This is probably a stupid question, but how do I run a class file on windows 7? I usually create my own .java files and then use a basic IDE (with JDK6) to compile it to a class and run it automatically. My professor gave a .class file that we are supposed to play with extensively but I have no idea how to to run it here. Note that I cannot run it by typing:
java classname.class
because it contains gui stuff especially buttons and such. If I do the above I get the following error:
java.lang.NoClassDefFoundError: Test1/2/class
Caused by: java.lang.ClassNotFoundException: Test1.2.class
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
Could not find the main class: Test1.2.class. Program will exit.
Exception in thread "main"
Any help would be highly appreciated. Thanks.
When you run it, don't include the .class suffix:
java classname
In addition to the above, it should also make no odds what your O/S is. Java compiles to byte code, which is interpreted by your JVM. You clearly have one installed since you got the java error you have pasted above.
Like codeka said, you need to type java ClassName at the command line, and if the class has a main method, it will be run.
Java compiles each class that is defined in a particular source file into its own class (byte code) file. For example, Apple.class, Banana.class, and Cherry.class might get output after compiling Apple.java, if they are all defined there. So the actual name of the class in source will match the name of the file, minus the extension.
Now, let's say that someone accidentally (or intentionally, from the sound of it) renamed the class file. You have a file called WrongName.java, and you type java WrongName. Note that the output will begin with the line:
Exception in thread "main" java.lang.NoClassDefFoundError: WrongName (wrong name: RightName)
Where RightName is what it should be. At that point you would rename your file to RightName.class, type java RightName, and hopefully it will run. And if the name has a slash, then whatever precedes the slash is the name of the package. Let's say it's PackageName/RightName. First you need to create a directory called PackageName, and put RightName.class inside of it. Then, go one level up in your directories, and type java PackageName.RightName.
Note the different kinds of exceptions: ClassNotFoundException basically means that the class file was not found. NoClassDefFoundError means that the class definition was not found. If the class does not have a main method and you try to run it as a program, you will get NoSuchMethodError: main.
Related
I've written a program to read in data from a text file and do some simple calculations, then print out those calculations. That part works great.
Afterward, I added in some code to do a t-test, using the TTest class (org.apache.commons.math3.stat.inference.TTest). So, I downloaded commons-math3-3.6.jar from the Apache Commons download page and put the JAR file in the same folder as the rest of my Java code for this program.
I use the following command in Windows to compile, which works fine:
javac -cp ./commons-math3-3.6.jar ./FootballTeam.java ./Main.java
But I can't figure out how to correctly run the program. I've tried this:
java Main
which executes everything up to the t-test perfectly, and then gives the expected error:
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/math3/stat/inference/TTest
at Main.main(Main.java:32)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.math3.stat.inference.TTest
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 1 more
I've also tried this:
java -cp commons-math3-3.6.jar Main
which gives me this:
Error: Could not find or load main class Main
I cannot for the life of me figure out how to properly set the classpath here. Can someone provide me some assistance? Thank you!
The Main class cannot be found because the current directory (.) is not on your classpath.
To add it, on Windows:
java -cp ".;commons-math3-3.6.jar" Main
On *n?x:
java -cp ".:commons-math3-3.6.jar" Main
I have a java application where main class is dependent with some other classes. I can run the application using an IDE well. But when I want to run the application from command line by locating to the main class's class file using java mainClass, it gives me the following error [the main class name is mainClass]:
Exception in thread "main" java.lang.NoClassDefFoundError: mainClass(wrong name: mainfolder/mainClass)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)
Can anybody suggest me how can I run my application without using any IDE?
Uou need to indicate the fully qualified name. For example if MainClass is under package com.example, you should execute java com.example.MainClass
You can check more here.
From documentation:
By default, the first non-option argument is the name of the class to
be invoked. A fully-qualified class name should be used. If the -jar
option is specified, the first non-option argume nt is the name of a
JAR archive containing class and resource f iles for the application,
with the startup class indicated by the Main-Class manifest header.
The Java runtime searches for the startup class, and other classes
used, in three sets of locations: the bootstrap class path, the
installed extensions, and the user class path.
Try mainfolder.mainclass instead of mainfolder/Mainclass. Also, the mainfolder is the package.
Make sure you put all needed jars in the classpath with -cp.
With or without IDEs, java application can always start by
java -cp classpath EntryClass
If you run the application with IDEs, the IDE you using prepares the classpath for you. If you run without the IDEs, you should prepare the whole classpath yourself.
The EntryClass is also found through the classpath.
Please refer to java - the Java application launcher for details.
Let say you are runngin your java program from /home/flyleaf/app/
This would be the command you need:
javac -classpath /home/flyleaf/app/jar1.jar:/home/flyleaf/app/jar1.jar:/home/flyleaf/app/ com/app/your/mail/class/Main.java
You need to add to the classpath the jar files you need and the path where you got your program
Ok! Got the output after executing the java command over the main class's class file with package.classname from outside the folder that contains the class files!
Besides the jar file is also working after locating the jar file and by executing this command java -jar jarname.jar!
Thanks everybody!
I'm trying to run a Java app from the cmd, and I'm getting the following Errors:
Exception in thread "main" java.lang.NoClassDefFoundError: Main
Caused by: java.lang.ClassNotFoundException: Main
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: Main. Program will exit.
In the dir you can find:
Directory of C:\Java
AVLNode.java
AVLTree.java
Comparator.java
HashTable.java
input1.dat
input2.dat
Main.java
StringComparator.java
and I'm Running:
java Main input1.dat input2.dat output1.dat
I have Main.Java in the folder and I have:
public static void main(String[] args) method on the Main.Java (and some more functions)
I already read the answers about this problem here but I think I did everything alright :( so what can be the problem?
Check whether you have Main.class file in your current directory or not. If it is already there, check your path variable in you system environment variables. It should point to JAVA_HOME\bin.
as stated in another answer check if Main.class is present in current directory
also try java -cp . Main arg1 arg2
above line sets classpath to current directory
First make sure that you have compiled your code.
You should be in the directory that contains the Main.class (If you are using eclipse IDE it will be bin/).
If your Main class is in a package you should run your command from the directory that contains the package and your command will be java [package name].Main [arguments]
If you want to run your command from anywhere you can use the -cp option like the following :
java -cp [classpath] [package name].Main [arguments]
with classpath : path to the directory containing the .class until right before the package
In addition to what the others suggested, check to see if you have any package statements in Main. If so, you must include it when starting the program.
For example, if you have:
package mypackage;
public class Main
{
public static void main (String[] affhf)
{
}
}
then you must start your program by calling:
java mypackage.Main input1.dat input2.dat output1.dat
This might slip by the compilation process in some situations...
Looks like you haven't compiled your code. Try the following:
cd Java
javac Main.java
This should create the .class files in the Java directory. Then, without changing the directory, try:
java Main input1.dat input2.dat output1.dat
I have a java file which uses jfreechart libraries, uses a text file from local drive and displays graph. Runs fine with eclipse. However, I want to run this from cmd prompt, other simple Java files are able to run successfully via cmd prmnt but not able to run this file.
PS: MyTool.java is able to compile without errors and class file is created, but not able to run.
1) This is how I am compiling it in cmd prompt: (gives 0 errors)
C:\Documents and Settings\hello.maga\workspace\MyTool\lib>javac -cp "gnujaxp.
jar;iText-2.1.5.jar;jcommon-1.0.16.jar;jfreechart-1.0.13.jar;jfreechart-1.0.13-e
xperimental.jar;jfreechart-1.0.13.jar;junit.jar;servlet.jar;swtgraphics2d.jar" MyTool.java
2) This is how I am running it:
C:\Documents and Settings\hello.maga\workspace\MyTool\lib>java -cp "gnujaxp.j
ar;iText-2.1.5.jar;jcommon-1.0.16.jar;jfreechart-1.0.13.jar;jfreechart-1.0.13-ex
perimental.jar;jfreechart-1.0.13.jar;junit.jar;servlet.jar;swtgraphics2d.jar" MyTool
Error for second command:
Exception in thread "main" java.lang.NoClassDefFoundError: MyTool
Caused by: java.lang.ClassNotFoundException: MyTool
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: MyTool. Program will exit.
What I don't understand is, if there are any errors, then it should not compile in first place, can someone educate me. Thank you very much.
You need to include "." in the classpath, like so:
java -cp ".;gnujaxp.jar;iText-2.1.5.jar;jcommon-1.0.16.jar;jfreechart-1.0.13.jar;jfreechart-1.0.13-experimental.jar;jfreechart-1.0.13.jar;junit.jar;servlet.jar;swtgraphics2d.jar"
From "Setting the class path": "The class path tells SDK tools and applications where to find third-party and user-defined classes -- that is, classes that are not Java extensions or part of the Java platform. The class path needs to find any classes you've compiled with the javac compiler -- its default is the current directory to conveniently enable those classes to be found."
However if you set the classpath yourself, the default no longer applies, and you're expecting it to load classes from the current directory. You'll have to add it manually, like by adding "." to the class path as Ed Staub recommended.
When compiling, your class wasn't needed on the class path, so to speak, since it's what was being compiled. You only needed all the other classes (in the jar files) on the class path for that. That's why you're able to compile but not run, even though you used an identical class path for both operations.
So i need to write a program that accesses and modifies an SQLite DB for a school program and am looking at the basics firstly. Now, I am looking at this to get me started: link text. The problem is that when i compile Test.java (The example code on the website) and then run the command:
java -cp .:sqlitejdbc-v056.jar Test
like it tells me to, i get the following error:
Exception in thread "main" java.lang.NoClassDefFoundError: Test
Caused by: java.lang.ClassNotFoundException: Test
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
Could not find the main class: Test. Program will exit.
Test.java, Test.class and sqlitejdbc-v056.jar are all in the same folder so they should find each other. Does anybody have an idea about what i am doing wrong?
According to the java.lang.NoClassDefFoundError: Test, the Test class cannot be found in the CLASSPATH. But you wrote that Test.class is available in the current directory so I'm gonna guess something. Actually, I think that you are not using the right CLASSPATH separator character (which is platform dependent) and thus not building correctly the CLASSPATH. On Windows, you should use ; instead of :. If this happens to be the case, you should try this:
java -cp .;sqlitejdbc-v056.jar Test
If you are on a unix-like platform, forget this answer, the problem is elsewhere.
As the exception message is saying, the problem is that it cannot find the class Test. So the problem is not finding SQLite, but finding your Test class.
Just a guess, but I am wondering if there is an issue with how you compiled. In the Test.java, does the class belong to a package? If so, you need to compile it using the -d flag so that it gets put in the appropriate sub-directory.