1.public static boolean equals(Object a, Object b)
2. public static int hashCode(Object o)
null argument and 0 for a null argument.3.public static int hash(Object... values)
Arrays.hashCode(Object[]).4.public static <T> int compare(T a, T b, Comparator<? super T> c)
5.public static <T> T requireNonNull(T obj)
原文：http://www.cnblogs.com/fengfengtk/p/5941698.html