Running java from command line with packages: NoClassDefFoundError - java

I had a fully functional Java program that I am now trying to put into a package instead of having it in the default package. All of the .java files are in the mymap package, and I am trying to run black box tests in my MyMapTest.java file. The problem is that I don't know how to properly run this in the command line now that I have it in a package. I got stuck trying to google for answers.
I can get it to compile:
javac -cp "../junit.jar" *.java;
But when I try to run it as I previously had...
java -cp .:../junit.jar org.junit.runner.JUnitCore MyMapTest
I get the error java.lang.NoClassDefFoundError: mymap/MyMap for all of my tests. I guess the issue is that somehow I am not properly including mymap, perhaps in the classpath?
Similarly, I also have white box tests in MyMapWhiteBoxTest.java, where this file is also in the mymap package. I cannot figure out how to properly run these tests either. Trying to run it the same way, I get:
Exception in thread "main" java.lang.NoClassDefFoundError: MyMapWhiteBoxTest (wrong name: mymap/MyMapWhiteBoxTest)
For both cases, I have tried mymap/FILE or somehow also including the package in the classpath, but I'm definitely missing something.

If the main() is present in MyMapTest class then you can try the below command :
java -cp .:../junit.jar org.junit.runner.JUnitCore myMap.MyMapTest

After compilation: (javac -cp "../junit.jar" *.java;) what do you have in your current dir? You should have the file ./myMap/MyMapTest.class.

Related

unable to compile and run a java program with multiple source files on the command line

I am trying to compile and run a java program that has 3 source files, and I am not able to get it to run.
I have a folder with 3 java source files, Tester.java, CommandHandler.java, and DualList.java. Tester.java contains the main function, and depends on CommandHandler.java, which depends on DualList.java
I tried to compile the program with javac Tester.java CommandHandler.java DualList.java. It created the three class files, but when I try to run the program with java -cp . Tester I get the following error:
Error: Could not find or load main class Tester
Caused by: java.lang.NoClassDefFoundError: cmsc420_s22/Tester (wrong name: Tester)
I can see that the class file is there, and I got no errors during compilation, so I'm not sure what is going on. I think it might be a problem with my java installation or my configuration. I'm doing this on a kali linux WSL distribution. I haven't changed anything about my installation, and I set my classpath to the current folder so I'm not sure what's wrong
Thanks

Could not find or load main class Javac

Quick note, I went through every single other question through here and nothing seems to work.
So, here is my issue. All I want to do is create a windows batch script that will be used to execute my selenium project on Jenkins. Sounds simple right ? Its probably is, but I am missing something...
Here is my project https://github.com/Daviditooe/Nomad
First command I tried:
javac src/nomad/execute/Execute.java
Execute.java:9: error: package nomad.sites does not exist import nomad.sites.MmaShare;
It also couldnt find any of the jars, so I add all of them
Then I tried:
javac -cp Jars\* src\nomad\execute\Execute.java
This fixed the jars issue but the package not found still exists
So then I tried compiling every single package at the same time
javac -cp Jars\* src\nomad\execute\*.java src\nomad\actions\*.java src\nomad\baseactions\*.java src\nomad\browsers\Chrome.java src\nomad\directory\*.java src\nomad\scripts\*.java src\nomad\sites\*.java src\nomad\urltools\*.java
So, now its not crashing, then I tried compiling...
java src\nomad\execute\Execute
And its giving me Could not find or load main class
So That last thing I tried was compile all of them at the same time.
java src\nomad\actions\MmaShareActions src\nomad\baseactions\BaseActions src\nomad\browsers\Chrome src\nomad\directory\Directory src\nomad\execute\Execute src\nomad\scripts\Vpn src\nomad\sites\MmaShare src\nomad\urltools\UrlTools
Still no luck... anything thoughts would be appreciated.
Again: You must go into the src folder before you execute javac and java!
I can compile and execute it on my Linux Laptop:
stefan#stefanpc:/hdd/stefan/Downloads/Nomad-master/src$ javac -cp '../Jars/*' nomad/execute/*.java nomad/actions/*.java nomad/baseactions/*.java nomad/browsers/Chrome.java nomad/directory/*.java nomad/scripts/*.java nomad/sites/*.java nomad/urltools/*.java
Note: nomad/baseactions/BaseActions.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
stefan#stefanpc:/hdd/stefan/Downloads/Nomad-master/src$ java -cp '../Jars/*:.' nomad.execute.Execute
Exception in thread "main" java.lang.IllegalStateException: The driver executable does not exist: /hdd/stefan/Downloads/Nomad-master/src/C:\Users\Davidito\Desktop\AutoLinks\Jars\chromedriver.exe
Of course my Linux machine does not have the chromedriver.exe installed.
Under Windows, you must use "\" instead of "/" and you must use ";" instead of ":". Note that you must add the current folder "." to the class path when you execute the program. Otherwise java would only search in the Jars folder.

Why can't I run java from the command line anymore?

I've been running java programs from the command line for 5+ years using the same process:
javac Program.java
java Program
This is suddenly not working. Compiling works, but when I try to run the program I get an error saying the class cannot be found.
However, now when I type this, it works:
javac Program.java
java Program.java
This is fine, but when I have a class that extends another, it isn't being found.
Here is how it looks on the command line:
C:\Drive\Java>javac Program.java
C:\Drive\Java>java Program
Error: Could not find or load main class Program
Caused by: java.lang.ClassNotFoundException: Program
C:\Drive\Java>java Program.java
Hello World
Is there something I could have done to cause this change? I noticed it started happening yesterday after a windows update.
The Class's name should be exactly the same with the file name, please paste the code or check it yourself.
I was able to resolve this issue. The problem was that I had added a CLASSPATH environmental variable that pointed to my java bin folder and this was causing the behavior. I deleted it and the problem was resolved.
I suggest you check if your computer system is compatible with your jdk version.
And support? x86 x64

"java.lang.ClassNotFoundException: oracle.jdbc.driver.OracleDriver" error when running from terminal

I have a program that I run from Eclipse successfully.
However, when I want to run it from terminal, I encounter the famous error:
"java.lang.ClassNotFoundException: oracle.jdbc.driver.OracleDriver"
on this line:
Class drvClass = Class.forName("oracle.jdbc.driver.OracleDriver");
PS:
I have the following in CLASSPATH:
/oracle/jdbc/lib/ojdbc6.jar
Also note that I compile it successfully (javac Test2.java). Then when I run it (java Test2), I get the following error:
Error: Could not find or load main class Test2
So I run:
java -classpath ~/Desktop/JDBC2/src Test2
It runs, but I get the above "ClassNotFoundException" though.
I found this question tricky: the reason is related to semicolon after jar file address.
At first I changed the directory of MySample.java to another directory (you can don't do that) like C:\
then I removed package address from the source code, at the end I run this command in cmd
java -cp path_to_oracle_driver.jar; MySample
P.S. If you want run it from terminal you have to remove package PackageAddress from the source code and compile it again.
As #yngwietiger mentioned above in the comments, using -classpath parameter when running the .class file, overrides the original CLASSPATH and the predefined ojdbc6.jar file. So we need to mention both when running:
java -classpath ~/Desktop/JDBC2/src:/oracle/jdbc/lib/ojdbc6.jar Test2
Or, as a better solution, we can add the current path to CLASSPATH (note the colon and dot at the end):
export CLASSPATH=$CLASSPATH:.
And, in order to run, we just need to type:
Java Test2

Cannot run simple compiled java program?

I am on Arch Linux, I just installed JRE and JDK and all the proper bin files (javac and java) are in /opt/java/bin/
I simply compiled a standard hello world, and compiled it with javac running javac ./hello.java and that made a class.
Now my problem is running it. I run java ./helloworld.class and it gives me an error, even if the file I point java to is non-existant:
Exception in thread "main" java.lang.NoClassDefFoundError: //helloworld/class
Caused by: java.lang.ClassNotFoundException: ..helloworld.class
(..omitted for clarity..)
Could not find the main class: ./helloworld.class. Program will exit.
You will notice the first line of the error, it munges the path //helloworld/class
When I feed java an absolute path, i.e java /home/foo/helloworld.class it gives the same error, but replaces the path's / with . in the first line, again munged.
What do you think is wrong? I really don't know why it is doing this..
When you run java, you just pass it the fully qualified class name (including package), not the file name.
java helloworld will look for helloworld.class.
java helloworld.class will look for helloworld/class.class
You do not run a file as
# java file.class
you run it as
# javac PATH/file.java
# java PATH/file
Do not add .class while using JAVA command.
Actually you should compile it like this
javac helloword.java
run the program
java helloword
And yet another thing: add command line option "-classpath ." or it short version "-cp .", i.e. your command line should look like:
java -cp . helloworld
this is if your class is in your current directory. Otherwise "." should be replaced by path where the class(es) may be found.

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