Develop Reference

Running multiple Java classes

I am trying to run a code with multiple Java class files and a jar file which is from a library I downloaded. I compiled them with the following:
javac -cp "quickfixj-all-.jar" BTCCMarketDataRequest.java Bot.java
The Bot class has the main method and the BTCCMarketDataRequest file has a bunch of other methods in the class. I am not creating any packages.
How should I run it though?
If I do:
java Bot
I get the following output:
Exception in thread "main" java.lang.NoClassDefFoundError: quickfix/Group
at Bot.main(Bot.java:4)
Caused by: java.lang.ClassNotFoundException: quickfix.Group
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
... 1 more
The compiled class (the one in the jar file could not be found, but why? I compiled it.
I am new to Java so I have no idea what's going on.
Thank you!

You need to add the classpath while executing the program as well.
java -cp .:quickfixj-all-.jar Bot
This assumes that the Bot class is in the default package and all the jar and .class dependencies are in the same directory.

Error when starting example code in JPVM

I am trying to run the example code provided with the JPVM,the java version of PVM.
I am able to start the JPVM daemon without any errors but when I try to run the example provided I get the following error:
Exception in thread "main" java.lang.NoClassDefFoundError: jpvm/jpvmException
Caused by: java.lang.ClassNotFoundException: jpvm.jpvmException
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: hello. Program will exit.

I was running the examples from the examples directory, I copied the .class files into the JPVM root directory and ran them from there and it worked.
apparently the jPVM root directory is the working directory and examples need to be ran from there.

when running the java program, report cannot find class

The file FactoryDemo.java is compiled successfully and in it there is the
package home.city.Desktop.factorydemo;
I compile it by using javac -d / FactoryDemo.java and nothing wrong is reported.
But when I try to run it by using java home.city.Desktop.factorydemo.FactoryDemo, it reports：
Exception in thread "main" java.lang.NoClassDefFoundError: home/city/Desktop/factorydemo/FactoryDemo
Caused by: java.lang.ClassNotFoundException: home.city.Desktop.factorydemo.FactoryDemo
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: home.city.Desktop.factorydemo.FactoryDemo. Program will exit.
I have tried many times but I could not find the solution to the problem. Thanks for your help in advance.

Your compiled class must be in a directory called:
home/city/Desktop/factorydemo
On Unix, just run this:
mkdir -p home/city/Desktop/factorydemo; mv FactoryDemo.class home/city/Desktop/factorydemo/
For best practice, simply move your Java source file in that folder too so the compiler outputs the file to the right spot.

FactoryDemo Class is created under root directory, you should type following command ( . instead of /)
javac -d . FactoryDemo.java
It creates home.city.Desktop.factorydemo directories starting from current directory.
If you want class created under root directory. You must type following command to execute.
java -classpath / home.city.Desktop.factorydemo.FactoryDemo

Ant Build File Configuration

Using Ant to compile simple Hello World program in Java, and something isn't working right. I know the Java code is correct, as it runs using javac. Something is wrong with my Any config file, and I can't quite figure out what it is. http://pastebin.com/q50L5b0D
and the command line errors I'm getting:
**Exception in thread "main" java.lang.NoClassDefFoundError: Proj0/class
Caused by: java.lang.ClassNotFoundException: Proj0.class
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: Proj0.class. Program will exit.
**

It just tell you the class Proj0 could not be found when trying to run your application using the ANT target you defined. Are you sure this line is correct ?
<property name="Proj0.class" value="package.names.Proj0"/>
The package.names.Proj0 is a strange name for a package, maybe you wanted something like using the actual value of a property called package.names?

For your javac task need to set the classpath , srcdir properly. As Vincent wrote you are missing the Proj0 class. Please look here for how to set the javac task.

java runs fine with 'absolute' path, doesn't run with CLASSPATH specified

my program is in package pl.edu.uj.tcs.crazySocket; due to some requirements. I work in the crazySocket directory. In order to compile the program I use command
CLASSPATH=~/prog/colosseum/data javac tictactoe.java
and that succeeds. I want to run the program. I change javac to java and get rid of the '.java'. I get
Exception in thread "main" java.lang.NoClassDefFoundError: tictactoe
Caused by: java.lang.ClassNotFoundException: tictactoe
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
when I get up in the tree directory to the ~/prog/colosseum/data and run java pl/edu/uj/tcs/crazySocket/tictactoe all works fine.
What's wrong with the CLASSPATH? Shouldn't it work both with javac and java?

There's nothing wrong with your classpath, it's your call to java that's wrong.
You need to specify the full qualified class name pl.edu.uj.tcs.crazySocket.tictactoe.