Why hashmap is faster than hashset

HashSet is backed by HashMap internally, so the only difference is the auto-boxing of your dummy 0. Could you separate io and tokenizing from map inserting, just to be sure you're not focusing on the wrong thing?

Add a comment. Active Oldest Votes. You could use a more memory-efficient Collections library. You can get an empty instance of this by doing: ObjectDoubleMaps. Boschi Boschi 2 2 silver badges 10 10 bronze badges. Sign up or log in Sign up using Google. Sign up using Facebook.

Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta. Now live: A fully responsive profile.

Visit chat. Linked Related HashMap holds the data as key-value pairs where as HashSet holds the data as only objects. There are also some similarities exist between them. In this post, we discuss some of the differences and similarities between HashMap Vs HashSet in java. HashSet implements the Set interface which in turn extends the Collection interface, the top level interface in the Java Collection Framework.

HashSet stores the data as objects where as HashMap stores the data as key-value pairs. HashSet is sometimes considered as a wrapper around the HashMap. If you try to insert duplicate element, HashSet will be unchanged. If you look at the source code of HashSet at least JDK 6, 7 and 8 , it uses HashMap internally, so it basically does exactly what you are doing with sample code.

If the only thing you need your collection for is to check if an element is present in there - use Set. Your code will be cleaner and more understandable to others. None of these answers really explain why HashMap is faster than HashSet. They both have to calculate the hashcode, but think about the nature of the key of a HashMap - it is typically a simple String or even a number.

Calculating the hashcode of that is much faster than the default hashcode calculation of an entire object. If the key of the HashMap was the same object as that stored in a HashSet, there would be no real difference in performance.

The difference comes in the what sort of object is the HashMap's key.