我编写了大量代码，这些代码从url下载CSV文件，然后将其批量插入sql数据库，然后从SQL Server调用数据并在Java控制台上显示。最后，选择我要保留的列并导出为新的CSV文件。但是所有这些代码现在都在同一个类中。我如何将它们分成不同的类，例如我希望一个类仅用于下载文件，另一个类仅执行批量插入，另一个类仅执行选择查询。谢谢你的协助下面是我现在在一类中的代码
public class ProjectTest extends CreateTable {
public static void main(String[] args) throws MalformedURLException {
BufferedReader br = null;
String line = "";
String cvsSplitBy = ",";
URL url = new URL(
"https://quality.data.gov.tw/dq_download_csv.php?nid=43983&md5_url=9d38afbca8243a24b5b89d03a8070aff");
try (InputStream inputStream = url.openStream();
FileOutputStream fos = new FileOutputStream(
"C:\\Users\\ALICE\\Desktop\\Java\\Dropbox\\Java\\virus.csv");
Connection connection = DriverManager
.getConnection("jdbc:sqlserver://localhost:1433;databaseName=JDBCDB", "andy3", "andy"); // andy3
// //
// ,andy
Statement stmt = connection.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,
ResultSet.CONCUR_UPDATABLE);
FileOutputStream fos2 = new FileOutputStream(
"C:\\Users\\ALICE\\Desktop\\Java\\Dropbox\\Java\\NEWvirus.csv");
OutputStreamWriter osw = new OutputStreamWriter(fos2, "MS950");
BufferedWriter bw = new BufferedWriter(osw);
) {
byte[] buffer = new byte[1024];
int length;
while ((length = inputStream.read(buffer)) != -1) {
fos.write(buffer, 0, length);
}
fos.close();
stmt.executeUpdate("DROP TABLE Virus");
boolean rs = stmt.execute(CreateTable);
System.out.println("Database Created");
PreparedStatement pstmt = connection.prepareStatement(InsertData);
int executeUpdate = pstmt.executeUpdate();
if (executeUpdate > 0) {
System.out.println("Data Inserted");
} else {
System.out.println("Insert ERROR");
}
ResultSet rs4 = stmt.executeQuery("SELECT Count(*) FROM Virus");
int numberOfData = rs4.getInt(1);
System.out.println(numberOfData);
ResultSet rs3 = stmt.executeQuery(selectQuery);
ResultSetMetaData metaData = rs3.getMetaData();
DatabaseMetaData DmetaData = connection.getMetaData();
String[] types = { "TABLE" };
ResultSet rs5 = DmetaData.getTables(null, null, "Virus", types);
List<String> ColNameList = new ArrayList<String>();
while (rs5.next()) {
String tableName = rs5.getString("TABLE_NAME");
ResultSet columnRs = DmetaData.getColumns(null, null, tableName, null);
while (columnRs.next()) {
String columnName = columnRs.getString("COLUMN_NAME");
ColNameList.add(columnName);
}
System.out.print("|" + ColNameList.get(0) + " |");
System.out.print(ColNameList.get(1) + " |");
System.out.print(ColNameList.get(2) + "|");
System.out.print(ColNameList.get(3) + "|");
System.out.print(ColNameList.get(4) + " |");
System.out.print(ColNameList.get(5) + " |");
System.out.print(ColNameList.get(6) + " |");
System.out.print(ColNameList.get(7) + " |");
System.out.print(ColNameList.get(8) + "|");
System.out.print(ColNameList.get(9) + " |");
System.out.print(ColNameList.get(10) + " |");
System.out.print(ColNameList.get(11) + "|");
System.out.print(ColNameList.get(12) + " |");
System.out.print(ColNameList.get(13) + " |");
System.out.print(ColNameList.get(14) + " |");
System.out.print(ColNameList.get(15) + "");
}
System.out.println();
while (rs3.next()) {
coList1.add(rs3.getString(1));
coList2.add(rs3.getString(2));
coList3.add(rs3.getString(3));
coList4.add(rs3.getString(4));
coList5.add(rs3.getString(5));
coList6.add(rs3.getString(6));
coList7.add(rs3.getString(7));
coList8.add(rs3.getString(8));
coList9.add(rs3.getString(9));
coList10.add(rs3.getString(10));
coList11.add(rs3.getString(11));
coList12.add(rs3.getString(12));
coList13.add(rs3.getString(13));
coList14.add(rs3.getString(14));
coList15.add(rs3.getString(15));
coList16.add(rs3.getString(16));
coList17.add(rs3.getString(17));
}
for (int p = 0; p < 20; p++) { // coList9.size(
System.out.print("|" + coList1.get(p) + "|");
String str2 = coList2.get(p);
if (str2.length() < 3) {
String blank = " ";
String repeated = new String(new char[(3 - str2.length())]).replace("\0", blank);
System.out.print(repeated + coList2.get(p) + "|");
} else {
System.out.print(coList2.get(p) + "|");
}
System.out.print(" " + coList3.get(p) + "|");
System.out.print(coList4.get(p) + "|");
System.out.print(coList5.get(p) + "|");
System.out.print(coList6.get(p) + "|");
System.out.print(coList7.get(p) + "|");
System.out.print(coList8.get(p) + "|");
String str = coList9.get(p);
if (str.length() < 5) {
String blank = " ";
String repeated = new String(new char[(5 - str.length())]).replace("\0", blank);
System.out.print(repeated + coList9.get(p) + "|");
} else {
System.out.print(coList9.get(p) + "|");
}
System.out.print(coList10.get(p) + "|");
System.out.print(coList11.get(p) + "|");
String str12 = coList12.get(p);
if (str12.length() < 5) {
String blank = " ";
String repeated = new String(new char[(6 - str12.length())]).replace("\0", blank);
System.out.print(repeated + coList12.get(p) + "|");
} else {
System.out.print(coList12.get(p) + "|");
}
String str13 = coList13.get(p);
if (str13.length() < 5) {
String blank = " ";
String repeated = new String(new char[(4 - str13.length())]).replace("\0", blank);
System.out.print(repeated + coList13.get(p) + "|");
} else {
System.out.print(coList12.get(p) + "|");
}
System.out.print(coList14.get(p) + "|");
System.out.print(coList15.get(p) + "|");
System.out.print(coList16.get(p) + "|");
System.out.print(coList17.get(p) + "|");
System.out.println();
}
rs3.beforeFirst();
StringBuilder builder = new StringBuilder();
builder.append("CaseID").append(",").append("Age").append(",").append("Gender").append(",").append("City")
.append(",").append("SampleDate").append(",").append("VirusType").append(",")
.append("SubType").append(",").append("Locus").append(",").append("Primer").append(",").append("GeneDirection")
.append(",").append("TypingMethod").append(",").append("DNASeq").append(",").append("AminoAcidSeq");
System.out.println(rs3.next());
while (rs3.next()) {
builder.append(System.lineSeparator());
builder.append(rs3.getString(1)).append(",").append(rs3.getString(2)).append(",")
.append(rs3.getString(3)).append(",").append(rs3.getString(5)).append(",")
.append(rs3.getString(7)).append(",").append(rs3.getString(10)).append(",")
.append(rs3.getString(11)).append(",").append(rs3.getString(12)).append(",")
.append(rs3.getString(13)).append(",").append(rs3.getString(14)).append(",")
.append(rs3.getString(15)).append(",").append(rs3.getString(16)).append(",").append(rs3.getString(17)).append(",");
}
bw.write(builder.toString());
} catch (IOException e) {
e.printStackTrace();
} catch (SQLException e1) {
e1.printStackTrace();
}
}
}
以小步骤开始重构代码，然后根据需要迭代地改进设计。
正如您提到的算法方法一样，充分利用这应该作为您的开始步骤。
每个步骤的小助手功能。如果有助于改善您的解决方案，请阅读有关SOLID设计原则的更多信息。