I have created a java source file in Source folder and also created a folder named classes which is supposed to contain my class files .
javac -d classes Source/TestMyAnnotation.java
puts my files in the directory structure classes/Source/...
Now I want to run that compiled classes but
java -cp classes/Sources TestMyAnnotation
throwing NoClassDefFoundError
Where am I doing wrong? How to do it in a correct way?
Sources is not a package folder; it's just the directory that holds your java source, so you don't need to put it on your classpath. If you take a look inside your classes directory after you have compiled your java source, you will see a file TestMyAnnotation.class - there's no Sources directory underneath it, so you don't specify it on the classpath.
You will be able to run your class like this:
java -cp classes TestMyAnnotation
You can find more information on how all this works on Oracle's Managing Source and Class Files Page
Related
I have just shifted back from an IDE to Notepad to write a Java program. The program is using 20 JARs. I compiled successfully. When I decided to run the Java class file using
java -cp ".\\*" MyProgram
it was giving the standard error "Couldn't find or load main class....".
I was confused because when I used to run the java command with all files in an existing folder, it would just get those JARs as the current folder is already in the classpath. As the program is running from the current folder, I tried using -cp "." to include it explicitly in the classpath but that didn't work either.
Finally I was able to run the program with this command:
java -cp ".\\*;." MyProgram.java
I am asking this question to understand the actual logic behind Java's classpath.
Correct me if I am wrong, but I think that the JAR is just a standard archive in which all the packages are encapsulated in respective folders. If all the JARs are in my current folder including my main class file then why can't I run it with:
java -cp "." MyProgram
or simply:
java MyProgram
If the problem is with the multiple JAR files to include and that's why we used ".\\*" to include all the JARs in the classpath, then why do we have to explicitly include the current folder again in the classpath using:
java ".\\*;." MyProgram
To include all jar required to run your program in command prompt use wildcard *:
java -classpath E:\lib\* HelloWorld
You are using "." that defines current directory and "./*" defines all files in current directory.
The class path is a list of jar files and directories containing the classes and resources of your program. Mentioning a jar file adds its contents to the class path.
"./*" will get you only the jar files in the current directory, "." adds the current directory to the class path. This allows to access all classes (and the jar files as raw file resources but not its contents, i.e. the classes contained in them).
If you need both in the class path, you have to specify both.
You've answered your own question, sort of.
. means that it will look for .class files in the current directory.
JARs act just like a directory. So to have the abc.jar "directory" you would specify abc.jar in your classpath.
If you need both the .class files present in the current directory, and the .class files packaged into JARs found in the current directory, you would have the following classpath: -cp ".:*.jar
All the answers here are telling you to use the wildcard without extension (* or ./*) but this is a bad practice, you don't want Java to go look into irrelevant files, so specify the extension: *.jar.
"." means current directory not files in the directory
"./*" means all files in current directory.
So you want to use all jars in current directory so 2nd will work
I use cmd to compile my java applications, but when I use package to pack all the files, if I try to compile them in the working directory, even if I use full path of the file, that won't work. But when I go to the parent directory, the same command works. And only works in parent directory, children directories or other directories also won't work. Can somebody tell me why? or is there any solution that make javac work in the working directory, because I use Sublime Text, its builder configs and binds the working directory.
Read https://docs.oracle.com/javase/tutorial/java/package/managingfiles.html to understand how Java source files should be organized. Espcially,
... put the source file in a directory whose name reflects the name of the
package to which the type belong...
By default the source code for my.pkg.MyClass must reside in current_directory/my/pkg/MyClass.java. You can use other than current directory with javac option -sourcepath.
For example you have two classes in two different packages packagea and packageb laying in the parent directory.
And class names are ClassA.java and ClassB.java respectively, and you have packaged your classes in these packages then you have
to use javac command in parent directory like this:
javac packagea\ClassA.java packageb\ClassB.java
Your directory structure will be like this:
Parent_directory
|
|--packagea->ClassA.java
|--packageb->ClassB.java
Otherwise, you can use any build tool like ant or maven to compile
your code. You have to just run build.xml file and your all files will
be compiled.
I have a Java project with 5 packages and 30 classes. I want to test this project on a different computer, but I can't install any sotware on that computer so I can't use things like Maven, Eclipse etc. Is there a way I can execute the program on that computer?
What I tried to do, is to compile the project using Eclipse on my computer, then went to the other computer and tried to execute the project main class via the folder that the main class .class file is at.
I.E., say that the main class name is Hello in package Greetings and Hello.class is at folder named folder. So I opened the command line window at folder and typed the command:
java Greetings.Hello
That didn't work....
Edit: After doing this I got the message: Error: Could not find or load main class Greetings.Hello
If the package name is Greetings and you want to run Hello.class
Hello class must have main method.
Hello.class must in folder name Greetings (package name).
Execute java Greetings.Hello from the one level above of Greetings folder
It seems to me Hello.class is not inside of Greetings folder
If javac is installed on the system you can directly compile on the system. you can compile even large projects including many packages with choosing different options provided by javac.
The javac tool reads class and interface definitions, written in the Java programming language, and compiles them into bytecode class files. It can also process annotations in Java source files and classes.
There are two ways to pass source code file names to javac:
For a small number of source files, simply list the file names on the command line.
For a large number of source files, list the file names in a file, separated by blanks or line breaks. Then use the list file name on the javac command line, preceded by an # character.
Source code file names must have .java suffixes, class file names must have .class suffixes, and both source and class files must have root names that identify the class. For example, a class called MyClass would be written in a source file called MyClass.java and compiled into a bytecode class file called MyClass.class.
Inner class definitions produce additional class files. These class files have names combining the inner and outer class names, such as MyClass$MyInnerClass.class.
You should arrange source files in a directory tree that reflects their package tree. For example, if you keep all your source files in C:\workspace, the source code for com.mysoft.mypack.MyClass should be in C:\workspace\com\mysoft\mypack\MyClass.java.
By default, the compiler puts each class file in the same directory as its source file. You can specify a separate destination directory with -d source
Given that you have Eclipse and you ran the code in Eclipse: the quickest way is to use Eclipse and export it to executable JAR.
If you have Run Configuration (e.g. named Hello) that you use for running the code:
Menu -> Export -> Runnable JAR file
Launch Configuration: Hello
Select export destination: (e.g. C:\tmp\Hello.jar)
Set Extract required libraries into generated JAR
Click finish.
This will create Hello.jar file you can execute typing in:
java -jar Hello.jar
I am a newbie in java I Want to know that what is the default directory for packages in java ? I Mean if i compile a java file which contains a package statement,and i compile it without using -d option in javac command,then where will be the package created ? eg.
package test;
class Test{}
and compile it using javac Test.java
then where will be the package created?
Thanks
If you don't specify -d, the class file will be created in the same directory as the source file.
That's fine if you're already storing your source in a directory structure matching your package structure (and if you're happy for your source and class files to live in the same place) but if your source structure doesn't match your package structure, you'll basically end up with class files in locations where they can't sensibly be used.
Personally for anything other than quick throwaway (usually Stack Overflow :) code I would make the following suggestions:
Avoid using the default package
Keep your source code in a directory structure (e.g. with a root of src) matching package structure
Generate class files into a separate directory structure (e.g. with a root of bin or out or classes)
(Sorry, misread the question to start with.)
-d option in javac command is use to specify where to generate the class file,if you don't specify it,then the .class file will be created in the same directory where your .java file is present.
There is no directory created when you do not specify the package!
all the .class files will be created directly in the output folder
public class A{}
if you compile this to output folder ,
output/a.class is created
With reference to this post
Receiving "wrong name" NoClassDefFoundError when executing a Java program from the command-line
I did not understand how to solve the problem
Actually in my java source code there' s line :
package es_2011;
when I compile the program through JCreator everything works perfectly.
It creates a folder named es_2011 where to put .class files.
Also the executing operation goes smoothly, the program runs ok.
Now I'd like to use the command line only.
So I placed my java file in the directory where javac.exe is but whenever I try to compile I get the same error
The command I use is: javac ProgAudioJ.java
The path (where javac.exe is ) is : C:\Program files\Java\jdk1.6.0_22\bin
Is someone willing to help me understand in terms of exactly tell me what I have to do?
thanks very much...MAX
The setup used for the looks like this (under windows)
C:\classDir -> is the project
C:\classDir\testpackage -> is the only package used (the package "testpackage")
C:\classDir\testpackage\Main.class -> is the class with the main method inside (important: it is the .class and not .java)
The Main.class looks like following:
package testpackage;
public class Main {
public static void main(String[] args) {
System.out.println("Program started! ;-)");
}
}
go with your command prompt to:
c:\classDir> java testpackage.Main
the result:
Program started! ;-)
According to your problems that it starts in your IDE but not from the console:
- checked if you realy use the path to the .class files?
- with the console go to the directory of you .class files, not the project (e.g. in Eclipse it is the bin directory
- enter the full qualified class name (including packages seperated by . -> e.g. testpackage.Main
More infos can be found under:
http://www.oracle.com/technetwork/java/compile-136656.html
Hope it helped
MAX, if the class defines that it's inside the package es_2011, then it should be in a folder with the same name.
So in your case, put the ProgAudioJ.java in the folder es_2011 and then run
javac es_2011\ProgAudioJ.java
latter to run it, you need the command
java es_2011.ProgAudioJ
You should add javac.exe in your path .Edit your path variable and append path to jdk's bin
then put java file in a dir named es_2011 , as the package declaration is es_2011 then compile
c:\es_2011\javac YourJava.java
and now go back to C:
c:\java es_2001.Yourjava
After reading you other Post: "Receiving "wrong name" NoClassDefFoundError when executing a Java program from the command-line" I guess you go to the directory es_2011 where your ProgAudioJ.class file is located and run
java ProgAudioJ
from that folder.
instaend you have to go to the folder above (cd ..) and run
java es_2011.ProgAudioJ
Each package in Java corresponds to a folder on the filesystem. So a package declaration such as com.stackoverflow would mean that the source classes need to be in a folder ./com/stackoverflow. Typically the whole project would have a separate src folder containing com/stackoverflow.
When you compile the Java classes you DO NOT need to put source files in the same directory as javac.exe, you do however need to make sure that javac.exe is in your operating systems PATH variable. This tells the operating system where it should look for executable files when a command is run, on a *nix machine this would usually be /usr/bin or just /bin but on Windows machine the executables normally live within the applications own directories, that is C:\Program Files\something. Assuming that you've installed JDK correctly, the javac.exe should already be in the PATH you can check this by opening the command line and just running javac (just like that). If you get some output then all is well, the system knows where to find javac.exe.
Next you will need to go to your project folder and type javac -d . src/com/stackoverflow/MainSO.java notice that is run from the project folder. This will create a folder called com in your project root and put the compiled classes in com/stackoverflow. The -d flag tells javac where to put the compiled classes, if you leave that out, the compiled classes will be where the sources are.
Then when you want to run the classes you type java com.stackoverflow.MainSO (no .class). Crucially this command will need to be ran in the directory that contains the root of the class hierarchy (that is the com folder containing the compiled classes). You can specify other places for java to look for the classes by providing a classpath to the java command with the -cp flag. By default the classpath will contain the directory the java command was ran in. Should your project have dependencies external .jar files for example you will need to provide every single one of them (with their full filepath) in the classpath (this goes for the compiler as well). The IDEs do this automatically for you.
Hope that helps.