Running multiple times a simple snippet could lead to a memory leak.

DataFrame df = DataFrame
        .foldByColumn("1", "2")
        .ofStream(IntStream.range(0, Integer.MAX_VALUE / 8));

JShell defines local variable df multiple times and could generate several synthetic classes that will hold the data of that variable, while there's no class unloading right now implemented.

Workaround for this is just restart kernel in the Jupyter.