You're right that Java's Hashmap only ever resizes upwards - the most common use case. However, if there's a need to remove that memory after clearing() then th

You're right that Java's Hashmap only ever resizes upwards - the most common use case. However, if there's a need to remove that memory after clearing() then the typical use case is to do something that allows the GC to sort it. E.g., var map = new HashMap<Bla, Bla>(); // Many things added to map // Many but not all things removed from map // to shrink it to size of remaining items map = new HashMap<>(map); Yeah, it's not nice, but the people who wrote the JDK are far smarter than me, so I figure they optimised for the 99% use-case, not the 1%.