I understand that ikvm uses openJDK but i will like to substitute openJDK with a JVM version of my own. Want to check is it possible and if so, how can i go about doing so?
Related
Heading says it all:
Java version information, tested on opensuse:
java version "10.0.1" 2018-04-17
Java(TM) SE Runtime Environment 18.3 (build 10.0.1+10)
Java HotSpot(TM) 64-Bit Server VM 18.3 (build 10.0.1+10, mixed mode)
Stacktrace:
java.lang.UnsupportedOperationException: Retrieving groups by name is not supported on this platform.
at kotlin.internal.jdk8.JDK8PlatformImplementations.getMatchResultNamedGroup(JDK8PlatformImplementations.kt:28)
at kotlin.text.MatcherMatchResult$groups$1.get(Regex.kt:260)
at kotlin.text.jdk8.RegexExtensionsJDK8Kt.get(RegexExtensions.kt:33)
Question: Will this be fixed?
I am pretty sure that I can get the first regex, but that might not be possible in many other cases.
Thanks for your help (sorry for formatting, posting from mobile website)
According to the issue KT-20865, this problem is fixed in Kotlin 1.3.20
It is reproduced in Android (Java 8). Use
REGULAR_EXPRESSION.toRegex().find(sample)?.groupValues?.getOrNull(1)
instead, where needed groups start from 1 (see also https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/-match-result/group-values.html).
I read a few posts about JVM at Stack Overflow and would like to download a binary copy of the Hotspot JVM, yet I am not able to find it on http://www.java.net.
Beside that, what is the difference between Hotspot JVM and JVMs found at Oracle
Is Oracle JVM good for a production website?
Overview:
This SO question may clear up your questions regarding "What is JVM, Hotspot and OpenJDK".
Basically:
JVM means Java Virtual Machine. The JVM is the underlying runtime that executes java bytecode. There are multiple different implementations out there, all implementing the Java Virtual Machine Specification
HotSpot is the most used implementation of the JVM concept. It is used in both, Oracle JDK and OpenJDK. Oracle's JDK can be downloaded on oracle's website, currently http://www.oracle.com/technetwork/java/javase/downloads/index.html. This is "the typical JVM you will find on a normal user's windows machine".
OpenJDK is the open source project maintaining and impelmenting the HotSpot JVM, but also many other projects beside the JVM such as Graal or VisualVM. On Ubuntu for example you can install this OpenJDK (current version 8) by running sudo apt-get install openjdk8.
Conclusion:
While this explaination is not really perfect, it may be good enough to understand that there is no big difference between Oracle JDK and OpenJDK. If you are interested in a little more info on this, have a look at the SO question Differences between Oracle JDK and Open JDK
JDK / JVM sourcecode:
If you are interested in the source code, OpenJDK is the way to go. Here you can find the current OpenJDK 8 (which includes the HotSpot JVM). Its source code can be found here. It also states how to download the source code:
The jdk8u-dev forest for ongoing development can be cloned using this command: hg clone http://hg.openjdk.java.net/jdk8u/jdk8u-dev;cd jdk8u-dev;sh get_source.sh .
The corresponding master forest jdk8u can be cloned using this command: hg clone http://hg.openjdk.java.net/jdk8u/jdk8u;cd jdk8u;sh get_source.sh .
In addition, the source code for the last release, 8u66, is available by cloning the 8u master forest : http://hg.openjdk.java.net/jdk8u/jdk8u and using the 'jdk8u66-b17' mercurial tag.
OpenJDK currently does not have support for a JRE on MIPS processors (there's a port in progress, but who knows how long that will take).
I'm trying to understand how the JRE works, and what is standing in the way of using OpenJDK on our embedded system running Linux on a MIPS processor. If I have a custom JVM that is capable of running on MIPS designed to work with OpenJDK (in this case, I'm referring to JamVM 2.0), is there anything else preventing the JRE from running on the MIPS board? Are any other parts of the JRE platform-dependent?
My understanding is that the JRE is (mostly) composed of two units: the virtual machine, which abstracts the hardware and which is platform-dependent, and the collection of Java libraries which run on the virtual machine and which are not platform-dependent.
To be clear, my questions is: aside from the JVM, is any part of the Java Runtime Environment platform-dependent?
"aside from the JVM, is any part of the Java Runtime Environment platform-dependent?"
That depends on where you place the boundary where the VM ends and the JRE begins. I would consider memory management and code execution as 'the VM', everything more specific part of the JRE.
Thats means every binding to the operating system, be it I/O, Graphics etc. is part of the JRE. Thus the JRE has many platform dependent parts; you usually just don't notice them because your code uses their abstractions (e.g. File, Socket, Window).
So when you say "a port to MIPS" it doesn't mean anything without specifying an OS (ok, your link says Linux); a VM ported to a processor architecture by itself does not make a working java environment. It also requires a port of the native parts of the JRE that allow the java program to actually communicate with things outside the VM; thats where the OS platform comes in.
Since Linux is already supported for x64, the MIPS port should be able to reuse most of the JRE to platform bindings from that.
I have WebSphere 7 Aplication Server. There is Java VM 1.6 installed. Linux.
Java version "1.6.0"
Java(TM) SE Runtime Environment (build pxa6460sr10fp1-20120321_01(SR10 FP1))
IBM J9 VM (build 2.4, JRE 1.6.0 IBM J9 2.4 Linux amd64-64 jvmxa6460sr10fp1-20120202_101568 (JIT enabled, AOT enabled)
J9VM - 20120202_101568
JIT - r9_20111107_21307ifx1
GC - 20120202_AA)
JCL - 20120320_01
I try to use jProfiler, using trial lisence. But don't want to change something on the server this time.
So I download jprofiler for linux to my server.
Then I run bin/jpenable and it says that:
No unprofiled JVM found
Now I don't know what to do, googling doesn't give any useful result. Can You tell me in what way I must search a problem? May be incorrect path or something else. I hope You'll understand my english (it is not so good).
Have a look at this help pdf, in specifically check out Attach to local JVM session.
Also, have a look at this answer and this question.
hope it will help..
I understand that the Oracle Java SE contains closed source extensions and tools that are not part of the OpenJDK however is the Oracle Java SE JVM identical to the OpenJDK JVM or does Oracle make changes to the OpenJDK JVM before releasing it as a Java SE JVM?
Update 1:
I found some info from the JDK7 updates projects: http://openjdk.java.net/projects/jdk7u/qanda.html
Will the 7 Update Project receive security fixes from Oracle?
Yes.
As with OpenJDK 6, security fixes are first kept confidential and applied to a private forest before being pushed to the public forest as part of the general synchronized publication of the fix to effected JDK release trains. In addition, they will not go through the public code review and putback approval process, and their corresponding issues in the Project's issue tracker will not be publicly visible.
OpenJDK is the reference implementation of Java as of version 7.
OpenJDK 7 is the starting point for the version that Oracle distributes as Oracle JDK. Other vendors (e.g. RedHat for IcedTea) may also use OpenJDK as their starting point.
In terms of the differences between OpenJDK and a vendor VM, there may be patches which a vendor wants to apply but which the overall OpenJDK community has not accepted into mainline.
Vendor VMs must, of course, be able to prove that they are in conformance with the TCK if they want to use the Java trademarks to describe their product.
Oracle JDK is also not open-source. This is possible because of Java's dual licensing arrangements, and the fact that Oracle own Java overall.
Do you have more specific questions - as posed, your question is a bit vague. What specific aspects are you interested in?