Set Interface

A Set is a collection that cannot contain duplicate elements.

HashSet

• Backed by a HashMap.
• No guarantee of order.
• Allows null values.
• Fastest set.

import java.util.HashSet;

HashSet<String> cars = new HashSet<String>();
cars.add("Volvo");
cars.add("Volvo"); // Will be ignored
System.out.println(cars); // [Volvo]

LinkedHashSet

• Preserves insertion order.
• Slightly slower than HashSet.

TreeSet

• Stores elements in sorted ascending order.
• Slower (log n time cost).

Interactive Code

Try to add duplicates!

Quiz

Next Steps

We have Lists and Sets. But how do we store Key-Value pairs? Maps.