Help resolving Java Linkage Error

[thorn carbon]

Hello dear people,

I am currently doing university homework and am experiencing an error which I cannot seem to fix 😦.
This is the error message:

Exception in thread "main" java.lang.LinkageError: loader constraint violation: loader 'app' wants to load class Tree. A different class with the same name was previously loaded by com.sun.tools.javac.launcher.Main$MemoryClassLoader @6af93788. (Tree is in unnamed module of loader com.sun.tools.javac.launcher.Main$MemoryClassLoader @6af93788, parent loader 'app')
        at java.base/java.lang.ClassLoader.defineClass1(Native Method)
        at java.base/java.lang.ClassLoader.defineClass(ClassLoader.java:1013)
        at java.base/java.security.SecureClassLoader.defineClass(SecureClassLoader.java:150)
        at java.base/jdk.internal.loader.BuiltinClassLoader.defineClass(BuiltinClassLoader.java:862)
        at java.base/jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(BuiltinClassLoader.java:760)
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(BuiltinClassLoader.java:681)
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:639)
        at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
        at TreeListElement.toString(TreeListElement.java:34)
        at TreeList.toString(TreeList.java:20)
        at Tree.toString(Tree.java:32)
        at Tree.main(Tree.java:71)

[supple wraith]

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[thorn carbon]

If relevant, I can share the sourcefiles in question

As for my setup, I just have 3 files in a common folder and using java[c] directly

my files compile just fine, the error occurs once I try and run the main method in Tree.java

this is the folder structure for reference

just these files in the same folder

these are the sourcefiles

[boreal dawn]

so you are in the folder with the three source files and first run javac * and then java Tree and that produces the LinkageError ?

and there are no other files in that folder other than the mentioned source files ?

[thorn carbon]

yep

deleted the generated class files from previous compilatons just to be sure, still didnt work

[thorn carbon]

indeed that is what's happening

[boreal dawn]

what are the outputs of:
java --version
and
where java

[thorn carbon]

C:\Program Files\Java\jdk-19.0.1\bin\java.exe

[boreal dawn]

and you are running the compiled class files with java Tree not java Tree.java correct ?

[thorn carbon]

wait im actually not sure, let me try both

[boreal dawn]

the second one will produce the LinkageError

[thorn carbon]

oh wow, the first one works!!

thank you a lot mr fish sticks

[supple wraith]

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[thorn carbon]

but whats the semantic difference between those invocations

[boreal dawn]

In newer version of java. The java command can be used to run single file applications if the file in question is passed to the command with its extension java [filename].java. I assume that an internal javac classloader is completely separate from the "normal" classloader hierachy mening that when it tries to load the already compiled classes (that wouldn't be possible if the classes weren't compiled beforehand) it will throw that LinkageErrror. However, I can't give you a detailed explanation because I know too little about the inner workings of the java command.

[thorn carbon]

ah

thank you for everything!

[supple wraith]

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[thorn carbon]

.close