+public final class HashCodeBuilder<T> {
+ /**
+ * The value 31 was chosen because it is an odd prime. If it were even and the multiplication overflowed,
+ * information would be lost, as multiplication by 2 is equivalent to shifting. The advantage of using a prime is
+ * less clear, but it is traditional. A nice property of 31 is that the multiplication can be replaced by a shift
+ * and a subtraction for better performance: 31 * i == (i << 5) - i. Modern VMs do this sort of optimization
+ * automatically.
+ *
+ * <p>(from Joshua Bloch's Effective Java, Chapter 3, Item 9: Always override hashcode when you override equals,
+ * page 48)
+ */
+ private static final int PRIME = 31;