?? 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(yǔ)言的一個(gè)特征，對(duì)于每個(gè)元素類型T，都有數(shù)組類型T[];然而，ArrayList類是個(gè)定義java.util包中的類庫(kù)。這是一個(gè)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(shí)，需要進(jìn)行類型轉(zhuǎn)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(gè)Object引用的內(nèi)部數(shù)組。最終，可能會(huì)用完數(shù)組的空間。如果調(diào)用了add，而內(nèi)部數(shù)組已經(jīng)滿了，數(shù)組列表將自動(dòng)創(chuàng)建了一個(gè)更大的數(shù)組，并自動(dòng)把小數(shù)組中的對(duì)象拷貝到大數(shù)組中
? Size方法返回?cái)?shù)組列表的實(shí)際元素個(gè)數(shù)
??? staff.size()??? 它等價(jià)于數(shù)組a的a.length???
???訪問(wèn)數(shù)組列表元素
因?yàn)?ArrayList類不是Java語(yǔ)言的一部分，它只是個(gè)提供在標(biāo)準(zhǔn)庫(kù)中、由某人編寫的工具類，并不像在訪問(wèn)數(shù)組元素時(shí)可以使用[]語(yǔ)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(shè)置第i個(gè)元素，需要使用：
?? staff.set(i,harry);
得到數(shù)組列表元素要更復(fù)雜一些，因?yàn)間et方法返回的類型是Object，你還需要把它轉(zhuǎn)換為想要的類型
?? Employee e = (Employee)staff.get(i); 它等價(jià)于Employee e = a[i];

?? 最后總結(jié)一下：
?無(wú)需指定數(shù)組大小
用add增添任意多的元素;
用size()代替length計(jì)算元素的個(gè)數(shù);
用(Employee)a.get(i)代替a[i]訪問(wèn)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(jìn)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;
????}

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