Both java 8 and java 11 are installed on a server, default settings (JAVA_HOME) show java 11.
Is it possible to run the code with java 8 without creating the jar file or by selecting java 8 while running the jar file?
I'm not sure what your use case is; why you think you need to specify a version. However:
Your choice of "java version" is usually determined by which "java" you choose to run.
If you're using an IDE, you can select one or the other JVM.
If you're running from a shell script or a .bat file, you can specify a different path, e.g. C:\Program Files\java\jdk-11.0.1\bin or C:\Program Files\java\jre1.8.0_121\bin.
If you're on Linux, you can use update-alternatives to specify a different "default" Java version.
You can also specify -version:release on your Java command line.
Q: Does that answer your question?
I made a Runnable Jar that will run as service in windows, but the final pc that will execute him, has 3 versions of java installed, 1.3, 1.6 and 1.7, and my jar needs to be executed with 1.7, because him uses classes that are present only in 1.7+ version, o don't know how are configured the environiment variables, my question is:
Is possible to force my code to run in java 1.7?
You can also do this without persistently resetting your path environments. Just use the absolute path to your jre/jdk instead of typing "java": e.g.: "C:\Program Files\Java\jre7\bin"\java -jar foo.jar, same goes for MacOS and Linux.
Set your JAVA_HOME and PATH environment variable to point to the Java 7 directory.
See https://superuser.com/questions/284342/what-are-path-and-other-environment-variables-and-how-can-i-set-or-use-them to know how to do it.
Rather than setting path/classpath at top level, you should create a
batch file and set path/classpath there.
Then command to run your jar.
I am shipping a executable jar file to customer, Customer has installed JRE 5, JRE 6 and JRE 7 on the box. My Jar required JRE 7 to run.
Without changing the system PATH (Environment var) how can I specify the JRE 7 to use?
You can specify full path to that JRE that you need, for example:
/path/to/jre/bin/java.exe -jar executable.jar
or
/path/to/jre/bin/javaw.exe -jar executable.jar
If you run this from a shell (script) then it is good practice to first set the JAVA_HOME environment variable to the right location before (/path/to/jre) before running the executable. You could first set/export JAVA_HOME and then extend it to the location of the Java executable (e.g. %JAVA_HOME%\bin\java.exe on Windows). More information here.
I'm not sure there's a cross-platform way to achieve this.
On Windows you can use a tool such as launch4j to wrap up the jar as a .exe that can select an appropriate JRE.
On Mac OS X you can have several different JDKs installed in parallel but only one public JRE (which will be at least the latest version out of the installed JDKs, and may be newer if it's been auto updated). It's the public JRE that is used for app bundles and when double clicking a JAR in finder.
The simplest way to do this, is to use Java WebStart to launch your program and then specify you need a suitably new version of Java. The launcher will then locate a suitable distribution on your system to use.
Using javaws also allows you to easily distribute new updates to your users.
Caveat: Caching has notoriously been a problem over the years. Ensure that when a jar changes content, its URL changes too.
I'm trying to learn java, and since I'm using 'javac' and 'java' all day, I'm using vim as my editor of choice. But I'm having a problem getting this system to work: I can't even get a minimal "Hello World" program to run! Within vim, I can use :!javac % to compile the current file just fine. However, with a file Test.java, any attempt to call :!java Test yields an UnsupportedClasVersionError, even though the same command works fine outside of vim. I'm completely stumped.
I'm using java7 on windows 7 (64bit) with cmd.exe as my shell.
The Java you invoke is an older version than the Javac you invoke.
You most likely have a Java 6 JRE installed (for browser plugins etc) at system level and a Java 7 JDK installed which you've added at the end of your path.
Either tell Javac to produce Java 6 compatible class files (with -target) or put the JDK in the front of your path.
We have a couple of applications running on Java 5 and would like now to bring in an application based on Java 6. Can both java versions live together under Windows?
Is there any control panel to set the appropriate Java version for different applications, or any other way to set up, what version of Java will be used to run that particular application?
Of course you can use multiple versions of Java under Windows. And different applications can use different Java versions. How is your application started? Usually you will have a batch file where there is something like
java ...
This will search the Java executable using the PATH variable. So if Java 5 is first on the PATH, you will have problems running a Java 6 application. You should then modify the batch file to use a certain Java version e.g. by defining a environment variable JAVA6HOME with the value C:\java\java6 (if Java 6 is installed in this directory) and change the batch file calling
%JAVA6HOME%\bin\java ...
I was appalled at the clumsiness of the CLASSPATH, JAVA_HOME, and PATH ideas, in Windows, to keep track of Java files. I got here, because of multiple JREs, and how to content with it. Without regurgitating information, from a guy much more clever than me, I would rather point to to his article on this issue, which for me, resolves it perfectly.
Article by: Ted Neward: Multiple Java Homes: Giving Java Apps Their Own JRE
With the exponential growth of Java as a server-side development language has come an equivablent
exponential growth in Java development tools, environments, frameworks, and extensions.
Unfortunately, not all of these tools play nicely together under the same Java VM installation. Some
require a Servlet 2.1-compliant environment, some require 2.2. Some only run under JDK 1.2 or above,
some under JDK 1.1 (and no higher). Some require the "com.sun.swing" packages from pre-Swing 1.0
days, others require the "javax.swing" package names.
Worse yet, this problem can be found even within the corporate enterprise, as systems developed using
Java from just six months ago may suddenly "not work" due to the installation of some Java Extension
required by a new (seemingly unrelated) application release. This can complicate deployment of Java
applications across the corporation, and lead customers to wonder precisely why, five years after the
start of the infamous "Installing-this-app-breaks-my-system" woes began with Microsoft's DLL schemes,
we still haven't progressed much beyond that. (In fact, the new .NET initiative actually seeks to solve the
infamous "DLL-Hell" problem just described.)
This paper describes how to configure a Java installation such that a given application receives its own,
private, JRE, allowing multiple Java environments to coexist without driving customers (or system
administrators) insane...
It is absolutely possible to install side-by-side several JRE/JDK versions. Moreover, you don't have to do anything special for that to happen, as Sun is creating a different folder for each (under Program Files).
There is no control panel to check which JRE works for each application. Basically, the JRE that will work would be the first in your PATH environment variable. You can change that, or the JAVA_HOME variable, or create specific cmd/bat files to launch the applications you desire, each with a different JRE in path.
We can install multiple versions of Java Development kits on the same machine using SDKMan.
Some points about SDKMan are as following:
SDKMan is free to use and it is developed by the open source community.
SDKMan is written in bash and it only requires curl and zip/unzip programs to be present on your system.
SDKMan can install around 29 Software Development Kits for the JVM such as Java, Groovy, Scala, Kotlin and Ceylon. Ant, Gradle, Grails, Maven, SBT, Spark, Spring Boot, Vert.x.
We do not need to worry about setting the _HOME and PATH environment variables because SDKMan handles it automatically.
SDKMan can run on any UNIX based platforms such as Mac OSX, Linux, Cygwin, Solaris and FreeBSD and we can install it using following commands:
$ curl -s "https://get.sdkman.io" | bash
$ source "$HOME/.sdkman/bin/sdkman-init.sh"
Because SDKMan is written in bash and only requires curl and zip/unzip to be present on your system. You can install SDKMan on windows as well either by first installing Cygwin or Git Bash for Windows environment and then running above commands.
Command sdk list java will give us a list of java versions which we can install using SDKMan.
Installing Java 8
$ sdk install java 8.0.201-oracle
Installing Java 9
$ sdk install java 9.0.4-open
Installing Java 11
$ sdk install java 11.0.2-open
Uninstalling a Java version
In case you want to uninstall any JDK version e.g., 11.0.2-open you can do that as follows:
$ sdk uninstall java 11.0.2-open
Switching current Java version
If you want to activate one version of JDK for all terminals and applications, you can use the command
sdk default java <your-java_version>
Above commands will also update the PATH and JAVA_HOME variables automatically. You can read more on my article How to Install Multiple Versions of Java on the Same Machine.
It should be possible changing setting the JAVA_HOME environment variable differently for specific applications.
When starting from the command line or from a batch script you can use set JAVA_HOME=C:\...\j2dskXXX to change the JAVA_HOME environment.
It is possible that you also need to change the PATH environment variable to use the correct java binary. To do this you can use set PATH=%JAVA_HOME%\bin;%PATH%.
I use a simple script when starting JMeter with my own java version
setlocal
set JAVA_HOME="c:\java8"
set PATH=%JAVA_HOME%\bin;%PATH%;
java -version
To have a java "portable"
you can use this method here:
https://www.whitebyte.info/programming/java/how-to-install-a-portable-jdk-in-windows-without-admin-rights
Or use links. While it is rather unpleasant to update the PATH in a running environment, it's easy to recreate a link to a new version of JRE/JDK. So:
install different versions of JDK you want to use
create a link to that folder either by junction or by built-in mklink command
set the PATH to the link
If other version of java is to be used, delete the link, create a new one, PATH/JAVA_HOME/hardcoded scripts remain untouched
Invoking Java with "java -version:1.5", etc. should run with the correct version of Java. (Obviously replace 1.5 with the version you want.)
If Java is properly installed on Windows there are paths to the vm for each version stored in the registry which it uses so you don't need to mess about with environment versions on Windows.
If you use Java Web Start (you can start applications from any URL, even the local file system) it will take care of finding the right version for your application.
Using Java Web Start, you can install multiple JRE, then call what you need.
On win, you can make a .bat file:
1- online version:
<your_JRE_version\bin\javaws.exe> -localfile -J-Djnlp.application.href=<the url of .jnlp file.jnlp> -localfile -J "<path_temp_jnlp_file_.jnlp>"
2- launch from cache:
<your_JRE_version\bin\javaws.exe> -localfile -J "<path_of_your_local_jnlp_file.jnlp>"