HashTableHashMapTimer.java

package assign09;

import java.util.HashMap;
import java.util.Random;

/**
 * This class tests the performance of remove and containsKey
 * for Java's HashMap and our HashTable classes.
 * 
 * @author Paul Nuffer and Nils Streedain
 *
 */
@SuppressWarnings("unused")
public class HashTableHashMapTimer {
	
	private static String allCharacters = "abcdefghijklmnopqrstuvwxyz";

	public static void main(String[] args) {
		Random rng = new Random();
		System.out.println("N\tnanoTime");
		
		int incr = 1000;
		for (int probSize = 1000; probSize <= 100000; probSize += incr) {

			int timesToLoop = 1000;
			
//			HashTable<String, Integer> hashTable = new HashTable<>();
			HashMap<String, Integer> hashMap = new HashMap<>();

			for (int j = 0; j < probSize; j++) {
				StringBuilder stringBuilder = new StringBuilder();

				for (int k = 0; k < rng.nextInt(20); k++)
					stringBuilder.append(allCharacters.charAt(rng.nextInt(26)));
				
				String string = stringBuilder.toString();
				
//				hashTable.put(string, 0);
				hashMap.put(string, 0);
			}

			// First, spin computing stuff until one second has gone by.
			// This allows this thread to stabilize.
			long stopTime, midpointTime, startTime = System.nanoTime();
			while (System.nanoTime() - startTime < 1000000000) {}

			startTime = System.nanoTime();
			for (int i = 0; i < timesToLoop; i++) {
				StringBuilder stringBuilder = new StringBuilder();

				for (int k = 0; k < rng.nextInt(20); k++)
					stringBuilder.append(allCharacters.charAt(rng.nextInt(26)));
				
				String string = stringBuilder.toString();
				
//				hashTable.remove(string);
//				hashMap.remove(string);

//				hashTable.containsKey(string);
				hashMap.containsKey(string);
			}

			midpointTime = System.nanoTime();

			// Capture the cost of running the loop and any other operations done
			// above that are not the essential method call being timed.
			for (int i = 0; i < timesToLoop; i++) {
				StringBuilder stringBuilder = new StringBuilder();

				for (int k = 0; k < rng.nextInt(20); k++)
					stringBuilder.append(allCharacters.charAt(rng.nextInt(26)));
				
				String string = stringBuilder.toString();
			}

			stopTime = System.nanoTime();

			// Compute the time, subtract the cost of running the loop
			// from the cost of running the loop and searching.
			// Average it over the number of runs.
			double averageTime = ((midpointTime - startTime) - (stopTime - midpointTime)) / (double) timesToLoop;

			System.out.println(probSize + "\t" + String.format("%.5f", averageTime));
		}
	}
}