Benchmark for StackOverflow

StringsContainingCharacters.java

package stackoverflow;

import java.util.HashSet;
import java.util.Random;
import java.util.Set;

public class StringsContainingCharacters {

	public static void main(String[] args) {
		
		Strategy straight = new StraightStrategy();
		Strategy trie = new TrieStrategy();
		
		String[] sources = generateSources(100 * 1000, 14);
		String input = randomString(4);
		
		Benchmark benchmark = new Benchmark(sources, input);
		
		System.out.println("Straight took " + benchmark.exec(straight, 10) + "ms on average");
		System.out.println("Trie took " + benchmark.exec(trie, 10) + "ms on average");
	}

	static class StraightStrategy implements Strategy {
		
		@Override
		public void test(String[] source, String input) {
			
			Set<Character> needle = removeDuplicates(input);
			
			for (String src: source) {
				if (contains(src, needle)) {
					System.out.println(src);
				}
			}
		}
		
		private boolean contains(String haystack, Set<Character> chars) {
			for (char c: chars) {
				if (haystack.indexOf(c) < 0)
					return false;
			}
			return true;
		}
		
		private Set<Character> removeDuplicates (String input) {
			Set<Character> chars = new HashSet<Character>();
			
			for (int i = 0; i < input.length(); i++)
				chars.add(input.charAt(i));
			
			return chars;
		}
		
	}
	
	static class TrieStrategy implements Strategy {

		@Override
		public void test(String[] source, String input) {
			// TODO
		}
		
	}
	
	interface Strategy {
		void test(String[] source, String input);
	}

	static class Benchmark {
		
		String[] sources;
		String input;

		Benchmark(String[] sources, String input) {
			this.sources = sources;
			this.input = input;
		}
		
		// Returns the average execution time
		long exec(Strategy strategy, int times) {
			long start = System.currentTimeMillis();
			
			for (int i = 0; i < times; i++) {
				strategy.test(sources, input);
			}
			
			return (System.currentTimeMillis() - start) / times;
		}

	}

	static String[] generateSources(int howMany, int lineLength) {
		String[] src = new String[howMany];
		
		for (int i = 0; i < src.length; i++)
			src[i] = randomString(lineLength);

		return src;
	}

	static String randomString(int length) {
		char[] src = new char[length];
		Random generator = new Random();

		for (int i = 0; i < src.length; i++)
			src[i] = (char) generator.nextInt(128);

		return new String(src);
	}
}