How does a private final HashSet Work?

Question

So from my understanding of final you can't change the value of variable after. In the case of a private final foo HashSet<>() = new HashSet<>() I can use foo as a HashSet and edit the values in it but I can't reassign foo right?

Answer 1

final will prevent you to assign any new value to the variable, but it won't make your object immutable.

In your example,

private final foo HashSet<String>() = new HashSet<>();
foo.put("bar");              // is correct
foo = new HashSet<>();       // will fail at compilation