Cannot Set Java Compiler Compliance Java 6 or 7 only Java 8 With JDK 6, 7 or 8

[jredfox]

Issue: Cannot Compile Project with java 6, 7 but ONLY java 8 while using JDK 6, JDK 7 or JDK 8 as the Alternate JRE.

ERROR: Compiling for Java version '1.6' is no longer supported. Minimal supported version is '1.8'

Versions:

• Eclipse Version 2025-09-R-win32-x86_64
• OS: Windows 11

Steps to reproduce:

• JDK-8 is the first in my path "C:\Program Files\Java\jdk-1.8\bin"
• Project --> Properties --> Java Build Path --> Alternate JRE --> Installed JRES --> JDK 6, JDK 7 or JDK 8
• Project --> Properties --> Java Compiler --> Notice No options to go below 1.8 compliance level even though JDK 8 suppose to support JDK 6 - 8 at the very least
• Project --> Clean
• Produces Error Compiling for Java version '1.6' is no longer supported. Minimal supported version is '1.8'

Also tried doing:

• Project --> Properties --> Java Compiler --> Installed JRE --> JDK 6, JDK 7 or JDK 8
• Project --> Properties --> Java Compiler --> Execution Environments --> JDK 6, JDK 7 or JDK 8

And if you try to run it you will get compilations for Java 8 only. Causing many errors like Unsupported major.minor version 52.0

[srikanth-sankaran]

This is not a bug but intended restriction.

[jredfox]

This is not a bug but intended restriction.

Intended restriction in what world? you can't compile 1.8(java 8) compliant jars on java 6 or java 7. perhaps you need to re-read what I had posted. If eclipse is suppose to not accept JDK 6 or JDK 7 then it would have restricted it from adding it to begin with. You realize alot of industrial companies are hard stuck on java 5 or java 6 still right?

JDK 8 has builtin support for compiler compliance levels from Java 3 - Java 8 which includes java 6 and java 8.

AGAIN how does one say it's working as intended when JDK 8 has compliance levels built into the compiler itself the work is done for you it's an argument added into the command line. Unless you also drop support for JDK 8 you have to support JDK 8 which JDK 8 has compliance levels for Java 3 - Java 8.

[jredfox]

Also it's not just me lots of people were complaining on stack overflow that they couldn't have java 6 or java 7 compliance levels with JDK 6, 7, or 8.

Examples of why it's needed:

• Your job uses java 6 and uses backend things that only work for java 6 or lower
• You use ASM library which only supports java 7 or lower and upgrading to a newer one breaks things
• You use a Reflection Library which doesn't fully work in java 8
• You want to debug an older program from java 6 without upgrading and re-writing it which doesn't involve you re-writing alot of code to simply figure out a bug which may not even be produced outside of java 6 aka invalid tests.
• You want to create a minecraft mod and Forge locks java to a certain version
• Eclipse is an IDE not a political landscape it shouldn't dictate nor care what major version of java you are using why you are using it or for who / how long you are using it. The limitions of the compliance level should be determined by the Alternate JDK not by eclipses "1.8" compliance enformecement which 1.8 JDK supports earlier versions baked in.
• etc....

[srikanth-sankaran]

Please see #2536

[srikanth-sankaran]

You realize alot of industrial companies are hard stuck on java 5 or java 6 still right?

You can use a version of Eclipse SDK prior to 4.33.

[jredfox]

Please see #2536

I already have stated it has to do with the alternative JDK you give eclipse not eclipse's default JDK that comes with eclipse. JDK 25 obviously isn't going to support compiling for java 5, 6 and 7 or maybe even 8. JDK 8 does support java 3 - 8. The argument in which you linked assumes you give eclipse JDK 17 or higher which isn't the case here you are giving eclipse the alternative JDK of JDK 8 or lower

There is 0 reason on why eclipse cannot support JDK 1 - 8 if it supports JDK 8. Java 8 is fully backwards compatible with java 1.1 and the bytecode remains basically the same. but your not even working with bytecode half the time are you your working on source files and using javac to compile them right? Everything in java 1 is inside of java 8. If you support 8 you can support java 3 -java 8 complier compliance levels

Yeah sure encourage people to use an eclipse whose dep links broke in 2015 rather then just fixing a simple bug. it is a bug as JDK 8 does indeed support compiling all the way through java 3 according to eclipse neon.

[trancexpress]

• Eclipse is an IDE not a political landscape it shouldn't dictate nor care what major version of java you are using why you are using it or for who / how long you are using it. The limitions of the compliance level should be determined by the Alternate JDK not by eclipses "1.8" compliance enformecement which 1.8 JDK supports earlier versions baked in.

Eclipse has its built-in Java compiler (ecj). Adding Java 1.6 on the classpath wont make Eclipse delegate to 1.6 javac. It will make ecj compile the code against Java 1.6 libraries.

So, similar to newer javac versions, ecj doesnt support some of the older source/target/release versions.

Eclipse does in fact care what major Java version you are using, since effort goes into supporting the respective language features. That effort becomes greater with the number of supported Java versions.

Similar to javac, you can use older Eclipse versions. Though note that at least on Linux it might not be trivial to set the right GTK+ environment up.

[jredfox]

versions

It worked last year and it doesn't work this year saying the removal is intentional doesn't make any sense. I tested eclipse 2024 on my macbook with JDK alternative JRE and was able to go to java 1.6 compliance without any issue.

Again I am talking about you give eclipse the alternative JRE / JDK of Java 8 or lower and then it use to allow you to go back to java 6, 7 or 8 without issues.

Also what exactly are you saying as to why you can't support Java 1 - 8 when java 8 was fully backwards compatible with java 1.1. If you guys supported java 8 there isn't alot of work to support past versions especially since you can just literally use the older compiler you wrote for those compliance levels.

[iloveeclipse]

Yeah sure encourage people to use an eclipse whose dep links broke in 2015 rather then just fixing a simple bug.

I assume you won't contrubute this simple fix?
With that, please try an older 4.32 Eclipse version from https://archive.eclipse.org/eclipse/downloads/ which still supports Java 6 compilation.

Note, I believe you misunderstand how Java support works in Eclipse. The compiler used in Eclipse is not taken from JDK, so using Java8 doesn't mean IDE would be able to compile for Java 6, because we don't use javac.

Beside this, I can fully understand your frustration but Eclipse (and JDT as part of it) is open source project and has limited resources. We decided, that with limited resources we have, the best way to move the project forward with supporting latest Java versions is to cut support for older Java versions. We can't have both simply because the code is extremely complex and implementing new features while keeping support for old ones requires lot of extra effort and resources we don't have.

Closing.

[jredfox]

closing this issue is why everyone moved from eclipse to jetbrains I will link them this issue and promote them thanks for ruining your own ides

[srikanth-sankaran]

If you use Eclipse 4.33 or later you cannot compile your project at source or compliance levels below 1.8.

Alternate JRE specification does not matter. As has been called out we don't use the compiler from the JRE/JDK. So what source compliance levels the alternate JRE levels support is immaterial.

[srikanth-sankaran]

Yeah sure encourage people to use an eclipse whose dep links broke in 2015 rather then just fixing a simple bug. it is a bug as JDK 8 does indeed support compiling all the way through java 3 according to eclipse neon.

Eclipse SDK 4.32 should compile your project at compliance levels 6 or 7 or 5.

If the links for that are broken please raise a defect.

Sarcasm is not a useful approach IMHO - thanks.

[jredfox]

This was the last eclipse that supports java 6 and java 7 if you give it JDK 6, 7 or 8. Notice it was released in 2024. It was claimed 2-3 years ago in issues that eclipse dropped java 6 and java 7 support and was intended and obviously java 6/7 didn't work then it got fixed. if this was true and it wasn't a bug then why in 2024-06-R does it still work? I think it's a bug or someone removed some code because it literally worked last year.
https://www.eclipse.org/downloads/packages/release/2024-06/r

I would report this to the actual eclipse bug reports but it seems to have gotten merged with github