Can I store 50 mb of string type key value pair data in Java Hash Map

Question

I want to store around 5 million unique strings in Java hash map. Key and value will be the same string. String maximum length will be 15 characters (ASCII).Later I want to lookup whether a particular string exists in the hash map.

Do i need to worry about the memory size issue for the above scenario. I am guessing like it wont need more than 75 mb to 150 mb memory.

Thanks in advance.

Answer 1

Key and value will be the same string.

Using a Map when its keys and values will be the same is redundant. You should use a Set instead, especially if you only plan to use contains .

Regarding your concern about space, let's assume that each String has a length of 15 characters.

Assuming you're using Java 9, Latin 1 characters only require a single byte , so 5 million unique String s will require at most 75_000_000 bytes or 75 MB .

Java 8 and below back their String s with char[] , so you'd essentially require twice as much memory in that case.