I'm just starting to use swing in java, and I've come across a weird problem. I'm trying to add a splash screen (http://wiki.netbeans.org/Splash_Screen_Beginner_Tutorial), and everything works fine until I add splash:src/Splash.png to my VM options. Once I do that, I get this error:
Error: Could not find or load main class splash:src.splash.png
Java Result: 1
It's as if java is trying to find my main class inside the png file??? I believe my file is in the correct place, this is what it looks like:
And my main.java is just a default swing frame form. Any clue whats going on?
Thanks!
Edit: New file layout:
Changed manifest and VM settings, same error: Error: Could not find or load main class splash:images.splash.png
Java Result: 1
From the error you've listed, it looks like you've missed the - from the splash vm option. This means the command line will be:
java splash:src.splash.png Main.class
Means the Java executable thinks you're asking it to run splash:src.splash.png.
The command line should be (note, you don't need to include the src directory):
java -splash:images/splash.png Main.class
Check your VM Options in Netbeans and correct it to -splash:images/splash.png.
I strongly suggest you puting files other than .java (source files) in another directory. In the most common case src is where Java IDEs (at least Eclipse and NetBeans) put the source files, it is pretty much standard, and the hierarchy of the folder inside it has to match your Java packages names. So, move the image to another folder, let's say img and try again.
Related
I currently don't have a working way to edit and run Java on my computer, so I'm trying to get Atom working with Java (I realize it's not a Java IDE and I'm not trying to make it one, I just want to be able to do some light Java work on my laptop). I've installed the script and instant-build packages for Atom and wrote the following test code in a file called "main.java' in my project folder:
class Main{
public static void main(String[] args) {
System.out.println("please");
}
}
When I try to run the code with cmd+i (I'm on a 2012 MacBook Pro) and get the following error message:Error: Could not find or load main class main.
I'd be happy to provide any further information; thanks for helping!
The huge problem of learning Java is that you need to launch the projects in a very strict way, and setting the classpath is always problematic. The solution lays in the following (pretty enigmatic) line of the "Script" documentation:
Project directory should be the source directory; subfolders imply packaging.
So, instead of opening a plain file, open the project (folder) with .java classes or define inside the file, the package to which your .java belong.
It's due to the fact that JDE needs to create a virtual target in form of .classess and single .java file definitely can't be launched as standalone file. I suppose that "Script" is not able to locate the source folder when you try to execute seperate .java file.
Before launching your .java files always "Add Project Folder..."
Please remember that it's not possible to have several folders opened if they don't belong to the same project. Such situation cause problems of locating the right classpath and in the end javac prompts the error.
You have to name your file with the first letter in upper case Main.java, since it must match the name of your class
I replicated the issue quite easily. If I created a new directory in Atom itself and then tried to run the code it didn't work as your error message came up for me as well. Error: Could not find or load main class main.
I used an existing directory and then created a file inside that folder in Atom and ran the same code it worked. I then copied and pasted that same file into the directory of my choice and it worked.
I'm running some tests on a software tool on some java classes from the command line and its asking for classpath of a class in this format: "-classpath _____". I have attached and image here and would greatly appreciate if someone can take a look at it (the most recent tries are on the bottom, and I'm mousing over the java class I'm trying to run the software tool on in Eclipse to the top right).
Image: The directory is shown on top left of screen on the title bar of eclipse.
You can see at the bottom of the command line that my most recent attempt and the messages that it's replying that its an unknown class and for me to make sure its the correct classpath.
For the class I have to put after '- class' and I have put '-class CBranchExample' as my class is CBranchExample.java.
For the classpath I thought it meant directory its stored in: C:\Users\Kranti\Desktop\evosuite-master\master\src\test\java\com\examples\with\different\packagename\cbranch, and so I put in the command line: 'CProject C:\Users\Kranti\Desktop\evosuite-master\master\src\test\java\com\examples\with\different\packagename\cbranch'.
But there are still errors, but its not a fatal error that only appears if I put a random classpath or the wrong syntax for a class.
Edit: I mean in other words, what is it asking for when it's asking for CLASSPATH when I've already tried the directory of the place I saved my class?
From documentation: http://www.evosuite.org/documentation/commandline/
Here is a working example:
java -jar evosuite.jar -class [inner class] -projectCP [Full path + filename + .jar]
The following will open TestProject.jar form the same folder and target the MyTest.Test class.
java -jar evosuite.jar -class MyTest.Test -projectCP ./TestProject.jar
So I'm completely new to programming, and I've been writing some Java with the NetBeans IDE. My code runs fine within NetBeans, but I've tried to run it using the command line as well. However, if I run it from the command line, I have to delete the line:
package firstprogram;
which NetBeans automatically places at the top of each new file, or I get the error:
Error: Could not find or load main class FirstProgram
However, if I do delete the line, then the program no longer runs within NetBeans! It doesn't seem right that I have to choose whether to run a .java from within NetBeans or without.
The research I've done makes me think that this is something to do with directory structure? But everything I read on that goes straight over my head. NetBeans has a structure with "build", "dist", "nbproject", and "src", but when I use the command line I just place the .java file in an empty directory and javac from there.
Any explanation is appreciated! The books and tutorials I'm learning from either assume you're just using NetBeans or don't have the package line at all.
You can compile your class using javac command from anywhere, as long as you provide correct relative or absolute path. The problems come when you want to run your program using the java program.
You have to provide the correct path corresponding to your package declaration. For example, if I had 'MyClass' in package mypackage, first line would look like this:
package mypackage;
class source stored on disk:
c:/MyNetbeansProject/src/mypackage/MyClass.java
Compiled bytecode:
c:/MyNetbeansProject/build/classes/mypackage/MyClass.class
Now, if I would have opened a command prompt/terminal in folder c:/MyNetbeansProject/build/classes/, I could run the program using java mypackage/MyClass or java mypackage.MyClass.
However, if i would be somewhere else, I would have to say where the class files are located using the cp option: java -cp c:/MyNetbeansProject/build/classes mypackage/MyClass. The path in cp option can be relative or absolute, use "" when it contains spaces.
Package are directory architecture.
If your class is in the package com.acme.test, the class should be in the com/acme/test directory.
Instead of placing your class in an empty folder, place it in a folder named firstprogram and do javac firstprogram/youclass.java
The package (and folder) permit you to arrange your architecture with logical pattern.
More info here : http://www.tutorialspoint.com/java/java_packages.htm
So like OcterA said, you should keep organized, but with only one class this is not the issue. I believe that your problem is that you are not entering the correct command into the command line.
First cd to the correct directory and when you want to execute a file within a package in that directory you need to enter
java packageName.className
In this case
java firstprogram.FirstProgram
Ok, I'm stumped here. I'm using Matlab version 2013b with a Java RTE of 1.7.0_11 and I'm trying to run a simple piece of code to see if Matlab is able to read the .jar file and nothing seems to be working.
Here is the Java code, which is compiled to a .jar named JavaOCT.jar, which is placed in the Matlab working directory:
package VTK;
public class vtkVolumeView{
public int Test(){
return 10;
}
}
That is it, no other dependencies, nothing fancy. In Matlab, I try:
javaaddpath('\JavaOCT.jar'); %<-Directory and name are 100% correct
import VTK.*; %<-Package name from above
methodsview VTK.vtkVolumeView; %<-Can't find the class, argh!
Matlab kicks back that it can't find the class.
Things I've done to try and solve the problem:
Reverted to the exact same JDK as the Matlab RTE
Tried an older 1.6 JDK
Done lots of stack overflow research to try and solve it 1 2 3 4
Tried used javaclasspath and pointing to the compiled class instead
Read the Matlab documentation 5
Using clear -java after the javaaddpath
Any help would be appreciated, it is driving me nuts!
Update: Daniel R suggested just javaaddpath('JavaOCT.jar') which doesn't work either.
Final update: It finally works! I wasn't building the .jar properly. In IntelliJ, click on the project and hit F4. This brings up the Project Structure, then go to Artifacts and click the green + button and add DirectoryContent and then point to the out\production. Once this is done, as mentioned by others, it should show up in Matlab as an expandable .jar.
I don't know which operating system you are using, but the ./ seems invalid.
Try javaaddpath('JavaOCT.jar'); or javaaddpath(fullfile(pwd,'JavaOCT.jar'));.
What does exist(fullfile(pwd,'JavaOCT.jar')) return?
Some things to try:
Add the class file. When using a package, you need to add the class file in at the host of the package. For example, if your code is here:
\\full\path\to\code\VTK\vtkVolumeView.class
Then use:
javaaddpath('\\full\path\to\code')
I'm still suspicious of your *.jar path. You should usually use absolute paths when adding jar files. Try adding the results of which('JavaOCT.jar')
How did you make your jar file? Does it contain the appropriate directory structure implied by your package declaration?
I have been searching the web trying to find the answer to my question, but everywhere I look seems to have too complex of a solution for a beginner like me. I have been working on this project, and just now realized that I should've made a package, or something like that. The thing is though, my program was working fine until I started dabbling with it, and now it won't work at all. I am getting this error:
Exception in thread "main" java.lang.NoClassDefFoundError: BubbleSort. class
Caused by: java.lang.ClassNotFoundException: BubbleSort.class
at java.net.URLClassLoader.findClass(URLClassLoader.java:434)
at java.lang.ClassLoader.loadClass(ClassLoader.java:672)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:358)
at ``java.lang.ClassLoader.loadClass(ClassLoader.java:638)
Could not find the main class: BubbleSort.class. Program will exit.
Here's how my "path" looks, if I am not mistaken. I am connected to my school's Z: drive through a remote connection, and from there I have a folder called myFirstname_Lastname_A4,
which then leads me to another folder called sortingzz which I believe is supposed to have only my source files, but it also ended up with my class files in there whenever I compiled. So here's what I am doing to compile.
cd myFirstname_Lastname_A4/sortingzz
javac *.java (Works fine, this is where I end up with my Class files inside of my sortingzz folder)
java * (This is where I get the error)
I am pretty sure I am just trying to run the program wrong. Before I started messing around with stuff I wasn't ready for, I used to just run the file with my main function in it, like this
javac SortingImplementation.java
java SortingImplementation
And that for the most part worked fine, but I started having trouble calling certain classes from other classes, so thats when I found out I was suppose to do the packaging and importing stuff.
In case that is the issue, I have on the top line of every source file:
package sortingzz;
and I am importing like this:
import sortingzz.*;
This is correct, right?
UPDATE:
I decided to give up on class pathing and trying to package everything, because as usual, I am getting responses that are way over my head, and to be honest I don't think it is necessary.
After removing package and importing from everything, and once again compiling using javac *., it actually compiles this time. However whenever I try to run my class with the main in it, SortingImplementation, it tells me that
Could not find the main class: SortingImplementation. Program will exit.
I don't get it, I am looking at the SortingImplementation.class right now, with all the other classes and java files, so I am not sure what it's trying to do.
javac *.java is fine. This will compile your files. However, you only need to run the file with your main method in it: java MainClass
You say that you are using packages to organize the classes. In this case you need to set the class path using the -cp flag.
javac -cp /path/to/parent/of/package classname.java
and
java classname
Also, your main class should be declared public and should have a main()
NoClassDefFoundError occures when a class was recognised in compile time but was not available during runtime.
So the JVM can't find your class in the classpath.
using -cp flag to specify where your package is should work.
the commanc javac *.java compiles all found java files to corresponding .class files. If you all your classfiles are in the same folder, which they should, you just run your regular java SortingImplementation command.
java * would, a bit depending on your OS, yield in an undesired command. For instance, on Linux it would be expanded by the OS to java SortingImplementation.java SortingImplementation.class BubbleSort. The last one is a directory, which ofcourse is not an executable class.