I have access to amazon cloud service ec2, linux instance. I created vi first.java file with this content:
class first {
public static void main(String[] args) {
System.out.println("abc");
}
}
I want to compile the file using:
[root#ip-21-24-273-243 ec2-user]# javac first.java
bash: javac: command not found
Command not found? I do:
[root#ip-21-24-273-243 ec2-user]# java -version
java version "1.6.0_24"
OpenJDK Runtime Environment (IcedTea6 1.11.9) (amazon-57.1.11.9.52.amzn1-x86_64)
OpenJDK 64-Bit Server VM (build 20.0-b12, mixed mode)
So java is installed. How can I run a simple app?
[root#ip-21-24-273-243 ec2-user]# yum install java
Loaded plugins: priorities, security, update-motd, upgrade-helper
amzn-main | 2.1 kB 00:00
amzn-updates | 2.3 kB 00:00
Setting up Install Process
Package 1:java-1.6.0-openjdk-1.6.0.0-57.1.11.9.52.amzn1.x86_64 already installed and latest version
Nothing to do
You need to install java-1.6.0-openjdk-devel:
yum install java-devel
As already mentioned, to compile a Java program you need JDK. Here you may find some useful information on how to install JDK on a Fedora AMI: Compiling and running Java app
However, you should notice that you don't need to compile on your ec2 instance. You can compile your Java program on your home desktop/laptop computer and transfer compiled .class (packed in a .jar) files to the instance, and run them there - the already installed JRE should be enough to run the program. That is a preferable approach, cause you can comfortably use Eclipse for development. Develop, test on your local machine, deploy on ec2.
There's a few steps to do:
Make sure you have a Java compiler installed. You can find this out by entering $javac into your console and seeing what comes up. If it's not installed, follow the previously mentioned instructions to $yum install java-devel
Create your script (first.java)
Compile it using $javac first.java
You will now have first.java and first.class... execute it by executing $java first
"[Java] Runtime Environment" or "JRE" for short doesn't include the developer tools, one of them being the Java Compiler. You need to install Java Development Kit or "JDK" for short. The exact mechanism depends on which AMI you used to build your instance.
In order to create and run a basic java program on Amazon EC2, you would require to do following:
When you login to EC2 instance, check whether JDKis installed or not, fire javac -version for it.
If you do not have JDK installed you would see something like this:
Install JDK, fire sudo rpm -i jdk-8u11-linux-x64.rpm
Having java installed, you can create a file file.java using any editor.
Edit the file and save.
Compile java File, javac file.java
Run it, java file
Related
I am running IntelliJ IDEA 2017.1.6 Pro on a Linux (Ubuntu) machine and, it will not let me select an SDK for any Java project.
Whenever I start up the program and go to "Create a New Project" Java has no SDKs available. If go to new and try to specify where my JDKs are installed (I have a few) it always fails with the same error:
I've tried specifying the locations:
/usr/lib/jvm/
/usr/lib/jvm/java-11-openjdk-amd64/
/usr/lib/jvm/java-8-openjdk-amd64/
/usr/lib/jvm/openjdk-11/
/usr/lib/jvm/jdk-14.0.2/
/usr/lib/jvm/default-java
/usr/lib/jvm/java-1.11.0-openjdk-amd64
/usr/lib/jvm/java-1.8.0-openjdk-amd64
(these last three are all just symlinks)
I know I have a JDK installed for my default Java version. I can compile and run code via command line:
justin#stephanie:~/temp$ ls
HelloWorld.java
justin#stephanie:~/temp$ javac HelloWorld.java
justin#stephanie:~/temp$ ls
HelloWorld.class HelloWorld.java
justin#stephanie:~/temp$ java HelloWorld
Hello, World!
The output of readlink -f $(which java) is /usr/lib/jvm/java-11-openjdk-amd64/bin/java (same location for javac exectuable).
Everything I've looked at online suggest that I should just be able to select /usr/lib/jvm/java-11-openjdk-amd64 as my Java SDK but it is failing. I feel like I must be misunderstanding something essential here as I don't know why this isn't working.
Any help would be useful, I've never used IntelliJ before (I've always been an Eclipse user) and it is very frustrating I can't even create a project in it after a couple hours of trying to mess around with it.
1. Please try first with a newer version of IntelliJ, preferably the most current one (currently this is 2020.2)
2. I had the same problem (with version 2020.2 on my Kubuntu system) and fixed it by simply downloading and installing the SDK via IntelliJ.
The /usr directory is mounted at /var/run/host.
You should find your jdk under /var/run/host/usr/lib/jvm.
I'm having trouble removing Java 9 from my macOS Sierra system.
I accidentally installed Java 9, instead of Java 8, so now all my Eclipse projects give me these warnings: Build path specifies execution environment JavaSE-1.8. There are no JREs installed in the workspace that are strictly compatible with this environment.
I have used the following guide, but it did not work. Here is my command output when running java -version from the command line:
java version "9"
Java(TM) SE Runtime Environment (build 9+181)
Java HotSpot(TM) 64-Bit Server VM (build 9+181, mixed mode)
for macOS high sierra removing java 9:
delete the java folder you find in the dir shown to you after executing:
/usr/libexec/java_home -V
use "Go to" in finder and copy and paste the dir to get there
There are two commands which are very simple and useful. If you want to keep multiple versions simply set JAVA_HOME to version you want to use.
export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_(version you want to use).jdk/Contents/Home
Example--> export JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_161.jdk/Contents/Home
Else in addition to above command remove/uninstall additional jdk version from your system with below command.
sudo rm -rf /Library/Java/JavaVirtualMachines/jdk-(version you want to remove).jdk/
Example --> sudo rm -rf /Library/Java/JavaVirtualMachines/jdk-9.0.4.jdk/
Please refer below github link for additional details -->
https://gist.github.com/schnell18/bcb9833f725be22f6acd01f94b486392
Thanks
On MacOS you can list what JDKs you have installed and where they are installed to with:
/usr/libexec/java_home -V
If you want to select one of the installed JDKs to be used as default, you can do:
/usr/libexec/java_home -v 1.8
Verify which is now default with java -version.
You can manually add the location of other installed JREs in Eclipse via Preferences / Java / Installed JREs , press Add, and then point it to one of the locations should with the -V option above. You can then check it to select which is default for your projects.
After viewing which Java Virtual Machines I had on my computer using the following command:
ls /Library/Java/JavaVirtualMachines
I realized no additional JDK's would appear after using the Java 8 installer (besides Java 9). When doing further research, it turns out I had installed the other version that is not a SE development kit and it was just working in web browsers, not for the terminal.
For anyone having the same issue, make sure you use the Java SE Development Kit 8.
Uninstall Oracle Java using the Terminal:
Note: To uninstall Java, you must have Administrator privileges and execute the remove command either as root or by using the sudo tool.
Remove one directory and one file (a symlink), as follows:
Click on the Finder icon located in your dock
Click on the Utilities folder
Double-click on the Terminal icon
In the Terminal window Copy and Paste the commands below:
sudo rm -fr /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin
sudo rm -fr /Library/PreferencePanes/JavaControlPanel.prefPane
sudo rm -fr ~/Library/Application\ Support/Java
Do not attempt to uninstall Java by removing the Java tools from /usr/bin. This directory is part of the system software and any changes will be reset by Apple the next time you perform an update of the OS.
Source:https://www.java.com/en/
I believe the problem is navigating to the correct directory... Once you are where you are supposed to be you can run the sudo commands to remove whichever versions of java you want to remove.
First, run the command in the terminal to determine which version of Java you are running,
java -version
then you can navigate to pesky version of java that you intend to delete by using the following command:
cd /Library/Java/JavaVirtualMachines
then once you see are in the JavaVirtualMachines path, type in ls to see what versions of Java you have installed,
ls
and finally when you know which version or versions of Java you want to uninstall:
sudo rm -rf jdk-10.0.1.jdk #or whichever version you want to delete
I know that you've asked about how to uninstall the java version. But, I think it's important how to manage your Java version in a very good way.
For me, the best way is using SDKMan, a very nice tool for managing you Development tools like Java.
Here you can learn more about it: http://sdkman.io/
You can install your Java version as follow:
$ sdk install java
You can install others tools like Scala:
$ sdk install scala 2.12.1
Uninstall your tools very easy:
$ sdk uninstall java 9
And so on. Hope this helps you in future installation of your development tools.
This question already has an answer here:
JavaFx Ensemble on Raspberry pi
(1 answer)
Closed 7 years ago.
I have downloaded the latest OS for the pi from here http://downloads.raspberrypi.org/raspbian_latest
Then i have downloaded the latest Java JDK to run my JavaFX application from http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html and selected the Hard Flat v6/v7 file.
I have transferred and unzipped the JavaJDK onto my Pi.
Now if i execute this command on my local machine, my application starts
Java -jar program_name.jar
But if i run the same command on the Pi, i get an error saying
Could not find or load main class application.Main
If i change the .jar file into a .zip, i can clearly see a directory called application, and file called Main.class
So why is my program working on my (windows 10) machine, whether i run it from eclipse or the command line, but not on the raspberry Pi?
To install the Java Runtime Environment (JRE) run the following command:
sudo apt-get install openjdk-7-jre
This installs the Java JRE (Java Runtime Environment) which will allow you to run applications written in Java.
To install the JDK run the command:
sudo apt-get install openjdk-7-jdk
This allows you to compile Java applications to bytecode.
If you want the Oracle Java VM, which is a lot faster (optimized for embedded arm CPUs) and is also a developer preview (applications maybe buggy or crash) until some time into the future. Instead of the above instructions you need to download the file called Oracle JDK 8 (with JavaFX) for ARM Early Access on the Oracle Java 8 download page.
Remember to download the Oracle Java system on your Pi, or you won't be able to install it.
To install the Oracle Java System:
sudo tar zxvf jdk-8-ea-b36e-linux-arm-hflt-*.tar.gz -C /opt
sudo update-alternatives --install "/usr/bin/java" "java" "/opt/jdk1.8.0/bin/java" 1
sudo update-alternatives for other commands if needed (e.g. javac).
java -version
Then it is all installed.
Another thing, if you have more then one Java runtime installed you have to check which version you use with the command java -version. If the output is:
java version 1.5.0 gij (GNU libgij)
Then you are using another java runtime. You can resolve the issue by running
sudo update-alternatives --config java
and choosing the OpenJDK or Oracle option.
Once again, I spent much time trying to get something to work without success.
I want to install MATLAB Compiler Runtime on my Ubuntu 13.04, where there is no MATLAB installed.
Here's what I did:
I downloaded the 64-bit Linux version R2012b(8.0) off of
http://www.mathworks.com/products/compiler/mcr/index.html?s_cid=BB.
Then, I switched into the folder and tried to install via
sudo ./install just to receive the following message:
Error: Cannot locate Java Runtime Environment (JRE).
The directory /home/konni/Downloads/MCR_R2012b_glnxa64_installer/sys/java/jre/glnx86/jre does not exist.
And, it does not exist indeed, but there exists a folder with "glnxa86" instead of "glnx86". I wouldn't just want to rename it, though.
I do have a JRE installed on my machine, btw:
java version "1.7.0_25"
OpenJDK Runtime Environment (IcedTea 2.3.10) (7u25-2.3.10-1ubuntu0.13.04.2)
OpenJDK Server VM (build 23.7-b01, mixed mode)
I have absolutely no clue what to do. The problems I found using google didn't quite help me, either...
Maybe you have an idea?
I'd greatly appreciate any help! :-)
If the only problem is finding the JRE, then the command line switch -javadir will get you done:
./install -javadir /usr/lib/jvm/java-7-openjdk-i386/jre/
I had the same problem recently when installing a software that required a 7.13 MCR on an Ubuntu 17.10.
In this
https://www.linuxquestions.org/questions/linux-newbie-8/matlab-7-5-compiled-runtime-for-64-bit-linux-installation-no-jre-error-838281/
I found that the 32 bit version installs fine, and it did, but obviously, that didn't solve my problem.
However, I found a way to do it. The trick is that the installer needs the old JRE (1.5) and will not work with JDK 8.
So the first step is to run
./MCRInstaller.bin -is:extract
this will create a directory called istemp... something, for me istemp23732345211606.
ls
jre1.5.0-linux-amd64.bin JVMNotFound.txt setup.jar Verify.jar
It is tempting to run the setup.jar directly, do try, but with Java 8, I only got the following error message:
Could not load wizard specified in /wizard.inf (104)
But perhaps it will work for you. People who get the above mentioned error with wizard.inf should look further, because the installer needs JDK 5 to run.
I chose not to use the bundled version but downloaded the JDK 5 from Oracle. The bundled version might work as well - I did not try.
You can download JDK 5 from here:
http://www.oracle.com/technetwork/java/javasebusiness/downloads/java-archive-downloads-javase5-419410.html#jdk-1.5.0_22-oth-JPR
Extract the downloaded archive (chmod +x the bin and run), then copy the files to /usr/lib/jvm/java5
Rename the jdk1.5.0_022 or anything to jdk1.5.0 to make it simple.
Fix attributes:
sudo chmod a+x /usr/bin/java
sudo chmod a+x /usr/bin/javac
sudo chmod a+x /usr/bin/javaws
sudo chown -R root:root /usr/lib/jvm/java5/jdk1.5.0
Then run:
sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/java5/jdk1.5.0/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/java5/jdk1.5.0/bin/javac" 1
Now chose the jdk 5 as default
sudo update-alternatives --config java
And selecting the appropriate option.
Check that it worked
java -version
You should see something like this:
java version "1.5.0_22" Java(TM) 2 Runtime Environment, Standard
Edition (build 1.5.0_22-b03) Java HotSpot(TM) 64-Bit Server VM (build
1.5.0_22-b03, mixed mode)
Now you can run the setup.jar file in the extracted directory (istemp...)
sudo java -jar setup.jar
I recommend that you chose a contemporary java by running
sudo update-alternatives --config java
again.
When running the installer.sh, use the command line option "-is:javahome [path to your java jre folder]".
For instance, I installed below a java 8 jre on an old matlab compiler 2007b as follow:
sudo /opt/installer.sh -console -is:javahome /usr/lib/jvm/java-8-openjdk-amd64/jre/
I had same problem. The problem is you are installing 64-bit matlab on 32-bit ubuntu. use 32-bit matlab and install in ubuntu 32-bit. use 64-bit matlab and install in ubuntu 64-bit. Please like the answer if it was helpful.
I have to start by saying that I have just switched to Ubuntu from Windows and I am new to Linux in general. Coming from Windows, I really am not familiar with how exactly the permissions work, the Linux file system, where I am able to create folders that I can use without the sudo command etc.
I use eclipse on a daily basis for android development and other simple java swing projects. I was able to download and extract the latest available version of eclipse (kepler) to this path: /opt/eclipse. Inside this directory is the eclipse executable and other eclipse related files.
I also installed the JDK and verified with the java -version command. It says:
java version "1.7.0_25"
Java(TM) SE Runtime Environment (build 1.7.0_25-b15)
Java HotSpot(TM) 64-Bit Server VM (build 23.25-b01, mixed mode)
I am running on a 64 bit CPU architecture so both programs are the 64 bit version.
Now, my problem is that if I open eclipse from the Unity dash or from the file explorer, it give me this error:
However if I run sudo eclipse in the terminal, everything runs just fine as long as I do it as the super user. I have a hunch that the JDK is installed in a folder that is restricted to normal users and only works if I run the sudo command but this is just a hunch. As I said, I am new to Linux and I am not really sure what I am doing wrong here, I am learning as I go. I need a good explanation as to how to make it start from the Unity dock without the sudo command. Thanks in advance!
You'll want to use the chmod command from the terminal to change the permissions on the Java folder. See this link for more information:
http://www.linux.org/threads/file-permissions-chmod.4094/
Well after running the which java cmd, I noticed that the path to the JDK from the eclipse.ini file was not pointing to the correct location. I fixed the path and now it works. I don't know how the sudo cmd overrides the eclipse.ini path to JDK but well, it works