So basically, at school our machines have an older version of the Java JDK installed, and I want to work on a netbeans project on home. I have it set up through the github and wanted to know if switching between JDK versions will mess up my project at all, if the older version will allow me to even open the newer version. And, if I can't, was curious on how to open a project in an older version of the JDK.
Thanks!
You just simply need to not use language features introduced after the version your school uses. Netbeans will give you hints if you attempt to use something when the version doesn't support it however (e.g. Diamond operators in 6, or using Lambdas when not using Java 8). So overall I would say you shouldn't be running into any issues, you can even make netbeans recognize the sources as an older version of Java by right clicking your project, and going to:
Properties > Sources > Source/Binary > 1.6 (Or whatever version you need)
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I want to install Java on a few different servers for running a third party service on tomcat.
I am not a Java developer and I got a bit confused when I began searching for the installer.
I checked the different Java versions and their long term support dates.
It seems that Java 11 JDK is - LTS so i decided to use it.
But when I was trying to find a runtime version (JRE?) since this is the version I am supposed to install on the server(?) I only found Java JRE 8.X.X, and this got me confused.
There is no higher major version of the JRE?
How does it work if you use the JDK 11 or even 14-15 as a developer and then use Java 8 JRE on your deployed servers?
Maybe the JDK holds inside of it the Java 8 JRE version?
Or do you actually need to install the JDK version on the servers instead?
The JRE is a subset of JDK. It contains everything needet to run Java applications but no support for development. So, if you need a JRE, a JDK is also good, although it conatins much stuff that you will not need.
Normally, for executing a Java application, you need a JRE with the same version or higher than the JDK used for development. But the developer can advise the compiler to generate code for a lower version. If he does so, he cannot use the features of the higher versions. For example the compiler of JDK 1.8 can produce code for JRE 1.6. You should consult the manual, to see which old versions are supported by the compiler of a specific version.
After some research,
It seems there is no separate JRE section anymore.
Also JDK 11 for production is not free and I guess this is an ongoing trend for the near future.
On a side note there is the open JDK 11 version but it does warn you about outdated security updates.
So basically in my case sticking to updated Java JRE 8 version is good enough for the near future.
I am using JDK8 on my normal desktop and I have a separate linux box that I am trying to run the Java program on.
The problem I'm running into is that the linux box is running jdk7, so the computer has JRE7 basically that it is running off of. My question is, is it possible to create a jar file in JDK8 that will be compatible with java 7?
I'm using IntelliJ to compile. I tried to compile in 1.7, but it gave an error when I did end up trying to do it. I compile it here:
In 1.8 it works fine to compile, but when I try to compile in 1.7 it doesn't work.
I know the short answer is to update the linux to JRE 8. But I am curious, is there a way to make it backwards compatible? Or is the other answer to simply install JDK7 on the desktop in order for it to run on the linux box using JRE7?
Java programs built with JDK 8 will only run on machines running JRE 8 (or higher).
I found this when trying to compile classes on my local Linux machine (using JDK 8) and deploying to a remote server running JRE 7. The classes just wouldn't work (like you're finding).
If you want to use JRE 8 on linux, I recommend using the oracle-java8-installer package from webupd8team. Installation instructions found here (assuming Debian based distro).
If you want to compile to JDK 7, it's not good enough to only have JDK 8 installed and pick to compile 1.7. You need JDK 7 installed to and restage your project to use JDK 7.
The thing you have to remember is that the difference between JRE/JDK versions is not just the extra features developers can use (e.g Lambda functions) but it's also that the JRE itself is improved (efficiency, garbage collection, etc.).
As a extreme example: If you wrote code that only used JDK 1 features but compiled it using JDK 8, it wouldn't run on a machine running JRE 1 because the Java classes had been compiled with JRE 8 in mind.
Do note though, that if you're Java Code uses only features from JDK 7 or 6 etc., you might think it good practice to compile using the minimum JDK required to allow for compatibility with more machines. Well...you'd have that compatibility but at a cost of using inefficient, out of date, possibly vulnerable compiled classes (At little extreme, but you get my point).
Are you using any new Java 8 features? Because if you are, this means you cannot build the project against the JRE7.
If you are not using any Java 8 features, you can build to Java 7 most easily by downloading the JDK7 and switching the project to use that instead of the JDK8.
You should also set project language level to 1.7 (and module language level(s) as well, if they're different). It's done in Project Structure settings dialog. After that the project should compile.
Note that you shouldn't use any of the APIs that appeared in 1.8, but such usages will most likely be highlighted in the editor.
This may seem a daft question so I will be as brief as possible.
Where I work, we deal with lots of Java apps that are compiled on old versions of Java, in fact we recently upgraded one of them to Java 1.6
We've been given new laptops recently with no admin rights and Java 7 installed by default.
I am presently unable to get hold of and install a copy of JDK 1.5 (which I need)
In Eclipse, if I set my JDK Compliance level to 1.5 but the Installed JRE is 1.7
Which of these 2 statements is true... ?
1. I am building my code at Java 1.5 ?
2. I am building my code at Java 7 ?
I've seen and spoken to various people on this subject and I am still non-the-wiser.
It means the byte code that is generated from your source code will be compliant to the 1.5 JRE.
The syntax highlighter will not allow you to do things that were new to 1.6, 1.7 such as switching on strings.
Developing with a JDK higher than the target platform is in principle possible, using the "compliance settings" and/or target version switches with javac.
Its however not practically feasible for doing real development, as nothing will prevent/warn you from using the API's present in your installed JDK but not in the target platform.
If, for example you develop for java 1.4 using an installed 1.5, while the compiler will not let you use autoboxing (which was introduced in 1.5), but it will happily let you use (for example) Integer.valueOf(int). Which is not present in 1.4.
May be its a newbie question...
I want to use latest eclipse available. It requires Java 8. However, our company uses java 6 for all projects.
So:
Should I download eclipse that is compatible with Java 6 only ?
or I can configure Java 6 for all the projects regardless what eclipse uses?
Would there be any issues, if its possible to use two versions (one for eclipse and another one for project)?
I know its a newbie questions. But the search did not yield a proper response.
no, you can use the latest Java for Eclipse. The JDK used for project can be configured per project or per workspace. You can install as much JDKs as you desire. i.e. You can start Eclipse using a 32Bit JDK while using a 64Bit JDK for Java EE-Servers or Projects, it has basically nothing to do with the JRE used for Eclipse. You just need to set it up.
I have developed a Java Application in Eclipse using JDK 1.7.0, the application runs and everything works as expected.
Now I would like to send the application to a colleague of mine who is using a different version of the JDK. He is using 1.6.x.
I am not interested in him opening up the application and debugging through it in Eclipse. I would only like him to run it. If I make a runnable .jar of the application and send that to him, would it work even though he has a different JDK installed on his machine?
Thank You.
You need to compile it using JDK 1.6 (or lower). Provided your code doesn't use features from Java 7, you won't have to change anything in your sources
It would work if your colleague had a newer JRE than the JDK you used to compile it. All versions of JRE are backwards-compatible with all class files built with previous versions, but the opposite can clearly not work because new versions introduce new features. Your colleague will get an UnsupportedClassVersionError.
However, it is easy to set up in Eclipse the target class version for your project: go to Project Properties, Java Compiler, and under JDK Compliance choose the version 1.6.
Needless to say, this will fail if your source code uses any features or library calls which the version 6 does not support.