Which two scenarios are NOT safe to replace a StringBuffer object with a StringBuilder object？（） When using versions of Java technology earlier than 5.0.。 When sharing a StringBuffer among multiple threads.。 When using the java.io class StringBufferInputStream.。 When you plan to reuse the StringBuffer to build more than one string.。
Given： What is the result？ （） A new Item object is created with the preferred value in the id attribute.。 The attribute id in the Item object is modified to the new value.。 Compilation fails.。 An exception is thrown at runtime.。 The attribute id in the Item object remains unchanged.。
24″管钳的使用范围是（） 1″～11/2″。 11/2″～2″。 2″～3&Prime。
简述海洋细菌的特性。
A media failure has occurred. This has resulted in all the members of the next log group being rendered inaccessible to the log writer process （LGWR） at a log switch. How does this failure affect the operational database？（） The database allows only queries； no other statements are allowed.。 The database re-creates the missing redo log files automatically.。 The database continues to function normally with the existing files.。 The database returns an error and the database instance shuts down.。 The user sessions that generate redo logs are terminated automatically.。
变压器的二次侧电流增加时，变压器一侧的电流变化情况是（）
