步骤返回值是接口类型的对象

  private static Connection getConnection(String paramString, Properties paramProperties, ClassLoader paramClassLoader)    throws SQLException  {    synchronized (DriverManager.class)    {      if (paramClassLoader == null)        paramClassLoader = Thread.currentThread().getContextClassLoader();    }    if (paramString == null)      throw new SQLException("The url cannot be null", "08001");    println("DriverManager.getConnection(\"" + paramString + "\")");    ??? = null;    Iterator localIterator = registeredDrivers.iterator();    while (localIterator.hasNext())    {      DriverInfo localDriverInfo = (DriverInfo)localIterator.next();      if (isDriverAllowed(localDriverInfo.driver, paramClassLoader))        try        {          println("    trying " + localDriverInfo.driver.getClass().getName());          Connection localConnection = localDriverInfo.driver.connect(paramString, paramProperties);          if (localConnection != null)          {            println("getConnection returning " + localDriverInfo.driver.getClass().getName());            return localConnection;          }        }        catch (SQLException localSQLException)        {          if (??? == null)            ??? = localSQLException;        }      else        println("    skipping: " + localDriverInfo.getClass().getName());    }    if (??? != null)    {      println("getConnection failed: " + ???);      throw ???;    }    println("getConnection: no suitable driver found for " + paramString);    throw new SQLException("No suitable driver found for " + paramString, "08001");  }