Extension incorrectly runs cached `.class` file from another class of same name with no `package`

Bug report

Suppose there is a file structure:

folder1/
    Main.java
folder2/
    Main.java

// folder1/Main.java
public class Main {
    public static void main(String[] args) {
        System.out.println("Main 1");
    }
}

// folder2/Main.java
public class Main {
    public static void main(String[] args) {
        System.out.println("Main 2");
    }
}

No package statements; the projects are not connected at all.

When folder1/Main.java is run first, it gives the correct output Main 1.
But if folder2/Main.java is then run, it gives the wrong output of Main 1 instead of Main 2; the first built file is run instead.
folder1/Main.java 'shadows' folder2/Main.java, since the class name is the same and there are no package statements.
Another file structure that causes this is ./Main.java, ./folder/Main.java

This bug is inconvenient when multiple different, unrelated Java projects are in the same workspace.

Reproduce the issue by running folder1/Main.java and then folder2/Main.java, including the ./Main.java and ./folder/Main.java layout. Trace how the extension selects cached compiled classes; done means each unrelated Main.java runs its own output, including after the other file has already been run.