从 HashMap 在 java 中创建 CSV 文件
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Creating a CSV File in java from a HashMap
提问by Red Lion
I have a hashMap in java in terms of some keys which each key is indicating a flow. Then each value showing statics about each packet belongs to that flow.
我在java中有一个hashMap，每个键都表示一个流。然后显示每个数据包的静态数据的每个值都属于该流。
What I need to do is, to draw graphs for each flow based on those values. for example:
我需要做的是，根据这些值为每个流绘制图形。例如：
Flow1: {[length, time],[],[],...}
Flow2: {[length, time],[length, time],[],...}
i need to create a CSV file that then can be read from MS excel. Can anyone has the idea to give me some clues please?
我需要创建一个 CSV 文件，然后可以从 MS excel 中读取该文件。任何人都可以给我一些线索吗？
Edited: here is my hashMap:
编辑：这是我的 hashMap：
Iterator<Flows> iterator = myHashMap.keySet().iterator();
String fileName = ((args.length > 0) ? args[0] : "jexcel.xls");
Map<String, ArrayList> csv = new HashMap<String, ArrayList>();
int i=0;
while(iterator.hasNext()){
Flows key = iterator.next();
ArrayList value = myHashMap.get(key);
csv.put("Flow["+i+"]", value);
}
回答by YoK
You can use from following API's.
您可以使用以下 API。
POI : http://poi.apache.org
兴趣点：http: //poi.apache.org
javacsv : http://sourceforge.net/projects/javacsv
javacsv：http: //sourceforge.net/projects/javacsv
JExcel : http://jexcelapi.sourceforge.net/
JExcel：http://jexcelapi.sourceforge.net/
opencsv : http://opencsv.sourceforge.net/
opencsv：http://opencsv.sourceforge.net/
Following is writting to csv exampleusing supercsv api:
以下是使用 supercsv api写入 csv示例：
import java.io.FileWriter;
import java.util.HashMap;
import org.supercsv.io.*;
import org.supercsv.prefs.CsvPreference;
public class CSVWriteExample {
/**
* @param args
*/
public static void main(String[] args) throws Exception{
ICsvMapWriter writer = new CsvMapWriter(new FileWriter("person.csv"), CsvPreference.EXCEL_PREFERENCE);
try {
final String[] header = new String[] { "name", "city", "pin" };
// set up some data to write
final HashMap<string, ?="" super="" object=""> data1 = new HashMap<string, object="">();
data1.put(header[0], "Raj");
data1.put(header[1], "Vijayawada");
data1.put(header[2], 500026);
final HashMap<string, ?="" super="" object=""> data2 = new HashMap<string, object="">();
data2.put(header[0], "Suneel");
data2.put(header[1], "Tenali");
data2.put(header[2], 522202);
// the actual writing
writer.writeHeader(header);
writer.write(data1, header);
writer.write(data2, header);
System.out.println("Writing Completed...!");
} finally {
writer.close();
}
}
}
Also realted questions on stackoverflow can be found :
还可以找到有关 stackoverflow 的相关问题：
Can you recommend a Java library for reading (and possibly writing) CSV files?
回答by duffymo
If you really want an Excel file, the best library for creating one is Andy Khan's JExcel.
如果您真的想要一个 Excel 文件，那么创建 Excel 文件的最佳库是Andy Khan 的 JExcel。
I think you'd need one worksheet per flow, with .csv pairs for each one, sorted by time.
我认为每个流程需要一个工作表，每个工作表都有 .csv 对，按时间排序。
If these are graphs of a variable versus time, wouldn't "time" be the first value in each pair?
如果这些是变量与时间的关系图，“时间”不是每对中的第一个值吗？
Here's how I'd do it. It works perfectly for the simple test case I supplied - it's working code that you'll be able to extend.
这就是我要怎么做。它非常适合我提供的简单测试用例 - 它是您可以扩展的工作代码。
package jexcel;
import jxl.Workbook;
import jxl.write.WritableSheet;
import jxl.write.WritableWorkbook;
import jxl.write.WriteException;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class JExcelUtils
{
public static void main(String[] args)
{
String fileName = ((args.length > 0) ? args[0] : "jexcel.xls");
Map<String, List<Pair>> csv = new HashMap<String, List<Pair>>()
{{
put("Flow1", fromArrayToList(new double[][]
{
{ 0.0, 0.0 },
{ 0.1, 1.0 },
{ 0.2, 2.0 },
{ 0.3, 3.0 },
{ 0.4, 4.0 },
{ 0.5, 5.0 },
}));
put("Flow2", fromArrayToList(new double[][]
{
{ 0.0, 0.0 },
{ 0.1, 1.0 },
{ 0.2, 4.0 },
{ 0.3, 9.0 },
{ 0.4, 16.0 },
{ 0.5, 25.0 },
}));
}};
WritableWorkbook excelContents = null;
try
{
File excelFile = new File(fileName);
excelContents = createExcel(excelFile, csv);
excelContents.write();
}
catch (IOException e)
{
e.printStackTrace();
}
catch (WriteException e)
{
e.printStackTrace();
}
finally
{
try { if (excelContents != null) excelContents.close(); } catch (Exception e) { e.printStackTrace(); }
}
}
public static List<Pair> fromArrayToList(double [][] input)
{
List<Pair> result = new ArrayList<Pair>();
for (int i = 0; i < input.length; ++i)
{
result.add(new Pair(input[i][0], input[i][1]));
}
return result;
}
public static WritableWorkbook createExcel(File excelFile, Map<String, List<Pair>> worksheets) throws IOException, WriteException
{
WritableWorkbook result = Workbook.createWorkbook(excelFile);
int order = 0;
for (String worksheetName : worksheets.keySet())
{
WritableSheet worksheet = result.createSheet(worksheetName, order++);
List<Pair> worksheetValues = worksheets.get(worksheetName);
for (int row = 0; row < worksheetValues.size(); ++row)
{
worksheet.addCell(new jxl.write.Number(0, row, worksheetValues.get(row).getX()));
worksheet.addCell(new jxl.write.Number(1, row, worksheetValues.get(row).getY()));
}
}
return result;
}
}
class Pair
{
private double x;
private double y;
Pair(double x, double y)
{
this.x = x;
this.y = y;
}
public double getX()
{
return x;
}
public double getY()
{
return y;
}
}
