolkit for Java
http://www.jadcentral.com/codecentral/code_profile.jsp?category_ID=4&code_ID=112 - ITW Installer For Java Applications
http://www.zerog.com/ - InstallAnywhere (some free, some not)
http://www.gjt.org/info/design/autorad.shtml - AutoRad [GPL]
http://www.xenonsoft.demon.co.uk/products/freeinstaller/index.html - freeinstaller [Open Source]
http://www.izforge.com/izpack/ - IzPack [Open Source]
http://www.toolshed.com/download/installer/install.html - Java Self Installer [GPL]
http://liftoff.sourceforge.net/ - Lift-Off [GPL]
http://packlet.sourceforge.net/ - Packlet installer tool [Open Source, LGPL]
http://vainstall.sourceforge.net/ - VAInstall [GPL]
Comparisons:
http://www.zerog.com/products_pu_05.html
Cheers,
Enrique
cc comp.lang.java.softwaretools
cc forum.java.sun.com > Java Programming > Installer for a Java Program

New Java Programming Student Needs Help

Hey everyone,
I've just started taking a Java programming class at Penn State University, and I have had some prior experience with programming, i.e. C, C++, HTML, SQL. However, this will be my first attempt at Java. I know there are a lot of similarities between C++ and Java, but I'm still a little lost on some methodology.
To get myself going, I've been looking through the textbook a little and came across a problem that gave me some difficulty. I'll write out the outline:
A company pays its employees as managers (who receive a fixed weekly salary), hourly workers (who receive a fixed hourly wage for up to the first 40 hours they work and time and a half (i.e. 1.5 times their hourly wage) for overtime hours worked, commission workers (who receive $250 plus 5.7% of their gross weekly sales), and pieceworkers (who receive a fixed amount of money per item for each of the items they produce � each pieceworker in this company works on only one type of item).
+Define a Java class named EmployeePayment that includes functionality to compute the weekly pay for each employee. You do not know the number of employees in advance. Each type of employee has its own pay code: Managers have paycode 1, hourly workers have paycode 2, commission workers have paycode 3 and pieceworkers have paycode 4.+
+Define a main method that creates an instance of the EmployeePayment class, and calls the setManagerPay method to set the managers weekly salary to $625.00. The main method should then prompt the user for the paycode ��Enter paycode (-1 to end): �, validate the input and perform the associated processing for that paycode. Your program should allow the user to process employees until a paycode of -1 has been entered. Use a switch structure to compute each employee�s pay, based on the employee�s paycode. Within the switch, prompt the user (i.e. the payroll clerk) to enter the appropriate facts your program needs to calculate each employee�s pay based on that employee�s paycode, invoke the respective method (defined below) to perform the calculations and return the weekly pay for each type of employee, and print the returned weekly pay for each employee.+
+Define a setManagerPay method that accepts and stores the fixed weekly salary value for managers.+
+A private instance variable weeklyManagerPay should be defined in the EmployeePayment class to support these accessor and mutator methods.+
+Define a calcManagerPay method that has no parameters and returns the fixed weekly salary.+
+Define a calcHourlyWorkerPay method that accepts the hourly salary and total hours worked as input parameters and returns the weekly pay based on the hourly worker pay code description.+
+Define a calcCommWorkerPay method that accepts the gross weekly sales as an input parameter and returns the weekly pay based on the commission worker pay code description.+
+Define a calcPieceWorkerPay method that accepts the number of pieces and wage per piece as input parameters and returns the weekly pay based on the piece worker pay code description.+
+Once all workers have been processed, the total number of each type of employee processed should be printed. Define and manage the following private instance variables (*numManager*, numHourlyWorker, numCommWorker, and numPieceWorker) within the EmployeePayment class. What are the ways in which these variables can be updated?+
Sorry for the length, but I wanted this to be thorough. Basically, I'm having the most trouble writing the switch statement, and outputting the total number of each type of employee...
Any help and pointers will be greatly appreciated...thanks all.

You said you've written C and C++ code before. I don't have an excellent memory but from the little code that I wrote in C, I believe the switch statement is exactly the same.
Read this: [http://java.sun.com/docs/books/tutorial/java/nutsandbolts/switch.html]
If you're having trouble understanding something post what your specific problem is. No one is going to write your homework for you, but many, myself included, would be more than willing to help if you're really stumped. Just post your concise problem.
Edited by: sheky on Mar 12, 2008 9:52 PM

Possible? output a string from a java program into a running program

I'm not sure if it is plausible, but this is my dilemma. My java program searches for street names in a specific region, then outputs the nearest street. I would like to synch this up with Google Earth, and output the street name into it, so it would go ahead and be able to search it right away. Is this possible, or should I attempt some other route?

Check out my runCmd method. It gives an example of running another program and listening for the output. I built this to run javac and show the output in my custom editor.
You'll see some classes in here that are not standard java classes, in particular InfoFetcher. Don't worry, this is just a utility I wrote for convenient handling of inputstreams. You can handle the inputstreams without it, but if you really want it, it's probably posted somewhere in these forums.
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             try {
                  System.out.println("cmd: " + cmd);
                  Process p = Runtime.getRuntime().exec(cmd);
                  InputStream stream = p.getInputStream();
                  InputStream stream2 = p.getErrorStream();
                  InfoFetcher info = new InfoFetcher(stream, new byte[512], 500);
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                       int currentLength = 0;
                       public void gotAll(InputStreamEvent ev) {}
                       public void gotMore(InputStreamEvent ev) {
                            String str = new String(ev.buffer, currentLength, ev.getBytesRetrieved());
                            currentLength = ev.getBytesRetrieved();
                            System.out.print(str);
                  info.addInputStreamListener(l);
                  Thread t = new Thread(info);
                  t.start();
                    InfoFetcher info2 = new InfoFetcher(stream2, new byte[512], 500);
                  InputStreamListener l2 = new InputStreamListener() {
                       int currentLength = 0;
                       public void gotAll(InputStreamEvent ev) {}
                       public void gotMore(InputStreamEvent ev) {
                            String str = new String(ev.buffer, currentLength, ev.getBytesRetrieved());
                            currentLength = ev.getBytesRetrieved();
                            System.out.print("(Error) " + str);
                  info2.addInputStreamListener(l2);
                  Thread t2 = new Thread(info2);
                  t2.start();
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How to run java programs from a master java program?

Hello,
I have several java programs which run from the command prompt. I am seeking help with code for starting java programs from within a java program. For example, a program called master.java works something like this:
import java.*;
create connection pool
create variables and result sets
start/run slave1.java (var1, var2);
start/run slave2.java (var3, var4, var5);
start/run slave3.java (var1, var4);
end of program master.java
Each of the slave.java programs will run for up to an hour. I do not want the master.java program to pause for each slave program to stop. Instead, the master program will keep running and multiple slave programs will be running simultaneously with the master program. When a slave program starts, it is on its own. Also, if possible, I would like to have each of these slave.java programs open in a new separate command window, so I can observe each slave program running in separate windows.
Any suggestions for code or helpful documentation are greatly appreciated.
Thank you,
Logan

Thank you all.
At the bottom of master.java I have successfully started a batch file with these lines:
String jcmd = "cmd.exe /c start c:/data/simulations/MsgViewCount2.bat";
Process proc = Runtime.getRuntime().exec(jcmd);
But I still cannot get a java program to start. Here is one variation I have tried:
String [] cmdArray = new String[2];
cmdArray[0] = "java";
cmdArray[1] = "slave1";
Runtime runtime = Runtime.getRuntime();
Process process = runtime.exec(cmdArray);
This compiles, and no errors occur, but nothing happens.
Regarding this comment:
Why Runtime.exec? Either make the slaves Runnable or
just call their main() methods.
Oh, I see. Sepearate output. :PNone of the slave.java programs have any output.
Thanks again.

Java programming standard for conditional statement

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