bash : java : command not found (Fedora) - java

On Fedora I installed (or at least tried to install) JDK-18. I rebooted my laptop and wanted to check if it succeeded. I used java --version, but it said bash : java : command not found.

Well all that I will write is subjective. It all depends upon how did you install java in Fedora. If you downloaded the jdk distribution and unzipped it to some folder. Then in your .bashrc, you need to provide the path where the binaries are available
export PATH=$PATH:/path/to/java/installation/folder/bin
You can also look at sdkman
https://sdkman.io/
This is a nice tool to manage your JDK(s) regardless of Linux distribution you are using. (disclaimer: I have no affiliation with sdkman - i find this tool very helpful)

Related

macOS - How to install Java 17

Could someone please let me know the steps to install Java on a Mac.
I did brew install java
I get this
Warning: openjdk 17.0.1 is already installed and up-to-date.
To reinstall 17.0.1, run:
brew reinstall openjdk
If I do java -version, I get this.
openjdk version "13.0.8" 2021-07-20
If I have navigate to /Library/Java, I have 2 empty directories.
Where is java 17 installed??
In 2023, even if you can use just brew..
brew install openjdk#17
Java will be installed here:
/usr/local/opt/openjdk#17/bin/java
For the system Java wrappers to find this JDK, symlink it with:
sudo ln -sfn /usr/local/opt/openjdk/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk.jdk
...give a try to sdkman, it's far better than brew
curl -s "https://get.sdkman.io" | bash
then open a new shell and try list to see what you could install ;-)
sdk list java
At time of writing you could use:
sdk install java 17.0.4.1-tem
Java will be installed here:
/Users/freedev/.sdkman/candidates/java/17.0.4.1-tem
Java doesn't mind if you install multiple versions. This is often required; java is not backwards compatible (it tries to change little, but e.g. the java8 to java9 transition broke a ton of stuff, much of it needless and much of it not reasonably expectable or fixable by libraries and apps, so a bunch of java apps and libraries only run on java8 - just an example).
So, yes, you have installed JDK17. Also, yes, if you just run java without specifying which one you want, you so happen to get java13 here.
To see all installed javas, you can run:
/usr/libexec/java_home -V
to 'override', you can use something like (depends on which shell you're using on your mac):
export JAVA_HOME=`/usr/libexec/java_home -v 17`
(the backticks mean: Run this then take the output of it and treat that as the 'value' of the expression. here, assign it to the JAVA_HOME env var. -v 17 requests a path to java 17. The -V option lists all and is meant for your eyeballs, not for scripts. The -v option is mostly for scripting, and that's how we're using it here).
JAVA_HOME decides which java is used by some things, but the java you get when you just type java is /usr/bin/java, and that executable is actually just a wrapper that picks a java to run from amongst all installed versions. It uses JAVA_HOME to decide which java to actually run. There are wrappers for all the common commands (javac, too). You can always run e.g. which javac to see what that actually runs; you probably see /usr/bin/javac. Everything in /usr/bin is one of these wrapper thingies that looks at JAVA_HOME and then runs the binary it finds there.
To specify version 17
brew install openjdk#17
Later I add create a link:
sudo ln -sfn /usr/local/opt/openjdk#17/libexec/openjdk.jdk \
/Library/Java/JavaVirtualMachines/openjdk-17.jdk
And use jenv to control which java version to use
To used the version installed by homebrew rather than the one installed by the OS you can get detailed information from homebrew by typing
brew info java
Currently it states
For the system Java wrappers to find this JDK, symlink it with
sudo ln -sfn /opt/homebrew/opt/openjdk/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk.jdk
openjdk is keg-only, which means it was not symlinked into /opt/homebrew,
because macOS provides similar software and installing this software in
parallel can cause all kinds of trouble.
If you need to have openjdk first in your PATH, run:
echo 'export PATH="/opt/homebrew/opt/openjdk/bin:$PATH"' >> ~/.zshrc
For compilers to find openjdk you may need to set:
export CPPFLAGS="-I/opt/homebrew/opt/openjdk/include"
For Homebrew, the package that installs the new AdoptOpenJDK is named as temurin. So you need to use below command:
brew install --cask temurin17
If you get any error like temurin cask not available then update brew using below commands:
brew update
brew tap homebrew/cask-versions
To switch quickly between different versions of java add the entries in bashrc as per your jdk versions like:
alias j8="export JAVA_HOME=`/usr/libexec/java_home -v 1.8`; java -version"
alias j17="export JAVA_HOME=`/usr/libexec/java_home -v 17`; java -version"
Steps to install
You asked:
let me know the steps to install Java on a Mac.
Download an installer free-of-cost from vendors such as Adoptium, Azul Systems, Bellsoft, Amazon, Oracle, Microsoft, SAP, and others.
Run installer app.
Quit the installer app when done.
Verify installation by typing on a command-line in Terminal.app:java --version
Delete installer app that you downloaded.
Configure your IDE to use that new Java implementation you installed.
Java location
You asked:
Where is java 17 installed??
/Library/Java/JavaVirtualMachines/
In the Finder, choose Go > Go to Folder, and paste /Library/Java/JavaVirtualMachines/.
Note that this is not the Library folder within your home folder. We are not referring to /Users/your_user_name/Library/…. We are referring to the root Library folder that applies across all the user accounts on this Mac.
You said:
I did brew install java
No need for the Homebrew package manager. If you already enjoy using the brew tool, proceed. But if new to Homebrew, skip it if your only goal is to install Java. Just use an installer for Java as you would for many Mac apps.
JavaFX
You added a tag for javafx.
Be aware that for JavaFX, you have two options:
Include the necessary OpenJFX libraries within your development project and within your final app, or …
Use a JDK that includes the JavaFX/OpenJFX libraries.
At least two vendors provide JDK installers that include the JavaFX/OpenJFX libraries:
Azul Systems (ZuluFX)
Bellsoft (LibericaFX)
This answer is specifically if you use Intellij on a Mac
Within IntelliJ, you can use the IDE to add new JDKs of selected versions from common vendors. Instructions for this are here:
Setup the project JDK
When setting up the JDK, you can either:
Select a pre-existing JDK which has been registered with the IDE OR
Use the Add JDK option to add a new JDK which you previously downloaded and installed using the method outlined in Basil's answer OR
Use the Download JDK option to choose a vendor and version of the JDK that the IDE will automatically download, install and make available for selection.
The JDKs installed by Idea will be located in the same location as outlined in Basil's answer for a manual install /Library/Java/JavaVirtualMachines/.
One common issue is that the version of the JDK registered for the project differs from the default version used in the terminal. This can sometimes mean that the app works when run in Idea, then fails when run in the terminal (or, at least that it is executed against a version of the JDK you didn't expect).
To select the version of the JDK to run in the terminal, configure the Java home setting as outlined in rzwitserloot's answer.
export JAVA_HOME=`/usr/libexec/java_home -v 17`
Also, some tools such as the openjfx maven plugin will not use the java version selected in Idea when executing a call to a JDK tool like jlink, but will instead have their own mechanism for finding a JDK to use (e.g. look at JAVA_HOME or use the Maven toolchains plugin). So it is always good to check the JAVA_HOME variable and ensure that it is set to a reasonable value, both for terminal execution and for effective use of Java development tools that may rely on it.
I think that answers here are not fully out of topic, but from my point of view, my case is exactly the same as that of the author. I had already installed java 8, 11, and 13. All of them resides at:
/Library/Java/JavaVirtualMachines/
Nevertheless when I tried to find the path of JDK 17 it resides:
/usr/local/Cellar/openjdk
I use Mac OS Big Sur and the JDK was installed with homebrew
Brew now supports searching old formulae and allowing you to install a specific version. I'm using Homebrew 3.5.2-117-gb941470
Create a local tap: brew tap-new --no-git local/openjdk
Ask Brew to find the formulae of the version you want: brew extract --version 17.0.2 openjdk local/openjdk
Install Java 17 using your new local tap: brew install openjdk#17.0.2
Link the JDK into the MacOS JVM Dir: sudo ln -sfn /usr/local/opt/openjdk#17.0.2/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk17.0.2.jdk
Check Java 17 is available: /usr/libexec/java_home -V
Set Java Home: export JAVA_HOME=$(/usr/libexec/java_home -v17)
Check current version of Java is correct...
$ java --version
openjdk 17.0.2 2022-01-18
The following method installs Java without the need for any additional tools or package managers.
Go to https://jdk.java.net/17/ and download the latest macOS archive.
Download the latest Adoptium release for the Java 17 branch by going to https://adoptium.net/temurin/releases/ and be sure to select the tar.gz version.
The archive is either for x64 (Intel CPU) or for AArch64 (Apple Silicon / M1 CPU).
Then, open a Terminal, and extract the downloaded archive to the system path for Java virtual machines:
cd Downloads
tar xzf OpenJDK17U-jdk_aarch64_mac_hotspot_17.0.5_8.tar.gz -C /Library/Java/JavaVirtualMachines

get java installation path using shell script in rhel

I have to automate a process in which i need to install java on RHEL 7, using rpm package and then update the security jars later on the installed location. Once i execute the java rpm, how would i get the correct installed path? when i execute which java it says /bin/java. However, i need the installation location using shell script.
Here, the actual installation happened at /usr/java/jdk1.7.0_55/jre. I want to get this location. Can some one suggest me how to retrieve this?
The readlink program (part of coreutils, and available on any RHEL version) can resolve symbolic links:
foo=$(readlink -f $(which java))
echo $foo
(You may also have realpath, but perhaps not).
Java RPM packages from Oracle support the 'alternatives' system, which provides the detail you are seeking. For example, after installing a recent JRE, 'alternatives' reports like so:
[user#host ~]$ alternatives --display java
java - status is auto.
link currently points to /usr/java/jre1.8.0_60/bin/java
etc...
The output is relatively friendly for scripting.

pyCharm debugging: JRE without jstack?

I need to debug pyCharm community version on Windows 7 and try to follow what their manual says:
JStack
This command line utility is provided with the JDK installation and
can be found in JAVA_HOME\bin directory. Make sure to use the same or
close JDK version to the one the IDE runs under (see Help | About). It
will not work if IDE runs under 32-bit JDK and you run jstack from the
64-bit JDK distribution and vice versa.
To use jstack you need the IDE process identifier (PID). PID can be
obtained using jps utility that is located in the same directory as
jstack.
jps -mv
My pyCharm: help/about reads: JRE 1.7.0_40 b43 x86
How ever, in C:\Program Files (x86)\Java\jre7\bin there is no jps and no jstack. I'm not used to the command line in Windows - perhaps I'm doing something wrong here? Am I supposed to look in a different directory? I could not find any system wide environmental variable JAVA_HOME what could give any clues here.
Well, you need a Java Development Kit (JDK) instead of a Java Runtime Environment (JRE).
It is a bit larger but has many other dev tools (like jstack, jps, jvisualvm, etc., even the source code of Java). Download and install one to see the differences.

Installing JDK from self extracting bin on Cygwin

I want to install the JDK in cygwin on my windows machine. I am downloading the linux version of JDK from oracle site using wget command. Here is the list of commands I am running to install JDK:
wget http://download.oracle.com/otn-pub/java/jdk/6u31-b04/jdk-6u31-linux-x64.rpm.bin
chmod a+x jdk-6u31-linux-x64.rpm.bin
./jdk-6u31-linux-x64.rpm.bin
All these instructions are same as suggested by Oracle for installing JDK over here but I am getting the following errors:
Firstly, those messages indicate that what you are trying to execute is an HTML document! In other words, the download has failed and given you an error page rather than an installer.
However, assuming that you succeed in downloading the (Linux) installer, it is unlikely that it will install properly, and there is about ZERO chance that the installed tools will run. Applications that have been compiled for Linux don't run on Cygwin.
What you need to do is to download and install the JDK for Windows, and then tweak your cygwin profile a bit. This page explains: http://horstmann.com/articles/cygwin-tips.html.
(If you Google for "java cygwin" there are various other tips for making Java work from Cygwin. However, in my experience there are a few rough edges ... due to the fact that the Windows Java utilities expect to have been called with windows-style arguments, pathnames, classpaths, etcetera.)

How to update JAVA SDK using command prompt

I have JAVA SDK 1.7.0.170 installed on my windows 7, I need to upgrade to 1.7.0.250. Is there a command line option?
Any equivalent of PIP for python updates?
Not really. But what you can do is to install Java on one computer and then ZIP the folder where the files were installed. To install on all the other computers, just unzip the archive, set JAVA_HOME and change the PATH variable.
If that's too much work to do manually, you can try to create a custom installer.
Note that this might violate the EULA; if you do this for a company, have legal check this.
You can't do this from the command line for Oracle's JDK as you must accept their license agreement on their web site before you can download.
You could download and install the latest OpenJDK using wget and run the installer. (two commands) You would need to change your environment settings which might be possible using a command line regedit, but I always use the windows configuration for this.

Categories