private int hash; // Default to 0 public int hashCode() { int h = hash; if (h == 0 && value.length > 0) { char val[] = value; for (int i = 0; i < value.length; i++) { h = 31 * h + val[i]; } hash = h; } return h; }
原文：http://www.cnblogs.com/go4mi/p/7064229.html