Merge pull request #59 from satorg/geohash-with-bit-precision

add validation for negative numberOfBits in GeoHash.withBitPrecision

src/main/java/ch/hsr/geohash/GeoHash.java

@@ -61,6 +61,9 @@ public static GeoHash withCharacterPrecision(double latitude, double longitude,
 	 * at the same time defines this hash's bounding box.
 	 */
 	public static GeoHash withBitPrecision(double latitude, double longitude, int numberOfBits) {
+		if (numberOfBits < 0) {
+			throw new IllegalArgumentException("A Geohash can't be of negative bits long!");
+		}
 		if (numberOfBits > MAX_BIT_PRECISION) {
 			throw new IllegalArgumentException("A Geohash can only be " + MAX_BIT_PRECISION + " bits long!");
 		}

src/test/java/ch/hsr/geohash/GeoHashTest.java

@@ -116,9 +116,25 @@ private void assertWithin(GeoHash hash, GeoHash bbox) {
 		assertTrue(hash + " should be within " + bbox, hash.within(bbox));
 	}
 
+	@Test
+	public void itShouldCreateAHashWithMinimumPrecisionOf0Bits() {
+		GeoHash geoHash = GeoHash.withBitPrecision(10.0, 10.0, 0);
+		assertEquals(0, geoHash.significantBits());
+		assertEquals(0, geoHash.longValue());
+		assertEquals(new WGS84Point(10.0, 10.0), geoHash.getOriginatingPoint());
+	}
+
 	@Test
 	public void itShouldCreateAHashWithMaximumPrecisionOf64Bits() {
-		GeoHash.withBitPrecision(10.0, 10.0, 64);
+		GeoHash geoHash = GeoHash.withBitPrecision(10.0, 10.0, 64);
+		assertEquals(64, geoHash.significantBits());
+		assertEquals(0xc07e07e07e07e07eL, geoHash.longValue());
+		assertEquals(new WGS84Point(10.0, 10.0), geoHash.getOriginatingPoint());
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void itShouldThrowWhenTheBitPrecisionIsLessThan0Bits() {
+		GeoHash.withBitPrecision(46.0, 8.0, -1);
 	}
 
 	@Test(expected = IllegalArgumentException.class)