### Question:
HintManagerHolder { public static void setHintManager(final HintManager hintManager) { Preconditions.checkState(null == HINT_MANAGER_HOLDER.get(), "HintManagerHolder has previous value, please clear first."); HINT_MANAGER_HOLDER.set(hintManager); }  static void setHintManager(final HintManager hintManager); static boolean isUseShardingHint(); static Optional<ShardingValue<?>> getDatabaseShardingValue(final ShardingKey shardingKey); static Optional<ShardingValue<?>> getTableShardingValue(final ShardingKey shardingKey); static boolean isMasterRouteOnly(); static boolean isDatabaseShardingOnly(); static void clear(); static final String DB_TABLE_NAME; static final String DB_COLUMN_NAME; }### Answer:
@Test(expected = IllegalStateException.class) public void assertSetHintManagerTwice() { HintManagerHolder.setHintManager(HintManager.getInstance()); }