Just today I noticed that I can run java in eclipse with no problems but when I try to run it in the command prompt, I get "cannot find or load main class." The command prompt actually compiles all right, and it outputs a .class file, but then it displays the error msg when trying to execute. (Also, I was able to run java in the cmd a couple weeks ago.)
/* work area for practice
*
*/
package Scrap;
public class experimentational {
public static void main (String [] args) {
System.out.println("welcome to java!");
}
}
Found the answer: (i'm using different code but it is still relevant to this problem)
java -cp . hiThere
output: "Hi there"
I know this is classpath but don't know why it works or what the period does for it. Anyone have an idea?
Use:
javac Scrap/experimentational.java
followed by:
java Scrap.experimentational
try java -cp . [your main class].
Did you install a JDK on the machine outside of Eclipse? If you did, then make sure you set your path variables correctly. Open a command prompt (assuming windows) and type java -version
If the JDK was installed properly and path variables were set properly it should tell you the version of Java that was installed. If it tells you that 'java' is not recognized as a command that you do not have a JDK installed, or it was not installed properly.
The reason your program runs in Eclipse is that Eclipse for Java has its own internal JDK and JVM.
Your other option is to set up your path variables to point to Eclispe's internal JDK.
If you were able to run it from a command prompt previously then most likely your class path was altered. Is this a machine at work? Some companies have SMS tasks that come through periodically and restore default system settings (including path variables) to corporate defaults.
Maybe java and javac isn't in your OS path.
If you are using Microsoft Windows in cmd type path and then enter.
If jdk or jre isn't in path you need to put them to it
I had a similar issue when I copy pasted code into an editor. I removed the package declaration on line 1 and it ran then. So I'd investigate above comments on packages, after trying first to remove the package line.
Related
I am trying to change my java version because of compiler errors when running mvn install via the windows command prompt.
I changed the JAVA_HOME variable and made sure that it is referenced in the PATH variable (##EDIT##: had been done like this %JAVA_HOME%\bin;%PATH%;).
When I open the command prompt in the folder where my pom.exe is located (using the Windows 7 'Open command window here' shortcut) and type java -version the unchanged java version is displayed.
I made sure to close all instances of command prompts before starting a new one.
Strangely I discovered that when starting the command prompt via the Run dialog in the start menu (by typing cmd) the result of java -version is the desired version.
You need to modify path variable as well as below:
PATH=%JAVA_HOME%/bin;%PATH%
Post that make sure you open a new command prompt and rerun maven command.
When using the 'Open command window here' shortcut make sure to close and open the respective explorer window. When starting the command prompt in this way Windows uses cached environment variables and does therefore not retrieve the current version of java.
Took me a while to figure out because it was too surprising to expect this behavior. Before I was searching on google and stackoverflow.com without any results. Hope this saves someone the trouble.
In my case worked the following: after editing the environment variables, and checking by command line java -version and javac -version, javac was updated but not java, so you have to do it by command line also
set path=C:\Program Files\Java\jdk1.8.0_181\bin
Remove the existing JRE setups..
Install the one that you need to install.
Hope you have added it in the environment variable and path via settings... Test it, it should work!.
The same thing happened to me long ago, It was pointing to the older JRE, got stuck, so removed the existing JDKs and installed a fresh copy. It worked.
I too faced this problem where I want to change the java version in command prompt but failed. But finally I succeeded doing the below steps. First I'll show the failed attempt, followed by the actual success step so you will know the difference.
Failed Step:
1. Win + R
2. Type cmd and hit enter
3. Type java -version (Just to check if the version is the old one which we need to change)
4. Now try changing the path/classpath using set path=/classpath=
5. Now again type java -version(This will still show the old java version but not the new version which we set)
Success Step:
1. Win + R
2. Type open command window here and hit enter
3. Type java -version (Just to check if the version is the old one which we need to change)
4. Now try changing the path/classpath using set path=/classpath=
5. Now again type java -version and voila I see the changed java version here
Thanks!
I had the same problem too. After setting the JAVA_HOME, i couldn't see the new value in command prompt even though I started a new command prompt.
Strangely, it only occured when opening the command prompt from the Windows Explorer.
I faced this issue too. I changed the JAVA_HOME in the environment variable and then when I opened cmd and typed java -version, I've seen older version. Then, I deleted javapath file in C:/Program Files/Common Files/Oracle/Java. My issue has been fixed in this way.
I'm getting started with java development. So, I installed JRE and JDK in my computer.
Then, I created a simple Example.java file and saved it in my Desktop.
In the prompt, I executed
javac Example.java
and it worked ok. A .class file has been created in my Desktop.
Then, I tried to run the class, executing this:
java Example
and I got an error in a window alert, with this message:
Java Installation Not Completed
Unable to install Java
There are error in the command line switches: "Example";.
Check that the commands are valid and try again
Then, for testing, I executed both commands:
javac -version and
java -version. Both are installed in my computer.
What am I doing wrong?
I am running Windows 8 and have already set my environment variables.
Example.java:
public class Example {
public static void main(String args[]) {
System.out.println("Finally Java");
}
}
Try to remove installation again, look for all leftovers and remove them manually, if you changed the directory you installed java to, remove environment variables as well and set them again. You should also make registry cleanup: https://java.com/en/download/help/manual_regedit.xml Make installation through offline installer.
I have done a lot of researching on this concept but I can't seem to run a java program on the command prompt. Let's say we had a simple program like this:
public class Hello_World {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}
On the command prompt I tried:
javac Hello_World.java
But I get:
'javac' is not recognized as an internal or external command, operable program or batch file
So I compiled it on BlueJ and then did this:
java Hello_World.java
But it said "cannot load or find main class Hello_World"!
I am currently using Windows 7, and made the programs on Notepad++ and BlueJ (to compile).
Any suggestions? Thanks!
This explains in detail what you have to do to set class path. Primarily you need to set your environment variables so that your shell finds the right directory containing javac to compile your program
javac' is not recognized ..
comes when you haven't point your java bin directory to your path environment variable. Because bin directory is the place where javac.exe exist.
To do it.
1) right click on mycomputer property
2) go to Advance system settings.
3) go to environment variable.
4) In system variable click on path
5) go to edit mode and provide your path to java bin directory.
in my case it is C:\Program Files\Java\jdk1.7.0_01\bin;
'javac' is not recognized as an internal...
means OS does not know where javac program is located. Either add it to PATH or run explicitly
my\path\to\file\javac Hello_World.java
Compiling will convert *.java to *.class
Hello_World.class file should be located according to it's package directive. Since you have no one, in your case it should be located in the same directory you will run java.
To run your class specify it's name not file name
java Hello_world
looking for the class is essential part of launching and occurs by rules.
I am trying to run my java program from command line.
I read an article about setting up classpath, but I get an error of javac is
not recognized as internal or external command. What should I do? (I dont want to set a permanent CLASSPATH)
This is what I have done in my command line
D:\user> set path=%path%;C:\Program Files\Java\1.7.0_07\bin
D:\user> cd testing
D:\user\testing> javac firstProgram.java
'javac' is not recognized as an internal or external command,
operable program or batch file.
Thank you
Assuming that the PATH is correct1, the most likely cause is that you have a JRE installation ... and a JRE doesn't include a java compiler. You need a JDK installation if you want to compile from the command line.
(You can confirm this by looking in the C:\Program Files\Java\1.7.0_07\bin directory to see if it contains a javac.exe file. A JRE won't ...)
Where can I find the Java compiler to download..
You need to download one of the JDK installers; see http://www.oracle.com/technetwork/java/javase/downloads/index.html
1 - I don't think quotes are required in a PATH variable on Windows. At least that's what various examples that Google found for me seem to imply. But I've never really understood the logic behind quoting in Windows ...
Its an issue related to Program Files.
First make sure that your JDK Folder is installed in Program Files or Program Files(x86) or any other folder.
Then you should use the path of bin folder in " ". Because command prompt does break the string at space. When you will write it in " " then it will take is as a whole String.
You try these commands
set path=%path%;"C:\Program Files\Java\1.7.0_07\bin"
or
set path=%path%;"C:\Program Files(x86)\Java\1.7.0_07\bin"
It might help you to get out of this.
Better do it in Environmental variable and check it!
try below command is recognized from command prompt
C:\Program Files\Java\1.7.0_07\bin\javac ab.java
This is just to verify your javac
Here's how you can set the path temporary, meaning if you close and reopen "command prompt" you will have to set the path again.
Assuming the path is C:\Program Files\Java\jdk1.6.0\bin
TYPE IN C:\Program Files\Java\jdk1.6.0\bin AND HIT ENTER
that's it.
The commands D:\user> set path=%path%;C:\Program Files\Java\1.7.0_07\bin works well for me
Adding few more information to this:
Please check the version of JDK and JRE installed on your computer. Recently I faced the same problem even after setting the PATH. It gives the error "javac - command is not recognised"
Solution is there must be similar versions of JDK as well as JRE
E.g.: JDK 1.7.75 along with JRE 1.7.75
I dad left Java since so long as a result now it happens that sometimes I forget the simple things and used to behave like a Stupid.
To run a Simple Java program say "Hello World" written in Notepad what do I have to Do?
I know the commands javac "Filename.java" and java "Filename" respectively to run it from the Command prompt.
But When I try to do that I got this message:
"javac is not recognized as an internal or external command, operable program or batch file."
and I could not Complie the file.
I hava little idea that we need to do some stuffs like setting the classpath or perhaps the path evnironment variables but it was exactly that I don't remember.
Can anybody please help me?
Thanks,
david
Add a JAVA_HOME env variable to point to the jdk installation directory
To your PATH env variable, add %JAVA_HOME%\bin
Add a CLASSPATH env variable to point to %JAVA_HOME%\lib.
remember to open a new console window and try running javac and java - everything should be fine now.
1) create JAVA_HOME environmental variable set value to java home directory
e.g. c:\program files\java\jdk1.5;
1) set PATH in environmental variable to your java bin directory
e.g. %JAVA_HOME%\bin
and to check classpath is set correctly run javac command on cmd
and this link will help to create and run simple java application
java tutorial
this might be usefull budddy
http://www.apl.jhu.edu/~hall/java/beginner/settingup.html
You need the JDK to be able to run javac.
I suggest you first start coding in eclipse, it provides all the environment set up for you. Once you get good with coding, you can try command prompt compiling and running. That way, you will be confident with language first and then go into the nitty-gritties of the environment and set up.
Its better to use any java IDE either eclipse or netBeans Download Link
But in case if you like to go through Command prompt method, then u need to set the paths. (These are the variables for your OS, that used to know where your commands e.g. java or javac etc are located). Hope from other answers you set the paths.
Good luck