fix upper bound of Xorshf32b

Author: TilmanNeumann

src/main/java/de/tilman_neumann/jml/random/Xorshf32b.java

@@ -44,9 +44,8 @@ public int nextInt() {
 	 * @return a random int number N with 0 <= N <= max.
 	 */
 	public int nextInt(int max) {
-		final long i = nextInt();
-		final long l = i<0 ? -i : i;  // up to unsigned 2^31 - 1
-		final long prod = l * max; // up to max * (2^31 - 1)
+		final long l = nextInt() & 0xFFFFFFFFL; // take it as unsigned
+		final long prod = l * max;
 	    return (int) (prod >>> 32);
 	}
 

src/test/java/de/tilman_neumann/jml/random/Xorshf32bTest.java

@@ -80,7 +80,7 @@ public void testNextIntLowerUpperBound() {
 			if (n>max) max = n;
 		}
 		LOG.debug(NCOUNT + " numbers from " + rng.getClass().getSimpleName() + ".nextInt(" + LOWER + ", " + UPPER + ") gave min = " + min + ", max = " + max);
-		assertTrue(min >= LOWER);
-		assertTrue(max <= UPPER);
+		assertTrue("Expected " + min + " >= " + LOWER, min >= LOWER);
+		assertTrue("Expected " + max + " <= " + UPPER, max <= UPPER);
 	}
 }