Empirical Comparison between manually versus default Binary Search Algorithm

BinarySearchComparison.java

package examples.algorithms;

import java.util.Arrays;
import java.util.stream.IntStream;

import com.google.common.base.Stopwatch;

/**
 * Binary Search comparison against Java's default Binary Search algorithm.
 * Manually is better in this case!
 *
 * @author Andre Luis de Oliveira Dias (https://about.me/andreluisdias)
 * @since 30 de set de 2017
 */
public class BinarySearchComparison { // JAVA 8
	
	public static void main(String[] args) {

		BinarySearchComparison main = new BinarySearchComparison();
		
		// Define data
		final int[] data = main.getData();
		final int elementToSearch = 10000000;

		// Arrays.binarySearch
		Stopwatch w1 = Stopwatch.createStarted();
		int idx = Arrays.binarySearch(data, elementToSearch);
		if (idx < 0) idx = -1;
		w1.stop();
		main.printResult(idx, w1, "default");
		
		Stopwatch w2 = Stopwatch.createStarted();
		int idxManually = main.binarySearch(data, elementToSearch);
		w2.stop();
		main.printResult(idxManually, w2, "manually");
		
		assert (idx == idxManually); // use JVM hint -ea to turn this on
	}
	
	private int[] getData() {
		return IntStream.range(1, 10000).toArray();  // [1,30]
	}
	
	private int binarySearch(final int[] data, final int key) {
		
		int lo = 0, hi = data.length -1;
		
		while (lo <= hi) {
			int mid = lo + (hi - lo) / 2;
			if  (key < data[mid]) hi = mid -1;
			else if (key > data[mid]) lo = mid + 1;
			else return mid;
		}
		
		return -1;
	}
	
	private void printResult(final int idx, final Stopwatch sw, final String prefix) {
		System.out.println(String.format("(%s) Found idx %s within %s", prefix, idx, sw.toString()));		
	}
}

Try it by yourself

Added line below to do the final assertion...

if (idx < 0) idx = -1;