Problem when using PSI to parse Java

I'm trying to use the PSI tree structure for parse Java files and manipulate them for security purposes, following the documentation that i found here https://plugins.jetbrains.com/docs/intellij/psi.html

The problem is most of the suggested methods to retrieve Psi from Files seems not working for me, only two with unwanted result:

1

 // Recognize correctly the type but with no children
 var localDef = PsiManager.getInstance(project).findViewProvider(LightVirtualFile(fileName, file.readText(Charset.defaultCharset())))
 var local = PsiJavaFileImpl(localDef)
 return local

2

    // Recognize wrongly the type as ANY with no children
    var localDef2 = CoreLocalFileSystem().findFileByIoFile(file)!!
    val local2 = PsiManager.getInstance(project).findFile(localDef2)!!
    return local2

Any idea / suggestion about?

P.S. Thanks to everyone who will try to reply, even with this small part of code, unfortunately i can't share more