My Java applet only supports 1.4 java run time(1). I am having one machine on which both Java 1.4 and 1.6 environment is installed. Is there some setting available by which I can make sure my applet will always use Java 1.4 run time when it runs?
We are using key event class private data array bData with the help of Java reflection. The data which is there in this array JDK 1.4 and 1.6 is different in both the version.
A Java application compiled with JDK 1.4 will run on JDK 1.6.
You can compile a Java application with JDK 1.6, but compatible with JDK 1.4 by configuring the 'source level'.
Although you can choose your default JDK to be safe, but it depends on your operating system. If you are on Linux, you can choose between available Java versions using pdate-alternatives --config java command (which will modify some symlinks in the hindsight).
On Windows 7:
Control Panel -> Programs -> Java
Select 'Java' tab, and View the Java Runtime Environment settings.
Ensure that your Java 1.4 entry is selected.
There's a way to force a specific installed version to run, but if one Java plugin replaces the other there might be an issue with this. See linked question for further details.
Force Internet Explorer to use a specific Java Runtime Environment install?
Are there any issues with running the 1.4 code on 1.6? If not, you should be fine. Just avoid using anything in the classpath that changed significantly between these versions. Otherwise, look [here][1]. The codebase download thing is interesting, since it lets you download a different classpath. So, regardless of the JRE version, you could force the download of a 1.4 JRE classpath, which should ensure full compatability.
Edit: found an updated guide to using previous classpaths with newer Java versions in applets, which actually seems to work:
http://download.oracle.com/javase/tutorial/deployment/applet/deployingApplet.html
Edit 2: I actually have it working, but it appears to need to download JRE 1.4 and install it, but then it will run the applet with it automatically. However, this might be suitable for your needs.
http://www.2shared.com/file/bl3Rua2e/applet.html -- extract the archive, and then run index.html inside this. All source code is included.
Related
I've been working with Java for a bit now and the JDK/JRE version has given me quite a bit of trouble lately. I am developing using the Intellij IDEA IDE and it of course uses the latest version of the JDK, 14. However when I attempt to execute software compiled with JDK 14 outside the IDE, I get an error that the JRE isn't new enough to run this software. So I updated Java on my computer and another machine and attempt to run again without any success. After some digging, I tweaked my machine to use the JRE included in the JDK 14 which is compatible.
However it is kind of odd that I had to do that, one would think that the latest version of java should of been enough to run applications made with the latest version of the JDK (14). Right now Java is version 8 build 251 and says there is no newer update available. If JDK 14 is out for a while now, why would they not update the version of Java they ship?
The problem is partially solved, as only the machine I am using for development is capable of executing the created applications. Other people I've sent them to have been unable to run them, despite having the latest version of java. Also it is a pain to get the latest JDK, especially when having limited experience on how to get rid of old versions, change path point to the latest version, get the right package (open/oracle JDK) and do that for windows and several distrubutions of linux. What is going on? Did I get Java from the wrong place and everyone else as well? Why are oracle doing this and why are there no java updates since clearly there exists a newer version?
Starting with Java-11, separate JRE does not exist anymore. In other words, if you are using Java-11 or above, you should care about JDK only.
You should uninstall JRE-8 from your machine and make sure your JDK-14 bin folder in the PATH variable. Some application even requires JAVA_HOME to work and therefore you should make sure that your system has an environment variable called JAVA_HOME and its value set to the root folder of JDK-14 (i.e. one level above your JDK bin).
Q: What should my clients do to run my application compiled on JDK-14?
Ans: Your clients must install JDK-14. Also, check this thread for some alternatives.
You're confusing how IntelliJ or JDK are used on the OS. IntelliJ, now, often comes with its JDK binaries (but even this can be configured, IntelliJ can be configured to use any JDK/JRE build you'll provide to it); however, if you run your Java application out of IntelliJ, most likely you're using Java installed locally on your OS, which might be referenced via your JAVA_HOME environment variable.
I'd suggest to:
Check java -version in your shell (and hence you'll see what JVM instance your OS spins up when you run a Java application);
Check where java (on Windows, or which - on Linux) in your shell, to see all the Java binaries available on your OS.
Try to uninstall Java SE Development Kit and Java JRE(if you have both in your machine) and reinstall both again, JDK and JRE both, I am sharing my google drive link where you can find the latest version of both JDK and JRE and when you are done installing, add there bin folder path in the Environment Variables of your machine.
I have one question in my mind and I should note that I know the differences between JDK and JRE. I am not a new programmer in Java.
What I would like to ask is in Eclipse I can specify the compilation environment (correct me if I a wrong) in window> Preferences but we can also change it for a specific project.
OK. I added jre and jdk folder in the options. I can use both.
But JRE has no javac (no java compiler) in it. So how it is possible that some projects requires that I need to change to jre1.7 to COMPILE?
I was getting some minor.major version error and setting JRE solved my problem?
How can this be possible?
In fact now I realized something.
Ok the question changes a little.
I saw that these are VM not compiler. I understood.
Does JDK have also JRE in it? so if I specify JDK1.8 I am setting jre1.8 as VM and if I specify JRE1.7 I am setting jre1.7 as VM?
Is it right?
It makes confusions. Why JDK has JRE in it?
JDK has whole JRE (regular Java VM) inside, in order to allow you to run what you will develop with it.
Theoretically someone could make some small-JDK with just tools and without JRE, but it would make a whole lot more confusion as to which tools version run with which JVM version (most JDK tools needs JVM to be run). Look at you, how many people have only this problem? So it is bundled together, tools and JRE as a whole named JDK, thanks to that you have some guarantee that those JRE and tools will work together.
JRE - Java Runtime Environment - allows you to run java programs
JDK - Java Development Kit - allows you to run and develop java programs
JDK = JRE + tools for developer
Also note, that You can choose for the java compilation process two things:
compatibility with source version - this is basically the syntax you are allowed to use.
compatibility with VM version - this is the minimum VM level on which you can run the compiled binaries.
example from your post: If you have compiled something as Java 8, you can't run it on Java 7, this is the minor/major version problem you have. But the opposite (to run something for Java 7 on Java 8) is valid.
in your example JDK8 and JRE7 both are just fully functional VM's, but JDK8 has additionally (in comparison to JRE) development tools inside it.
I'm trying to set the IntelliJ IDEA JDK to version 1.8 (because it's the latest). When I navigate to System/Library/Frameworks/JavaVM.framework IntelliJ IDEA shows 1.6. When I type java -version it shows 1.8. I found that command under "Finding default JDK on OSX" https://www.java.com/en/download/help/version_manual.xml
I'm confused what versions of the JDK I have... and where they are located. Appreciate any help.
Yes, you can. You have JDK 1.6 and 1.8 installed on your computer. According to the Jetbrains website, all their products require Apple JDK 1.6 to be installed in order to run on Mac.
To make IntelliJ IDEA use JDK 1.8, you will need to edit /Applications/<Product>.app/Contents/Info.plist file and change JVMVersion from 1.6* to 1.8* :
<key>JVMVersion</key>
<string>1.8*</string>
To start off java will usually uninstall any version of the JDK when you get an update. Secondly if you want to check to see what version you are running I would go into what ever you are using to program and see what version you are compiling under (For example netbeans or eclipse). If it says 1.8 that is what you are running and same for 1.6. If this is really becoming a super big problem all you have to is uninstall java then re install and it should fix it.
You can have many different versions of Java on your system. In general Java depends on environment variables and the PATH environment variable. Some programs and tools look for tool specific environment variables to allow you to use a specific version of Java for that particular tool.
In the case of IntellJ the link that Eddie B posted in his comment explains how IntellJ determines which "installation" of Java it should use.
I have a web Application and i need to upgrade java jre version from 6 to 7 .I am using Eclipse as IDE.I tried to update the Jre from eclipse .I have even updated the JAVA_HOME environment variable but i am getting following error
C:\Program Files\Java\jdk1.7.0_55\jre..\lib\tools.jar
Please ensure you are using JDK 1.4 or above and
not a JRE (the com.sun.tools.javac.Main class is required).
In most cases you can change the location of your Java
installation by setting the JAVA_HOME environment variable.
Thanks
Download java hereand install it as a common application.
Then in Eclipse use Window->Prefrences->Java->Installed JREs
#Roman Bondar I guesss OP wanted to know more than just the setting.
Basically, JREs are meant to be downwards compatible, so that you are able to execute java classes compiled with version 6 with a runtime from java 7.
But as always, there may be special cases when things have to be changed, e.g. container or libraries. I remember a case back when I migrated to java 6 that it required a special version of JBoss.
Check out this Oracle blog as a starting point.
is it true that the java -version command returns the java version for the java that I use to browse the web, but the java version that I use in netbeans / eclipse can be a totally different version?
In fact can the version of java i use in netbeans and eclipse be different?
Or is it that a system only has 1 version of java that works throughout all applications?
is it true that the java -version command returns the java version for the java that I use to browse the web,
No, it returns the version that's first in the system path. The browser may use a different version.
but the java version that I use in netbeans / eclipse can be a totally different version?
Yes
In fact can the version of java i use in netbeans and eclipse be different?
Yes
Or is it that a system only has 1 version of java that works throughout all applications?
No
The version of Java that is used in the browser is defined in the control panel. This defaults to the version that is returned by java -version. IE uses a JRE.
When NetBeans is installed, it asks which version of Java to use, so this is not necessarily the same as IE, alkthough it may default to the same version JDK.
NetBeans and Eclipse can be configured to use a different version of the JDK than the standard one, so you can't guarantee that IE and NetBeans/Eclipse use the same version of Java.
On Windows, you can have as many versions of Java on a machine as you want.
You van have several versions of java installed. In eclipse.ini you can specify what VM it will use.
No, It can have multiple. You can set the specific java version to be used for your application by setting classpath for your application.