Java?!?! Where to start, where to go!

I'm just starting to look into Java and to be honest, there's so much information that it's confusing! I've no idea where to even begin to get a foothold so I thought I would post, tell you a little about me, and maybe you can help point me in the right direction. Knowing nothing about Java I'm simply overwhelmed looking at a website and seeing Java, Jdk, JE, EE, ME, JDK, Netbeans, Eclipse, FX, Wombats, BlueJ, Applet Ajax, IDE, ... ARGH!!
So.... here's who I am and what I'm after....
I've done development work in the past using whatever languages were needed at the time. Perl, PhP, Visual Basic, Visual Studio, etc. etc. I was out of it for quite a while and now, at 39, am looking at getting back into development work fulltime. After doing a lot of research, I understand that Java is one of the best languages to have under your belt nowadays. Java is one of the languages I know nothing about or where to even begin. I've got some people telling me to download different IDE's and do tutorials through interfaces, and other people telling me to just download the JDK and use notepad while learning. I opted for the 'notepad' method for now and have constructed the gratuitous helloworld programs and all that with no problems... My normal development jobs, including my current one, are just developing simple applications for end users. Issue tracking programs, records management programs, inventory programs, simple database interfaces for data mining... nothing special.
What I'm trying to work out is this. What exactly do I need to learn to become a standard Java developer, where should I start? I do have a lot of catching up to do with technology but I am familiar with development, I just need a lot of study time. Seeing all the different options and software and packages, I'm at a loss. If I'm right, from what I've been able to work out so far, is that I want to shoot for the Entry Level SCJA cert and work all the way up to the SCJD cert and then figure out where to go after that.
What are the best things, or most common things, to learn right off the bat to get out in the java workforce as quickly as possible. There must be some common place to start and there are just so many acronyms and packages and things for java that it seems a bit impossible to know where to start! I don't want to, for instance, learn java using nothing more than notepad and the JDK only to get a job and find out they use some sort of Java IDE or something like that.
I appreciate any help and websites you guys can give me. Thanks!

No better place to start than here: [New to Java Center|http://java.sun.com/learning/new2java/index.html]
~

Similar Messages

Java 7 Web start fails to download Java 1.6 version

Sorry for the almost exact duplication of a previous thread, but that was closed (Java 7 Web start fails to download Java 1.6 version
When launching an application requiring Java 1.6 with a Java 1.7 web start it fails when it tries to download 1.6 with the following message:
"Unable to download http://javadl-esd.sun.com/update/1.6.0/1.6.0_29-b11.xml for installation"
Problem only seems to occur on Windows 7 (64 bit), seems fine on Windows XP.
Bug has been raised with Oracle by poster Matt Taylor - http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7168311
Does anybody have any ideas?
Thanks,
Lee.

igor wrote:
Could you please collect and provide more info.
In particular:
0) Explain how exactly you launch JNLP when it does not work.We have a website with a link to a jnlp file. User clicks on the link the jnlp file downloads and installs.
"install the jnlp from the dos window" - do you mean run "javaws applicationURL"?Yes. But actually that only worked because we had already installed a Java 6 version.
When it does not work do you use Deployment Toolkit to embed link into web page?
1) screenshot of the errorHere are links to several screenshots of errors we get:
http://dl.waterford.org/pics/error_install.png
http://dl.waterford.org/pics/error2.png
http://dl.waterford.org/pics/error3.png
Here is a link to the error in the java webstart failure dialog (details):
http://dl.waterford.org/pics/errormsg.txt
2) Enable full trace details (see http://docs.oracle.com/javase/7/docs/webnotes/tsg/TSG-Desktop/html/plugin.html#gcexdf)
and post trace fileHere is a link to the java console with full trace details:
http://dl.waterford.org/pics/javaconsole.txt
3) Install WireShark and see what http requests are made. Please post all request/response pairshttp://dl.waterford.org/pics/packets.pcap
Edited by: 933472 on May 10, 2012 1:30 PM

BI JAVA is not started.

Hi All,
java is not started in Bi system, We restarted the system then ABAP comes up but JAVA is not workiong
Dispatcher is running server0 is running BUT SDM is not running its in "Stoped"
i checked the logs also but no updates.
Regards
Babu

Hello Babu,
Dispatcher is running server0 is running BUT SDM is not running its in "Stoped"
Its gr8 that Dispatcher & Server nodes are running. So your Java engine is running as of now however only SDM is down.
Now, did you tried to restart SDM process manually with JCMON tool(jcmon pf=<instance profile of the Java central instance>) ?? Did it got started and then stopped again ? Please check SDM logs(They are located in the /usr/sap/<SID>/<INSTANCE_NAME>/SDM/program/log directory) for details.. why its going down.
Also SDM gets stopped if someone try to lodin with SDM user and wrong passwords.. do u have this problem ?
This can be helpful for you as well :
http://help.sap.com/saphelp_nw04/helpdata/en/76/fb72ec091f4bf8a2d8ba321bb7e8d9/content.htm
thanks
ashish

Exception in thread "Main Thread" java.lang.NoClassDefFoundError: start

Hi
I am Migrating my app from weblogic 8.1 to 10.3 . I am trying to run the startWeblogic.sh file its failing with below error .Please suggest me am unable to resolve
CLASSPATH=:/opt/bea/patch_wlw1030/profiles/default/sys_manifest_classpath/weblogic_patch.jar:/opt/bea/patch_wls1030/profiles/default/sys_manifest_classpath/weblogic_patch.jar:/opt/bea/patch_cie660/profiles/default/sys_manifest_classpath/weblogic_patch.jar:/opt/bea/jrockit_160_14/lib/tools.jar:/opt/bea/wlserver_10.3/server/lib/weblogic_sp.jar:/opt/bea/wlserver_10.3/server/lib/weblogic.jar:/opt/bea/modules/features/weblogic.server.modules_10.3.0.0.jar:/opt/bea/wlserver_10.3/server/lib/webservices.jar:/opt/bea/modules/org.apache.ant_1.6.5/lib/ant-all.jar:/opt/bea/modules/net.sf.antcontrib_1.0.0.0_1-0b2/lib/ant-contrib.jar::/opt/bea/wlserver_10.3/common/eval/pointbase/lib/pbclient57.jar:/opt/bea/wlserver_10.3/server/lib/xqrl.jar::
PATH=/opt/bea/wlserver_10.3/server/bin:/opt/bea/modules/org.apache.ant_1.6.5/bin:/opt/bea/jrockit_160_14/jre/bin:/opt/bea/jrockit_160_14/bin:/usr/local/bin:/bin:/usr/bin:/home/quoteapp/bin:/prod/qcquoting/bin:/home/quoteapp/bin/apache-ant-1.6.5/bin:/opt/bea/jrockit_160_14/bin
* To start WebLogic Server, use a username and *
* password assigned to an admin-level user. For *
* server administration, use the WebLogic Server *
* console at http://hostname:port/console *
starting weblogic with Java version:
java version "1.6.0_14"
Java(TM) SE Runtime Environment (build 1.6.0_14-b08)
BEA JRockit(R) (build R27.6.5-32_o-121899-1.6.0_14-20091001-2113-linux-x86_64, compiled mode)
Starting WLS with line:
/opt/bea/jrockit_160_14/bin/java -jrockit -Xms256m -Xmx512m -Xverify:none -da -Dplatform.home=/opt/bea/wlserver_10.3 -Dwls.home=/opt/bea/wlserver_10.3/server -Dweblogic.home=/opt/bea/wlserver_10.3/server -Dweblogic.management.discover=true -Dwlw.iterativeDev= -Dwlw.testConsole= -Dwlw.logErrorsToConsole= -Dweblogic.ext.dirs=/opt/bea/patch_wlw1030/profiles/default/sysext_manifest_classpath:/opt/bea/patch_wls1030/profiles/default/sysext_manifest_classpath:/opt/bea/patch_cie660/profiles/default/sysext_manifest_classpath -Dweblogic.Name=quoting -Djava.security.policy=/opt/bea/wlserver_10.3/server/lib/weblogic.policy start weblogic.Server
Exception in thread "Main Thread" java.lang.NoClassDefFoundError: start
Could not find the main class: start. Program will exit.
am attaching my sh file aslo below
!/bin/sh
# WARNING: This file is created by the Configuration Wizard.
# Any changes to this script may be lost when adding extensions to this configuration.
# --- Start Functions ---
stopAll()
     # We separate the stop commands into a function so we are able to use the trap command in Unix (calling a function) to stop these services
     if [ "X${ALREADY_STOPPED}" != "X" ] ; then
          exit
     fi
     # STOP POINTBASE (only if we started it)
     if [ "${POINTBASE_FLAG}" = "true" ] ; then
          echo "Stopping PointBase server..."
          ${WL_HOME}/common/bin/stopPointBase.sh -port=${POINTBASE_PORT} -name=${POINTBASE_DBNAME} >"${DOMAIN_HOME}/pointbaseShutdown.log" 2>&1
          echo "PointBase server stopped."
     fi
     ALREADY_STOPPED="true"
     # Restore IP configuration the node manager starts IP Migration
     if [ "${SERVER_IP}" != "" ] ; then
          ${WL_HOME}/common/bin/wlsifconfig.sh -removeif "${IFNAME}" "${SERVER_IP}"
     fi
# --- End Functions ---
# This script is used to start WebLogic Server for this domain.
# To create your own start script for your domain, you can initialize the
# environment by calling @USERDOMAINHOME/setDomainEnv.
# setDomainEnv initializes or calls commEnv to initialize the following variables:
# BEA_HOME - The BEA home directory of your WebLogic installation.
# JAVA_HOME - Location of the version of Java used to start WebLogic
# Server.
# JAVA_VENDOR - Vendor of the JVM (i.e. BEA, HP, IBM, Sun, etc.)
# PATH - JDK and WebLogic directories are added to system path.
# WEBLOGIC_CLASSPATH
# - Classpath needed to start WebLogic Server.
# PATCH_CLASSPATH - Classpath used for patches
# PATCH_LIBPATH - Library path used for patches
# PATCH_PATH - Path used for patches
# WEBLOGIC_EXTENSION_DIRS - Extension dirs for WebLogic classpath patch
# JAVA_VM - The java arg specifying the VM to run. (i.e.
# - server, -hotspot, etc.)
# USER_MEM_ARGS - The variable to override the standard memory arguments
# passed to java.
# PRODUCTION_MODE - The variable that determines whether Weblogic Server is started in production mode.
# POINTBASE_HOME - Point Base home directory.
# POINTBASE_CLASSPATH
# - Classpath needed to start PointBase.
# Other variables used in this script include:
# SERVER_NAME - Name of the weblogic server.
# JAVA_OPTIONS - Java command-line options for running the server. (These
# will be tagged on to the end of the JAVA_VM and
# MEM_ARGS)
# For additional information, refer to the WebLogic Server Administration
# Console Online Help(http://e-docs.bea.com/wls/docs103/ConsoleHelp/startstop.html).
# Call setDomainEnv here.
DOMAIN_HOME=/prod/qcquoting/int/builds/qoaquoting
. ${DOMAIN_HOME}/bin/setDomainEnv.sh $*
SAVE_JAVA_OPTIONS="${JAVA_OPTIONS}"
SAVE_CLASSPATH="${CLASSPATH}"
# Start PointBase
PB_DEBUG_LEVEL="0"
if [ "${POINTBASE_FLAG}" = "true" ] ; then
     ${WL_HOME}/common/bin/startPointBase.sh -port=${POINTBASE_PORT} -debug=${PB_DEBUG_LEVEL} -console=false -background=true -ini=${DOMAIN_HOME}/pointbase.ini >"${DOMAIN_HOME}/pointbase.log" 2>&1
fi
JAVA_OPTIONS="${SAVE_JAVA_OPTIONS}"
SAVE_JAVA_OPTIONS=""
CLASSPATH="${SAVE_CLASSPATH}"
SAVE_CLASSPATH=""
trap 'stopAll' 1 2 3 15
if [ "${PRODUCTION_MODE}" = "true" ] ; then
     WLS_DISPLAY_MODE="Production"
else
     WLS_DISPLAY_MODE="Development"
fi
if [ "${WLS_USER}" != "" ] ; then
     JAVA_OPTIONS="${JAVA_OPTIONS} -Dweblogic.management.username=${WLS_USER}"
fi
if [ "${WLS_PW}" != "" ] ; then
     JAVA_OPTIONS="${JAVA_OPTIONS} -Dweblogic.management.password=${WLS_PW}"
fi
CLASSPATH="${CLASSPATH}${CLASSPATHSEP}${MEDREC_WEBLOGIC_CLASSPATH}"
CLASSPATH="${CLASSPATH}${CLASSPATHSEP}./config/order_properties/"
echo "."
echo "."
echo "JAVA Memory arguments: ${MEM_ARGS}"
echo "."
echo "WLS Start Mode=${WLS_DISPLAY_MODE}"
echo "."
echo "CLASSPATH=${CLASSPATH}"
echo "."
echo "PATH=${PATH}"
echo "."
echo "***************************************************"
echo "* To start WebLogic Server, use a username and *"
echo "* password assigned to an admin-level user. For *"
echo "* server administration, use the WebLogic Server *"
echo "* console at http://hostname:port/console *"
echo "***************************************************"
# Set up IP Migration related variables.
# Set interface name.
if [ "${Interface}" != "" ] ; then
     IFNAME="${Interface}"
else
     IFNAME=""
fi
# Set IP Mask.
if [ "${NetMask}" != "" ] ; then
     IPMASK="${NetMask}"
else
     IPMASK=""
fi
# Perform IP Migration if SERVER_IP is set by node manager.
if [ "${SERVER_IP}" != "" ] ; then
     ${WL_HOME}/common/bin/wlsifconfig.sh -addif "${IFNAME}" "${SERVER_IP}" "${IPMASK}"
fi
# START WEBLOGIC
echo "starting weblogic with Java version:"
${JAVA_HOME}/bin/java ${JAVA_VM} -version
if [ "${WLS_REDIRECT_LOG}" = "" ] ; then
     echo "Starting WLS with line:"
     echo "${JAVA_HOME}/bin/java ${JAVA_VM} ${MEM_ARGS} ${JAVA_OPTIONS} -Dweblogic.Name=${SERVER_NAME} -Djava.security.policy=${WL_HOME}/server/lib/weblogic.policy ${PROXY_SETTINGS} ${SERVER_CLASS}"
     ${JAVA_HOME}/bin/java ${JAVA_VM} ${MEM_ARGS} ${JAVA_OPTIONS} -Dweblogic.Name=${SERVER_NAME} -Djava.security.policy=${WL_HOME}/server/lib/weblogic.policy ${PROXY_SETTINGS} ${SERVER_CLASS}
else
     echo "Redirecting output from WLS window to ${WLS_REDIRECT_LOG}"
     ${JAVA_HOME}/bin/java ${JAVA_VM} ${MEM_ARGS} ${JAVA_OPTIONS} -Dweblogic.Name=${SERVER_NAME} -Djava.security.policy=${WL_HOME}/server/lib/weblogic.policy ${PROXY_SETTINGS} ${SERVER_CLASS} >"${WLS_REDIRECT_LOG}" 2>&1
fi
stopAll
popd
# Exit this script only if we have been told to exit.
if [ "${doExitFlag}" = "true" ] ; then
     exit
fi

I can not see main class weblogic.jar file in your class path.
Under MW_HOME there is a file by name configure.cmd/sh, run it to set acl and class path. Then try to start weblogic server. U can edit the startWeblogic.sh/cmd so that every time it will execute after calling configure.sh/cmd file.

AS Java applications not starting after patching from 2004s SPS10 to SPS11

Hi folks,
after patching our NetWeaver 2004s from SPS10 to SPS11 and the Kernel from 7.00.83.0 to 7.00.95.0, the applications on the AS Java do not start up automatically any more.
Under the following URLs, the same error is shown:
http://<fully qualified host name>:51000/
http://<fully qualified host name>:51000/nwa
http://<fully qualified host name>:51000/sap/monitoring/SystemInfo
http://<fully qualified host name>:51000/useradmin/
http://<fully qualified host name>:51000/wsnavigator
http://<fully qualified host name>:51000/uddiclient
503 Service Unavailable
SAP J2EE Engine/7.00
Application stopped.
Details: You have requested an application that is currently stopped
http://<fully qualified host name>:51000/webdynpro/welcome/Welcome.jsp
itself works, the two links Content Administrator and Web Dynpro Console both lead to the same 503 error described above
On http://<fully qualified host name>:51000/irj, the error message is different:
com.sap.engine.services.deploy.container.ApplicationInManualStartUpException:
Application sap.com/com.sap.portal.fpn.accessservice cannot be started because is in MANUAL start-up mode..
Exception id: 09:33_09/05/07_0003_102709250
See the details for the exception ID in the log file
In std_server0.out we have the following entries, right after the list of all services that were started:
ServiceManager started for 39904 ms.
Framework started for 46720 ms.
SAP J2EE Engine Version 7.00 PatchLevel is running!
PatchLevel January 31, 2007 18:37 GMT
May 9, 2007 9:40:19 AM com.sap.portal.prt.sapj2ee.error [SAPEngine_Application_Thread[impl:3]_3] Fatal:
The last line with com.sap.portal.prt.sapj2ee.error is listed another 131 times, and there is also the following message:
### Excluding compile: com.sapportals.portal.prt.jndisupport.util.AbstractHierarchicalContext::lookup
We can connect to the system using Visual Administrator. Under Server->Services->Deploy, most applications are not running. It is possible to start a few applications manually, others however do not start showing different exceptions.
We have AS ABAP and AS Java installed, as well as BI, DI, EP and EPC. AS ABAP seems to be running fine.
We have also noticed the following deviations in JSPM:
BC_FES_IGS is Release 7.00 SP Level 7.0
EP_BUILDT is Release 7.00 SP Level 10.0
SAP_BUILDT is Release 7.00 SP Level 0.0
All other components except for the Kernel are Release 7.00 SP Level 11.0 or 11.2
What could be wrong, and what can we do to solve it?
Best regards,
Robert Schulte

Thanks for your response, usha rani
1. We already tried that, unfortunately, it does not help
2. We checked the kernel version thoroughly after you suggested it, everything seems to be fine. We had a Unicode kernel before, and we still have one.
3. safemode is already set to NO
4. J2EE's default.trace is full of exceptions, but none of them is pointing me into a helpful direction.
Perhaps the exceptions mean more to someone else:
java.lang.Exception: Exception loading and instanciating sub-manager:
com.sap.caf.km.repositorymanager.CAFSecurityManager
(java.lang.ClassNotFoundException: com.sap.caf.km.repositorymanager.CAFSecurityManager)
com.sapportals.wcm.repository.runtime.CmConfigurationProvider#
sap.com/irj#com.sapportals.wcm.repository.runtime.CmConfigurationProvider.Component
<SetRoomIdForDiscussionObjects> will not be available.
Failed to load class
<com.sap.netweaver.coll.room.impl.filter.DiscussionSetRoomIdPropertyFilterManager>
#J2EE_GUEST#0####1e820b50fe4111db8e780013724175b4#SAPEngine_Application_Thread[impl:3]_22
##0#0#Error##Plain###
java.lang.ClassNotFoundException:
com.sap.netweaver.coll.room.impl.filter.DiscussionSetRoomIdPropertyFilterManager
com.sap.portal.prt.runtime.broker#sap.com/irj#
com.sap.portal.prt.runtime.broker#J2EE_GUEST#0####
1e820b50fe4111db8e780013724175b4#SAPEngine_Application_Thread[impl:3]_22##0#0#
Error#1#/System/Server#Java###
[PortalServiceItem.startServices] service initialisation failed:
tc.eu.odi.conn.uwl|OdiBridgeService
[EXCEPTION]
{0}#1#com.sapportals.portal.prt.core.broker.PortalServiceInstantiationException:
Could not instantiate implementation class com.sap.tc.eu.odi.conn.uwl.OdiBridgeService
of Portal Service tc.eu.odi.conn.uwl|OdiBridgeService because: could not load the service
com.sap.engine.services.deploy.container.ApplicationInManualStartUpException:
Application sap.com/com.sap.portal.fpn.accessservice cannot be started
because is in MANUAL start-up mode.
There are many more entries in default.trace.

JAVA Stack not starting up after System Copy

Hi,
We have done the system copy from Production to Sandbox and we are facing an issue with the JAVA Stack not starting up.
Following is the error in the SAPInst log file.
INFO
2014-09-07 18:06:48.86 [iaxxbfile.cpp:538]
CIaOsFile::chmod_impl(0755)
Authorizations set for /usr/sap/CS0/DVEBMGS00/data/icmandir/its/lsgui/images/list/symbols.
INFO
2014-09-07 18:06:50.494 [iaxxbfile.cpp:538]
CIaOsFile::chmod_impl(0755)
Authorizations set for /usr/sap/CS0/DVEBMGS00/data/icmandir/its/lsgui/js.
INFO
2014-09-07 18:06:50.819 [iaxxbfile.cpp:538]
CIaOsFile::chmod_impl(0755)
Authorizations set for /usr/sap/CS0/DVEBMGS00/data/icmandir/its/lsgui/js/texts.
ERROR
2014-09-07 18:06:55.22 [syxxcfsmgt.cpp:211]
CSyFileSystemMgtImpl::getNode(const CSyPath & path, CSyPath::NodeType nodeType) const
lib=syslib module=syslib
FSL-02015 Node /usr/sap/CS0/DVEBMGS00/data/stat46 does not exist.
INFO
2014-09-07 18:46:32.15 [iaxxbfile.cpp:538]
CIaOsFile::chmod_impl(0755)
Authorizations set for /usr/sap/CS0/DVEBMGS00/work/co.sapCS0_DVEBMGS00.
INFO
2014-09-07 18:46:35.895 [iaxxbfile.cpp:538]
CIaOsFile::chmod_impl(0755)
Authorizations set for /usr/sap/CS0/DVEBMGS00/work/dw.sapCS0_DVEBMGS00.
WARNING
2014-09-07 18:46:36.218
CJSlibModule::writeWarning_impl()
Broken link /usr/sap/CS0/DVEBMGS00/work/ig.sapCS0_DVEBMGS00 -> /usr/sap/CS0/DVEBMGS00/exe/igswd_mt detected.
Please guide.
Thanks,
CJ

For system of the J2EE stack did you use sapinst export and import ?
If the Java doesn't start then check the trace files (dev_server, std_server, bootstrap logs) present at /usr/sap/CS0/DVEBMGS00/work
Regards
RB

Mac OSX 10.6.2 Java 6 Web Start not always version checking on launch

When launching a Swing app via Web Start on Snow Leopard, it will often fail to discover and download the new version. This feature works consistently with Java 6 on Linux and Windows PC's.
The web-start app is accessed using an Application Bundle created with the Java Preferences app. If I clear the cache in Java Preferences, Web Start will nicely download the application and run it. However, after deploying a new version of the app, the Mac client will often run the cached version of the app without downloading the new version. Is anyone else experiencing this problem?

Re: "Alternatively, if you don't want to do this, the only other option I am aware of to solve this problem is to buy software like Fusion or Parallels and install Leopard (10.5) as your OS and run MX 2004 within a virtual environment."
Just so this is perfectly clear..... NO CAN DO
I have VMWare and Parallels on a Brand New MacBook Pro. It came with 10.5.11 and that is absolutely the OLDEST Mac OS I can install in a virtual environment. Believe me, I tried Tiger, Panther and Jaguar to no avail.
If the Mac in question came loaded with Snow Leopard, it has a "Snow Leopard or better" firmware write on the logic board and it will not allow an older OS to be installed.... even in a virtual environment, unless there's a secret that nobody I've spoken to in support for both VM clients knows.

Java won't start unless I kill some other processes; plenty of memory left

I am running Windows XP Pro (32-bits) with 4GB of physical RAM. XP reports 3.25GB of RAM. This is my desktop machine running IE7, Outlook, various other java or non-java apps. There are times when I cannot start another java application, even though TaskMgr reports Physical Memory Available at 2GB (or the Commit Charge is at 1.2 or 1.4GB.) If I kill IE7 or Outlook, for example, then the Java app will start and run fine. By the way, I have JRE 6update6 installed, though some (most?) Java apps have their own JRE included at various versions.
This is totally frustrating as I have all these available memory but I can't use it. Is there some tuning parameter in XP or JRE that I can set to allow me to use the rest of the memory? This might not be a Java problem but it is most apparent when I tried to start a Java app.
Thanks for your help.
Lawrence

32-bit Windows can address 4gB, no more; it reserves the last 2gB for itself, and loads applications only below 2gB. But there are additional constraints that typically restrict applications to less memory than that. When Java loads, it needs memory for it's own code, structures, stack, etc., in addition to the heap, which is the memory that your application uses for objects. In my machine (23-bit XP, SP2) the limit is 1322mB of heap memory (other options are default values.) You can find your current heap limit by running the java command with a -Xmx option, like this (the -version option is needed):
java -Xmx1322m -versionYou'll see either something like this:
java version "1.6.0_10-beta"
Java(TM) SE Runtime Environment (build 1.6.0_10-beta-b2
Java HotSpot(TM) Client VM (build 11.0-b12, mixed mode)or this:
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.depending on whether the requested contiguous memory can be allocated to Java.
If you want more information, it's available at the MS site, and there have been quite a few threads in these forums that also discuss it - search for them.

The target comp.java cannot be started because it is not a runnable target

I am using JDeveloper 10g (10.1.3.0.4 (SU4)) on Windows Server 2003. After compiling java program, when I try to run it, it gives following message:
"The target comp.java cannot be started because it is not a runnable target."
Could anybody help, what is problem? Do I have to make some configuration?
Thanks for reply.

if comp.java doesn't have a main method the surely it compile but will run since you need to a main method in order to run the your java program.

Any way to Initialize Java Array to start with 1

Hi Friends,
Is there anyway to initialize the java array with starting with 1 instead of normal 0.
Thanks and Regards.
JG

JamesGeorge wrote:
Hi Jacob,
Thanks for you time..
Coding like 1 - n will make everything uneasy, I find in other languages like vbscript,lotusscript it can be done..so just a thought to check in Java too..
Is there any valid reason for Java/Sun guys to start the arrays,vectors and other collections with 0
Thanks
JJShort answer: Java is a C-based language, and C arrays are zero-based so the rest are also zero-based for consistency.
Long answer: Arrays are implemented as contiguous areas of memory starting from a certain memory address, and loading from a zero-based array implies one less CPU instruction than loading from a one-based array.
Zero-based:
- LOAD A, ArrayAddress
- LOAD B, Index
- MUL B, ElementSize
- ADD A, B
- LOAD (A)
One-based:
- LOAD A, ArrayAddress
- LOAD B, Index
- ADD B, -1
- MUL B, ElementSize
- ADD A, B
- LOAD (A)

Learning Java - Where do I start

I would like to learn Java programming. I have solid background in OOP. Please let me know where I can start and how I can get hands-on experience
Thank you

You need both good programming tools and books:
1. download JDK131 from sun and install it;
2. download Forte for Java 3.0 from sun and install it;
3. download Java tutorial and other documents from sun
and read it.
then you can start.

New to Java, where do I start??!?!

Hello everyone, let me just introduce myself. My name is Jeff and I am from PA, I am a recent graduate of Penn State university with a bachelors of science in information science and technology, application/integration. My major dealt with alot of analysis/requirements/testing/planning/documentation, with a little bit of programming in such interfaces as HTML, CSS, ASP.Net, and I had one Java course which I could have done better in.
I started my career for a very large well known company in an entry level position. I went in with very little development skills, in the languages that we use here. Mostly everything is Java/Javascript, both of which I am pretty clueless about. They also do alot of web 2.0 stuff using ajax/xml/dojo. I just want to have some suggestions on how I could maybe learn this language a little better, I am not getting anything really so far, because ive just been doing e-learnings and such. I want to start shadowing the developers, but I dont want to go in seeming stupid! Who has some suggestions?

Hi and welcome.
This is the beginner's set:
[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.
JavaRanch
To quote the tagline on their homepage: "a friendly place for Java greenhorns." FAQs, forums (moderated, I believe), sample code, all kinds of goodies for newbies. From what I've heard, they live up to the "friendly" claim.
[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.com/Effective-Java-2nd-Joshua-Bloch/dp/0321356683]
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.amazon.com/Java-TM-Programming-Language-4th/dp/0321349806/ref=sr_1_1?ie=UTF8&s=books&qid=1247059012&sr=1-1]
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/]

Java: Where are JCE Unlimited Strength Jurisdiction Policy Files for Java for Mac OS X 10.7?

I need to install the JCE Unlimited Strength Jurisdiction Policy Files for Java 1.6 under Mac OS X 10.7. I know where to get then from the Sun/Oracle Java download site, but want to make sure that these will work on the Mac. Or, are there Mac specific versions somewhere?

There's a jce.jar file in /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home/lib/, so it appears that they're already in place, but that's just a WAG.

Java: where do I download it from?

I can't tell if Java is installed on my computer, but when I clicked on a coupon today to print it, I got an error message saying Java wasn't available so I couldn't print. I tried downloading the latest update, but no luck. I think I need to download the whole Java program, but where can I download Java from?

Java should install under Software Update. If it doesn't you can download Java for Mac OS X 10.5 Release 10 here: http://support.apple.com/kb/DL1359 (direct download: http://support.apple.com/downloads/DL1359/en_US/JavaForMacOSX10.5Update10.dmg). I believe the prerequisite for Release 10 is Release 5, which you can download here: http://support.apple.com/kb/DL924 (direct download: http://support.apple.com/downloads/DL924/en_US/JavaForMacOSX10.5Update5.dmg). Let us know how it turns out.

Handling sql query in java where i'm extracting reords from 3 tables

hi to one and all,
i want to implement the sql query given below in jsp in execute query statement . the query is working in sql but not when implemented using jsp. please help me in resolving this.
Query
SELECT e.Department , e.ETitle , s.basic , s.da, c.address1 , c.address2 from Employee e , Salary s , Contactdetails1 c where e.id = s.id and e.id =c.id

It would help if you gave us a little more info to go on like;
a) post your code
b) post the error message the compiler is giving you

Oracle Packages for Java, where to get

Hi, I've a problem because the oracle packages aren't installed on my workstation so I'cant register a driver to gain access to my database.
Can anybody tell where I can download only the needed packages??
thx

Problem already solved.
I found some little Oracle.jar whitch contains everything needed.

Java?!?! Where to start, where to go!

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