Comparing Java HashSet, TreeSet, and LinkedHashSet performance.

test.java

import java.util.*;

public class test{
	// Conclusion
	// use HashSet...
	// ...unless you have few accesses and mostly only build them, in which case LinkedHashSet is faster
	// ...and only use TreeSet when you need the order
	
	final static int size = 500;
	final static int accesses = 10;
	final static int repeats = 1000;

	public static void doLoop(Set<Integer> testSet) {
		for (int i = 0; i < size; i++) {
			testSet.add(i);
		}
		for (int i = 0; i < accesses; i++) {
			testSet.contains(i%size);
		}
		for (int i = 0; i < size; i++) {
			testSet.remove(i);
		}
	}
	public static void main(String[] args) {

		Set<Integer> testSet;
	 
		long startTime = System.nanoTime();

		for (int j = 0; j < repeats; j++) {
			doLoop(new HashSet<Integer>());
		}

		long endTime = System.nanoTime();
		long duration = endTime - startTime;
		System.out.println("      HashSet: " + duration/repeats);
	 
		startTime = System.nanoTime();

		for (int j = 0; j < repeats; j++) {
			doLoop(new TreeSet<Integer>());
		}

		endTime = System.nanoTime();
		duration = endTime - startTime;
		System.out.println("      TreeSet: " + duration/repeats);
	 
		startTime = System.nanoTime();

		for (int j = 0; j < repeats; j++) {
			doLoop(new LinkedHashSet<Integer>());
		}

		endTime = System.nanoTime();
		duration = endTime - startTime;
		System.out.println("LinkedHashSet: " + duration/repeats);
	 
	}
}