Develop Reference

Why cannot run compiled JavaFX 11 class?

Following instructions at https://openjfx.io/openjfx-docs/#install-javafx, I compiled the sample HelloFX.java via:
javac --module-path $PATH_TO_FX --add-modules=javafx.controls /Users/me/Documents/java/HelloFX.java
But now if I attempt to run that...
java --module-path $PATH_TO_FX --add-modules=javafx.controls /Users/me/Documents/java/HelloFX
... I get error:
Error: Could not find or load main class .Users.me.Documents.java.HelloFX
Caused by: java.lang.ClassNotFoundException: /Users/me/Documents/java/HelloFX
Yet the file reported as not found is there:
ls -l /Users/me/Documents/java/HelloFX.class
-rwxr--r-- 1 me staff 1336 Oct 30 16:01 /Users/murray/Documents/java/HelloFX.class
(I had already changed permissions to add u+x in case that was the issue, but apparently that was not the trouble.
What's wrong?
(Yes, $PATH_TO_FX does point to javafx-sdk-11/lib.)

This question was already answered in the openjfx-dev mailing list:
The "java" command expects a fully-qualified class name, not a file path as
its argument
For completion:
The javac command deals with filenames, which means you can compile a java file from any location:
javac [ options ] [ sourcefiles ]
However the java command deals with classes:
java [options] mainclass [args...]
where mainclass specifies the name of the class to be launched, not the filename or location.
Providing you have Java 11 installed (and JAVA_HOME is set at it), the JavaFX 11 SDK downloaded, and just following the getting started guide:
Download the HelloFX class to any location, i.e /Users/<user>/Downloads.
Open a terminal and cd to that location:
cd /Users/<user>/Downloads
Set the JavaFX path:
export PATH_TO_FX=/path/to/javafx-sdk-11/lib
Compile the class:
javac --module-path $PATH_TO_FX --add-modules=javafx.controls HelloFX.java
Check that HelloFX.class is created at the same folder level.
Run the class:
java --module-path $PATH_TO_FX --add-modules=javafx.controls HelloFX
It should run just fine.
Now, if you try to run the above command from a different location it won't work, because the HelloFX class is not available in the classpath.
So if you want to run this class from a different location you'll need to specify this classpath:
javac --module-path $PATH_TO_FX --add-modules=javafx.controls \
/Users/<user>/Downloads/HelloFX.java
java --module-path $PATH_TO_FX --add-modules=javafx.controls \
--class-path /Users/<user>/Downloads HelloFX

Crontab java.lang.ClassNotFoundException with a jar file

#!/bin/bash
JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_60.jdk
CLASSPATH=/Users/sunny/CronTest/out/production/CronTest
$JAVA_HOME/Contents/Home/bin/java -cp $CLASSPATH ".:/Users/sunny/Downloads/sqlite-jdbc-3.8.11.2.jar" sample.Main
exit 0
Sqlite jar file is in /Users/sunny/Downloads/sqlite-jdbc-3.8.11.2.jar
Compiled java class file is in /Users/sunny/CronTest/out/production/CronTest/sample/Main.class
And I've set the cron job to be schedule at every 1 minute. Java class is getting exucuted but I am getting java.lang.ClassNotFoundException: org.sqlite.JDBC
Same command which is in script is working in terminal.
My question is how can I add jar file properly to be executed from shell script.

Seems there is a space in between your $CLASS PATH and ".:/Users/sunny/Downloads/sqlite-jdbc-3.8.11.2.jar" and missing a colon(:).
Please try with following with export:
export CLASSPATH=.:/Users/sunny/CronTest/out/production/CronTest:/Users/sunny/Downloads/sqlite-jdbc-3.8.11.2.jar
and call java command with -cp $CLASSPATH.
If it still not work, please try with -cp directly:
$JAVA_HOME/Contents/Home/bin/java -cp ".:/Users/sunny/CronTest/out/production/CronTest:/Users/sunny/Downloads/sqlite-jdbc-3.8.11.2.jar" sample.Main

Putting servlet jar in CLASSPATH in windows 8.1

I'm trying this on cmd:
javac -classpath .;C:\Users\Myname\Documents\Tomcat_Apache\apache-tomcat-8.0.20\lib\servlet-api.jar ;C:\Users\Myname\Documents\Tomcat_Apache\apache-tomcat-8.0.20\webapps\mybay\WEB-INF\lib\jsp-api.jar
I'm getting this :
javac: invalid flag:
C:\Users\Myname\Documents\Tomcat_Apache\apache-tomcat-8.0.20\webapps\mybay\WEB-INF\lib\jsp-api.jar
Usage: javac 'options' 'source files'
I need this in order to use extends HttpServlet in java.
Can you help?

Java - NoClassDefFoundError on running

Today I tried to compile my sources through the command prompt:
PS ...\JavaDev\Prog> javac -classpath <libs> -d . -sourcepath src src/com/negi/prog/Prog.java
They compiled successfully.
But when I try to run it, it produces an error:
PS ...\JavaDev\Prog> java -classpath com.negi.prog.Prog
Exception in thread "main" java.lang.NoClassDefFoundError: com/negi/prog/Prog
Caused by: java.lang.ClassNotFoundException: com.negi.prog.Prog
How can I fix that?

The classes in your -classpath have to be separated by :
PS ...\JavaDev\Prog> java -classpath "<libs>:com.negi.prog.Prog"
To complete the answer, the different operating systems have different classpath separators. You can check the separator by retrieving the value of the java.class.path property.

By default . (current path) is included in class path, but if you specify -classpath or -cp, then that is overridden. Include . in your classpath:
java -classpath <libs>:. com.negi.prog.Prog

You need to ensure the current directory is on the classpath when running i.e.
PS ...\JavaDev\Prog> java -classpath <libs>:. com.negi.prog.Prog

"error:cannot acces com.hello.LibC","Class file for com.hello.LibC not Found"

I am new to Android.I use this link to run the NDK Project.
I follow all these steps from the given link.However during compilation in the command prompt it shows error like:
$ javah com.hello.LibC
error: cannot access com.hello.LibC
class file for com.hello.LibC not found
javadoc: error - Class com.hello.LibC not found.
Error: No classes were specified on the command line. Try -help.
please help me.
Thanks in Advance.

you need to specify the classpath using -classpath PATH option when running javah inside bin directory of your project:
$ javah -classpath classes/ com.hello.LibC
also you can specify the output directory using option -d PATH
$ javah -d ../jni -classpath classes/ com.hello.LibC