I want to run a jdk1.4 compiled jar on jdk1.6.
Will there be anything wrong about it.
JVM is forward compatible, so I think there will be no problem.
Is it true.
As of the Java byte code, the compiled code should be backward compatible with increasing JRE versions. This means that in general, a v6 JVM should be able to run code that is compiled with a v4 JDK. (While the JRE is backward compatible, the Java compiler is forward compatible, i.e. v4 source code is supposed to be compilable by a v6 compiler.)
However, you can run into problems with the libraries that the v4 code is compiled against when the code is run on a v6 JRE. You can find an overview of API changes from v4 to v6 on this webpage.
Related
I downloaded and installed JDK8u33 for ARM on my beaglebone black, and according to this documentation (http://docs.oracle.com/javase/8/embedded/jdk-arm-8u6/index.html) javafx is included and supported.
However, I can not find jfxrt.jar anywhere in the JRE or JDK, and using javac on a simple javafx program yields "javafx.application" is not a package.
What gives?
As #eckig says, since the 8u33 for ARM version, Oracle has removed JavaFX from the ARM distribution.
To run any JavaFX application you can downgrade your version to the last JDK8u6 that supported JavaFX, or you can provide a valid jfxrt.jar.
And you can do it following this tutorial, cross building OpenJFX for ARM, or just using some already built distribution like this one hosted on the JavaFXPorts project.
Once you have downloaded armv6hf-sdk.zip, unzip it and you need to add this command line option to attach this external source to the classpath, with the extension mechanism:
-Djava.ext.dirs=<path to armv6hf-sdk>/rt/lib/ext
For instance, you need this to run one of the JavaFX old samples from its actual path:
sudo /opt/jdk1.8.0_33/bin/java -Djava.ext.dirs=<path to armv6hf-sdk>/rt/lib/ext -jar BrickBreaker.jar
The latest version of the Java Development Kit for ARM processors (JDK 8u33 for ARM) no longer supports JavaFX Embedded, it has been all of the tech news, for example here: http://jaxenter.com/jdk-arm-without-javafx-end-javafx-embedded-114212.html
This should be easy, but I can't figure out how.
Is there any way to find out which JavaFX version is installed. And I DON'T mean programmatically via System.getProperty("javafx.runtime.version") , which returns an empty string on my computer, although JavaFX is installed.
I would rather like to have something like java -version on console, but in order to get the JavaFX version.
Alternatively it would be sufficient to know if JavaFX is installed at all. I just have some customers who can't run my swing/javaFX app and would like to tell them to check whether JavaFX is installed.
You can't really do this the same way you do with the Java runtime. The difference is that java is a machine executable that launches the JVM. JavaFX is just a set of library classes; it's not really an executable in the same sense.
It looks like the System property that you can read at runtime is kept in jre/lib/javafx.properties, so you can do something like
cat $JAVA_HOME/jre/lib/javafx.properties
or whatever the Windows equivalent is, if you're running on Windows. However, if the System property you get at runtime is blank, then I suspect this file doesn't exist. As dfeuer commented, it would help to know your JRE version.
Update:
The relationship between JDK/JRE version and JavaFX version is as follows.
Beginning with JRE 1.7.0 update 6, JavaFX was included with the JRE, but was not on the classpath. So for JRE 1.7.0, update 6 and later, the jfxrt.jar file is included in JAVA_HOME/jre/lib. The javafx.properties file which contains the JavaFX version information is in the same directory, though in theory at least the JRE version will determine the JavaFX version (since they were shipped together).
Just inspecting the JDK 1.7.0 versions I have installed on my machine, the mapping from JDK version to JavaFX version is:
/Library/Java/JavaVirtualMachines/jdk1.7.0_06.jdk javafx.runtime.version=2.2.0
/Library/Java/JavaVirtualMachines/jdk1.7.0_10.jdk javafx.runtime.version=2.2.4
/Library/Java/JavaVirtualMachines/jdk1.7.0_11.jdk javafx.runtime.version=2.2.4
/Library/Java/JavaVirtualMachines/jdk1.7.0_13.jdk javafx.runtime.version=2.2.5
/Library/Java/JavaVirtualMachines/jdk1.7.0_17.jdk javafx.runtime.version=2.2.7
/Library/Java/JavaVirtualMachines/jdk1.7.0_21.jdk javafx.runtime.version=2.2.21
/Library/Java/JavaVirtualMachines/jdk1.7.0_25.jdk javafx.runtime.version=2.2.25
/Library/Java/JavaVirtualMachines/jdk1.7.0_40.jdk javafx.runtime.version=2.2.40
/Library/Java/JavaVirtualMachines/jdk1.7.0_45.jdk javafx.runtime.version=2.2.45
Beginning with JRE 1.8.0, JavaFX was included with the JRE and was placed on the classpath; so it's effectively a full part of the core libraries. In version 1.8.0, the jfxrt.jar file is in JAVA_HOME/jre/lib/ext (which automatically makes it part of the classpath). The javafx.properties file which contains the JavaFX version information is still in JAVA_HOME/jre/lib. The version numbering for JavaFX in version 1.8.0 (appears to) simply mimic the JRE version:
/Library/Java/JavaVirtualMachines/jdk1.8.0.jdk javafx.runtime.version=8.0.0
/Library/Java/JavaVirtualMachines/jdk1.8.0_05.jdk javafx.runtime.version=8.0.5
/Library/Java/JavaVirtualMachines/jdk1.8.0_20.jdk javafx.runtime.version=8.0.20
So with your customers, you can simply ask them to do java -version and for the most part, you'll be able to deduce the JavaFX version. On some rare occasions you may need to dig a little deeper.
A sort-of-related note: if you are shipping an application to customers and you need to determine a specific version, consider using a self contained application, in which you include a JRE (and JavaFX runtime) with the application.
For Ubuntu 18.04 the JavaFX version can be found in /usr/share/openjfx/lib/javafx.properties. A simple command should show you the version you have.
$ cat /usr/share/openjfx/lib/javafx.properties
javafx.version=11.0.2-internal
javafx.runtime.version=11.0.2-internal+0-2019-02-19-093139
javafx.runtime.build=0
Perhaps your installation has something similar?
If you are using Netbeans 15 on Windows 10, look in the file:
C:\Program Files\NetBeans-15\netbeans\javafx\VERSION.txt
On my machine, it contains 11
A straightforward issue for java new comer:
IMO, Java should keep backward compatible, so a jar built with JDK5 should work on JRE6 or high environment, but the converse case should fail.
However from the netty page,
https://github.com/netty/netty/tree/netty-4.0.17.Final,
I found the following:
You require the following to build Netty:
Latest stable Oracle JDK 7
Latest stable Apache Maven
Note that this is build-time requirement. JDK 5 (for 3.x) or 6 (for 4.0+) is enough to run your Netty-based application.
This really confuses me, could anyone can help explain this?
Yes, if you specified proper -source and -target option to the javac. Netty's pom.xml specifies -source 1.5 and -target 1.5 to ensure that.
My development team recently was forced over to a remote development environment where we do not have full access to the servers. Before the change over we had a JAR that was running fine on Java 1.7 x64 along with JRE 7. When we moved over to the new server our JAR was running alright, but then one of the server admins "updated" our Java to an older version and uninstalled the one we were using. Don't ask me why, I don't know. I re-installed Java 1.7 and uninstalled 1.6 along with the JREs.
The following problem occurs at runtime, there are no build errors:
Registry key 'Software\JavaSoft\Java Runtime Environment\CurrentVersion'
has value '1.7', but '1.6' is required.
Error: could not find java.dll
Error: could not find Java SE Runtime Environment.
I've run the same JAR on my laptop with no issues. Both the server and my laptop have JDK 1.7 and JRE 7 in the respective %HOME% variables and system PATH. I've even reinstalled JRE 6 and placed it later in the system environment PATH variables with the same result.
I have also changed the registry back to look at 1.6 and it results in the following, which I looked up and it appears to be from having multiple Javas installed (leading back to my original problem):
Exception in thread "main" java.lang.UnsupportedClassVersionError: ... :
Unsupported major.minor version 51.0
I would appreciate any insight you all have as I have been looking over various forums but nothing seems to have exactly my problem. Also, this has happen on another server we are using as well. Thanks!
Update: No luck with recompiling the JAR to either 1.6 or 1.7 and matching the JDK. Also, why in the world would a newer version of Java break an older compiled version?
This happens when you somehow confused java itself. You are trying to run a java 6 VM where it found a JRE 7. It might show this problem even if you type in the command line just java or java -version in a misconfigured environment. The JAR is not the problem, except in the very unlikely case where the code in JAR is looking in the Windows Registry for that (which probably is not your case).
In my case, I had the java.exe, javaw.exe and javaws.exe from Java 6 in the Windows/System32 folder (don't know how it got to be there). The rest of the JDK and JRE where found in the PATH inside C:\Java\jdk_1.7.0\bin. Oops!
Just had the similar error when installing java 8 (jdk & jre) on a system already running Java 7.
Error: Registry key 'Software\JavaSoft\Java Runtime
Environment'\CurrentVersion' has value '1.8', but '1.7' is required.
Error: could not find java.dll Error: Could not find Java SE Runtime Environment.
My environment was set up correctly (Path & java_home correctly defined), but the problem arises from the way pre-8 Java installers worked, which is that they used to copy the three executables (java.exe, javaw.exe & javaws.exe) to the Windows system directory. These remain unless overwritten by a new pre-8 installation.
However the Java 8 installer instead creates symbolic links in a new directory, C:\ProgramData\Oracle\Java\javapath, pointing to the actual JRE 8 location.
This means that you'll actually run the old 7 exes but use the new 8 DLLs.
So, the solution is simply to delete the 3 Java exes, as above, from the windows system directory.
If you are running 32-bit Java on a 64-bit Windows, the exes would be in Windows\SysWOW64, otherwise in Windows\System32.
I've deleted java files at windows/system32 and I also have removed c:\ProgramData\Oracle\Java\javapath from the PATH variable, because there was 3 symlinks to java 1.8 files.
I had JDK 1.7 in the %JAVA_HOME% variable and java1.7/bin in the PATH.
PS1: My problem was between Java 1.7 and Java 1.8.
PS2: I can't add this as a comment to Victor's answer because I haven't enough points.
In the START menu type "regedit" to open the Registry editor
Go to "HKEY_LOCAL_MACHINE" on the left-hand side registry explorer/tree menu
Click "SOFTWARE" within the "HKEY_LOCAL_MACHINE" registries
Click "JavaSoft" within the "SOFTWARE" registries
Click "Java Runtime Environment" within the "JavaSoft" list of registries here you can see different versions of installed java
Click "Java Runtime Environment"- On right hand side you will get 4-5 rows . Please select "CurrentVersion" and right Click( select modify option) Change version to "1.7"
Now the magic has been completed
I don't know if anyone is still following this thread, but I recently had this issue when I tried to launch ActiveMQ 5.10 as a Windows service.
I didn't have a JAVA_HOME path set.
I had Java 6 and Java 7 installed, but the default version was v7. (ie if I opened a command window and types "java -version").
This is where the clue was - "java -version" returned "Java HotSpot(TM) 64-Bit Server VM (build 23.1-b03, mixed mode)" but I was had installed the Win32 service...
It turns out that if you use the Win32 wrapper on a 64-bit machine it somehow decides to use a different version of Java...
So my fix was to uninstall the 32-bit version of the wrapper and install the 64-bit version.
aversion on my machine; just habit I guess... But luckily I resolved the issue eventually...
For my Win7
Paradox was in being java.exe and javaw.exe in System32 folder.
Opening that folder I couldn't see them but using search in Start menu I get links to those files, removed them. Next searsh gave me links to files from JAVA_HOME
magic )
Change to directory with correct java.exe i.e. go to the required JDK version java.exe
cd C:/Program Files/Java/jdk1.7.0_25/bin
Run the java.exe from this directory, it has precedence over registry and $PATH settings.
java -jar C:/installed/selenium-server-standalone-2.53.0.jar
I solved this problem by uninstalling Java 1.8
The jar was compiled to be 1.6 compliant. That is why you get this error. Two resolutions:
1) Use Java 1.6
OR
2) Recompile the jar to be compliant for your environment 1.7
Using regedit, remove the entries corresponding to java 7. It will work.
So I know you can use ant and mvn to test the project, but I was wondering if there was a way to deploy the project directly as a executable jar or otherwise compile it into a format that can be directly ran? Thanks!
if you are serious about making a launchable desktop program (and especially if its going to be a game), you should use launch4j to make an exe file that launches the jar. It isn't hard to use, and it makes the program much more end user friendly
If your project was generated from the 1.7.2 PlayN archetype or newer, that functionality is already built in. Simply invoke:
mvn package
and a dependencies-included jar file will be generated in:
yourgame/java/target/yourgame-java-1.0-SNAPSHOT-jar-with-dependencies.jar
you can test it by running it standalone like so:
java -jar yourgame/java/target/yourgame-java-1.0-SNAPSHOT-jar-with-dependencies.jar
If your game was generated via an older PlayN archetype, the you can add the necessary bits to your java/pom.xml file by pasting in this in (merging with any existing <build> <plugins> blob):
maven-assembly-plugin
2.4
jar-with-dependencies
${mainClass}
make-assembly
package
single
Then just run mvn package as above to generate the file. Note that you will need to be building against PlayN 1.7.2 or newer as that version is the first one that supported automatic unpacking of the LWJGL native libraries needed to run on the desktop.