So, I have checked some other threads that are about this topic, such as the following:
Eclipse says package declaration does not match expected package ""
The declared package test does not match the expected package
libgdx: The declared package does not match the expected package ""
But they all deal with Eclipse (or Eclipse + Maven), and I am just using VS Code without all the fancy capabilities of an IDE or a package manager.
As the title suggests, I am getting the message:
[Java] The declared package "controller" does not match the expected package ""
I get this message for every single file that I attempt to give a package using the syntax:
package myPackageName;
even if the file in question is defiantly in the right folder. This problem only occurs as a visual, i.e. everything compiles fine using javac. I have been dealing with it ever since I started using VS Code for my Java Projects.
How do I make the red squigglies and the red lettering in the file explore tab go away in the case of perceived package errors?? It drives me nutty, I can't quickly find the files that actually have errors in my project because everything is marked red except the Driver.
Here is a picture: picture
[edit] Got rid of the unrelated compile time errors So you can see it compiles.
All classes in the package should be open on VSCode (on different tabs).
Same thing happens when you want to use other public classes in same directory: it should be visible but when you run the program, you will get a compile-time error. Then again the solution is to have all classes open on different tabs.
Hope it helps
A bit late to it, but here is my finding:
Your parent folder is proto9, so in all your child folders, i.e. controller, model and view. You should write package proto9.controller, package proto9.model etc. You can compile the .java file just fine in the correct directory, but not 100% sure why we cannot run it while in the directory of the file is at, java.lang.NoClassDefFoundError is returned when attempted so.
To successfully run it, in the terminal (assuming your files are compiled):
# cd one level out of your parent directory
PS C:\Users\Issac\Dropbox\Apps\Celerious Text\proto9> cd ..
PS C:\Users\Issac\Dropbox\Apps\Celerious Text> java proto9.controller.MainController
...
PS C:\Users\Issac\Dropbox\Apps\Celerious Text> java proto9.view.MainView
etc.
Hope this works for you as well!!
Related
I want to use my "Final_Frame.java" in my "SampleFrameProject.java", sort of like interconnecting it by creating a "Final_Frame" object and then typing the "this.show()".
However, an error message appears, saying that "package com.toedter.components does not exist." That is the only error I've seen; I'm confident that my "Final Frame.java" is functioning well before I copy-paste it, hence I knew the issue was caused by my copy-pasting.
Btw all of the error is pointing to JCalender, and JComponents, I'm pretty sure I followed the instructions while installing them. They are working just fine before I move the "Final_Frame.java", but after I move it, it began to show errors. So is there any way for me to copy-paste it correctly? or are there any methods to call "Final_Frame.java" inside my "SampleFrameProject.java" without copy-pasting?
Thank you in advance!
package is a fundamental concept in Java. It is nothing but a namespace for the Java source file, reflecting the directory (folder) structure of your project after the src/main/java directory.
package is usually defined at the first line of the file. For example, given the directory structure from your root directory mavenproject2, the directory structure inside if it is src/main/java/com/foo/bar/FinalJava.java, then the corresponding package defined will be
package com.foo.bar;
// imports
public class FinalJava {
// the content of class
}
For your case, it would seem that you have copied com/toedter/components/FinalFrame.java from the Hotel_Management_System project (which already has defined a line package com.toedter.components in the file) to another project mavenproject2 which has a different directory structure (which is not clear in your question).
The solution would be to modify the package line according to your directory structure then it would solve the error.
Personally, I would suggest to learn some basics in Java, take some tutorials, or at least write some simple Java console applications before diving into GUI applications.
I'm trying to learn how to set up a GUI layout, so I'm reading through this page, which has this example code.
The problem is, when I run the code (either through Geany or the command line), it seems to compile correctly, then it gives me this error when I try to run it:
Since this is a sample from Oracle, I am working under the assumption that I am not running the program correctly, but I don't know what I'm doing wrong. Does anyone have any idea what I could be doing wrong?
GridBagLayoutDemo.java is declared to be in the package layout, but you placed it in the default package (no subdirectory). So either remove the package statement, or move the file in a directory called layout and then call javac layout/GridBagLayoutDemo.java && java layout.GridBagLayoutDemo.
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
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.
I've found several instructions on how to import user-built .class and .jar files to JPype, but I seem to be having a lot of trouble getting anything working at all.
What works: I can import standard java stuff and print HELLO WORLD and such.
Some of what I've tried:
I've tried adding -Djava.class.path with the path to a jar containing the relevant class files, to a directory structure containing (several folders down) the relevant .class files, as well as '-Djava.ext.dirs'. I've recompiled and re-installed with a different JVM location. The class I am attempting to instantiate is Outer, public, and has a public constructor.
I'm using Python 2.6.1 on OSX 10.6.
My current test file:
from jpype import *
startJVM(getDefaultJVMPath(), '-Djava.class.path=/Users/gestalt/Documents/msmexplorer_git/msmexplorer/MSMExplorer/build/classes')
java.lang.System.out.println("hello world")
msmexplorer = JPackage('org.joofee.meh.msmexplorer')
T = msmexplorer.MSMExplorer()
shutdownJVM()
If I use JClass I always get ClassNotFound exceptions from JPype; if I use JPackage I get Package not callable errors. Basically, JPype can't find my stuff.
Thanks so much!
EDIT (possibly helpful debugging stuff...):
Is there a straightforward way to print which third party java classes are available/imported?
Package not callable errors are referenced in this link) it would seem you need to make sure the java class file is accessible from the working directory. I am not sure how the jvm classpath comes into play, I would have thought how you did it would work.
You could also try loading the org package and then getting to the other packages through that one as the link I shared shows:
msmexplorer = JPackage('org').joofee.meh.msmexplorer
T = msmexplorer.MSMExplorer()