Eclipse API: How to get IFile from an IProject using only the file name?

As stated in the title, I do not have the package names or information. I have a handle to the IProject and a String representing the name of the IFile.

The IFile is a .java class file, and the IProject is a Java project. Ideally, I would like to do this without assuming they are Java files/projects - but the assumption is okay for my purposes. Any suggestions?

If you want to get the file from IProject recursively, you can use IProject#members.

Example)

public IFile findFileRecursively(IContainer container, String name) throws CoreException {
    for (IResource r : container.members()) {
        if (r instanceof IContainer) {
            IFile file = findFileRecursively((IContainer) r, name);
            if(file != null) {
                return file;
            }
        } else if (r instanceof IFile && r.getName().equals(name)) {
            return (IFile) r;
        }
    }

    return null;
}

You can call the method as follows.

IFile file = findFileRecursively(project, "Foo.java");

If you want to find the file not recursively, you can use IProject#findMembers(String).