java.util.ArrayList

Wed, 14 Mar 2007 01:14:00 GMT

€ �?数组和数�l�列表之间有着重大的区别。数�l�是Java语言的一个特征，对于每个元素�c�d��T�Q�都有数�l�类型T[];然而，ArrayList�c�L��个定义java.util包中的类库。这是一个存放object�c�d��元素�?普通�?的类型。要注意的是�Q�要从数�l�列表中提取元素�Ӟ��需要进行类型�{换�?br /> 使用add�Ҏ(gu��)��可以向数�l�列表中��d��新元素：(x��)
   ArrayList staff = new ArrayList();
   staff.add(new Employee(....));
   staff.add(new Employee(....));
   ArrayList�cȝ��理了一个Object引用的内部数�l�。最�l�，可能�?x��)用完数�l�的�I�间。如果调用了add�Q�而内部数�l�已�l�满了，数组列表��自动创��Z��一个更大的数组�Q��ƈ自动把小数组中的对象拯��到大数组�?br /> Size�Ҏ(gu��)��q�回数组列表的实际元素个�?br />    staff.size()    它等价于数组a的a.length
   讉K��数组列表元素
因�ؓ(f��) ArrayList�c�M��是Java语言的一部分�Q�它只是个提供在标准库中、由某�h�~�写的工��L(f��ng)��Q��ƈ不像在访问数�l�元素时可以使用[]语法那样�Q�要存取或改变数�l�元素，你必��M��用get和set�Ҏ(gu��)��
   要设�|�第i个元素，需要��用：(x��)
   staff.set(i,harry);
得到数组列表元素要更复杂一些，因�ؓ(f��)get�Ҏ(gu��)��q�回的类型是Object�Q�你�q�需要把它�{换�ؓ(f��)惌��的类�?br />   Employee e = (Employee)staff.get(i); 它等价于Employee e = a[i];

   最后�ȝ��一下：(x��)
无需指定数组大小
用add增添��L��多的元素;
用size()代替length计算元素的个�?
�?Employee)a.get(i)代替a[i]讉K��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();//��得到的“文件名“进行封�?br />                            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;
    }

��d��arraylist里的�?

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

张小�?/a> 2007-03-14 09:14 发表评论

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java.util.ArrayList