Added a Bloomfilter and fixed some bugs

src/zutil/test/BloomFilterTest.java

@@ -0,0 +1,64 @@
+package zutil.test;
+
+import java.text.DecimalFormat;
+import java.util.HashSet;
+import java.util.Random;
+
+import zutil.struct.BloomFilter;
+
+import junit.framework.TestCase;
+
+/**
+ * This code may be used, modified, and redistributed provided that the 
+ * author tag below remains intact.
+ * 
+ * @author Ian Clarke <ian@uprizer.com>
+ */
+
+public class BloomFilterTest extends TestCase {
+	public void testBloomFilter() {
+		DecimalFormat df = new DecimalFormat("0.00000");
+		Random r = new Random(124445l);
+		int bfSize = 400000;
+		System.out.println("Testing " + bfSize + " bit SimpleBloomFilter");
+		for (int i = 5; i < 10; i++) {
+			int addCount = 10000 * (i + 1);
+			BloomFilter<Integer> bf = new BloomFilter<Integer>(bfSize, addCount);
+			HashSet<Integer> added = new HashSet<Integer>();
+			for (int x = 0; x < addCount; x++) {
+				int num = r.nextInt();
+				added.add(num);
+			}
+			bf.addAll(added);
+			assertTrue("Assert that there are no false negatives", bf
+					.containsAll(added));
+
+			int falsePositives = 0;
+			for (int x = 0; x < addCount; x++) {
+				int num = r.nextInt();
+
+				// Ensure that this random number hasn't been added already
+				if (added.contains(num)) {
+					continue;
+				}
+				
+				// If necessary, record a false positive
+				if (bf.contains(num)) {
+					falsePositives++;
+				}
+			}
+			double expectedFP = bf.falsePosetiveProbability();
+			double actualFP = (double) falsePositives / (double) addCount;
+			System.out.println("Got " + falsePositives
+					+ " false positives out of " + addCount + " added items, rate = "
+					+ df.format(actualFP) + ", expected = "
+					+ df.format(expectedFP));
+			double ratio = expectedFP/actualFP;
+			assertTrue(
+					"Assert that the actual false positive rate doesn't deviate by more than 10% from what was predicted",
+					ratio > 0.9 && ratio < 1.1);
+		}
+	}
+
+
+}