€?? 數(shù)組和數(shù)組列表之間有著重大的區(qū)別。數(shù)組是Java語言的一個特征，對于每個元素類型T，都有數(shù)組類型T[];然而，ArrayList類是個定義java.util包中的類庫。這是一個存放object類型元素的"普通性"的類型。要注意的是，要從數(shù)組列表中提取元素時，需要進行類型轉換。
? 使用add方法可以向數(shù)組列表中添加新元素：
?? ArrayList staff = new ArrayList();
?? staff.add(new Employee(....));
?? staff.add(new Employee(....));
?? ArrayList類管理了一個Object引用的內部數(shù)組。最終，可能會用完數(shù)組的空間。如果調用了add，而內部數(shù)組已經(jīng)滿了，數(shù)組列表將自動創(chuàng)建了一個更大的數(shù)組，并自動把小數(shù)組中的對象拷貝到大數(shù)組中
? Size方法返回數(shù)組列表的實際元素個數(shù)
??? staff.size()??? 它等價于數(shù)組a的a.length???
???訪問數(shù)組列表元素
因為 ArrayList類不是Java語言的一部分，它只是個提供在標準庫中、由某人編寫的工具類，并不像在訪問數(shù)組元素時可以使用[]語法那樣，要存取或改變數(shù)組元素，你必須使用get和set方法
?? 要設置第i個元素，需要使用：
?? staff.set(i,harry);
得到數(shù)組列表元素要更復雜一些，因為get方法返回的類型是Object，你還需要把它轉換為想要的類型
?? Employee e = (Employee)staff.get(i); 它等價于Employee e = a[i];

?? 最后總結一下：
?無需指定數(shù)組大小
用add增添任意多的元素;
用size()代替length計算元素的個數(shù);
用(Employee)a.get(i)代替a[i]訪問元素i;

public ?Collection?setRollBack(QueueVB?job)? throws ?CustomException
???? {
????????
????????String?sqlselect? = ? " select?FileName?from?JobQueue?where?BatchNum= " + job.getBatchNum() + " ?and?DocTypeID= " + job.getDocTypeID() + " and?JobState='6' " ;
????????String?sql? = ? " update?JobQueue?set?JobState= " + JobState.SAVE + " ?where?BatchNum= " + job.getBatchNum() + " ?and?DocTypeID= " + job.getDocTypeID() + " ?and?JobNum= " + job.getJobNum() + "" ;
????????ArrayList?array = new ?ArrayList();
????????System.out.println(sql);
???????????????? try
???????????????? {
????????????????????getConnection = ConnectionLocator.getInstance().getConnection(strJNDI);
????????????????????ResultSet?rs = null ;
???????????????????? if (getConnection != null )
???????????????????? {
????????????????????????PreparedStatement?pstmt1 = getConnection.prepareStatement(sqlselect);
????????????????????????PreparedStatement?pstmt = getConnection.prepareStatement(sql);
????????????????????????
????????????????????????rs? = ?pstmt1.executeQuery();
????????????????????????pstmt.executeUpdate();
???????????????????????? while (rs.next())
???????????????????????? {
????????????????????????????String?fileName? = ?rs.getString( " FileName " );
????????????????????????????FileNameVB?filenameVB? = ? new ?FileNameVB();//將得到的“文件名“進行封裝
????????????????????????????filenameVB.setFileName(fileName);
????????????????????????????array.add(filenameVB);
????????????????????????}
???????????????????????? try
???????????????????????? {
????????????????????????????pstmt.close();
????????????????????????}
???????????????????????? catch (SQLException?e)
???????????????????????? { throw ? new ?CustomException(e.getMessage(), " exs " );}
???????????????????????? try
???????????????????????? {
????????????????????????????getConnection.close();
????????????????????????}
???????????????????????? catch (SQLException?e)
???????????????????????? { throw ? new ?CustomException(e.getMessage(), " exs " );}
????????????????????}
????????????????}
???????????????? catch (SQLException?e)
???????????????? { throw ? new ?CustomException(e.getMessage(), " ex00050 " );}
???????????????? return ?array;
????}

讀取arraylist里的值

Collection?m?? = ?inputFacade.setRollBack(job);
????????????????????ArrayList?array? = ?(ArrayList)m;
???????????????????? for ( int ?i = 0 ;i < array.size();i ++ )
???????????????????? {???
????????????????????????filenameVB? = ?(FileNameVB)array.get(i);