如何在java中按两列对csv文件进行排序？_Java_Sorting_Csv

如何在java中按两列对csv文件进行排序？

java sorting csv

如何在java中按两列对csv文件进行排序？,java,sorting,csv,Java,Sorting,Csv,如何按两列对CSV文件进行排序？现在我可以按一列对它进行排序。我需要按前两列对其进行排序。怎么做？下面是我用于按第一列对其进行排序的代码： import java.io.BufferedReader; import java.io.FileReader; import java.io.FileWriter; import java.util.LinkedList; import java.util.List; import java.util.Map; import java.util.Tree

如何按两列对CSV文件进行排序？现在我可以按一列对它进行排序。我需要按前两列对其进行排序。怎么做？下面是我用于按第一列对其进行排序的代码：

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.TreeMap;

public class Practice {
    public static void main(String[] args) throws Exception {
        BufferedReader reader = new BufferedReader(new FileReader("sample-input.csv"));
        Map<String, List<String>> map = new TreeMap<String, List<String>>();
        String line = reader.readLine();//read header
        while ((line = reader.readLine()) != null) {
            String key = getField(line);
            List<String> l = map.get(key);
            if (l == null) {
                l = new LinkedList<String>();
                map.put(key, l);
            }
            l.add(line);
        }

        reader.close();
        FileWriter writer = new FileWriter("output.csv");
        writer.write("Symbol, Exchange, Minimum, Average, Maximum, Total\n");
        for (List<String> list : map.values()) {
            for (String val : list) {
                writer.write(val);
                writer.write("\n");
            }
        }
        writer.close();
    }

    private static String getField(String line) {
        return line.split(",")[0];
        // extract value you want to sort on
    }
}

我需要这样的输出：

ABC,X,0.09,0.11
ABC,X,0.09,0.11
ABC,X,0.09,0.11
ABC,X,0.09,0.11
ABC,X,0.09,0.11
ABC,Y,0.08,0.9
ABC,Y,0.08,0.9
ABC,Z,0.10,0.12
ABC,Z,0.10,0.12
DEF,X,0.14,0.17
DEF,X,0.14,0.17
DEF,Y,0.15,0.17
DEF,Y,0.15,0.17
DEF,Y,0.15,0.17
DEF,Y,0.15,0.17
DEF,Y,0.15,0.17
DEF,Z,0.14,0.15
DEF,Z,0.14,0.15

但是，我希望第三列显示X的最小值，然后是Y的最小值，然后是第三列中当前显示的值中的Z。

尽管创建类作为域的适当表示通常是个好主意：在这种情况下，我不同意这些评论

读取CSV并按一列或多列（字符串的

内容

内容）对其进行排序是一种非常通用的操作。它独立于域

可以实现一个

比较器

，该比较器只需在

列表

的多个索引处选取字符串，并按字典顺序比较这些索引处的值。使用此

比较器

，可以对从CSV文件读取的任何

列表

进行排序

下面是一个简单的例子。它可以用于根据任意列的字符串内容对任何CSV文件进行排序

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class MultiColumnCsvSort
{
    private static final String COLUMN_SEPARATOR = ",";

    public static void main(String[] args) throws Exception
    {
        InputStream inputStream = new FileInputStream("sample-input.csv");
        List<List<String>> lines = readCsv(inputStream);

        // Create a comparator that sorts primarily by column 0,
        // and if these values are equal, by column 2
        Comparator<List<String>> comparator = createComparator(0, 2);
        Collections.sort(lines, comparator);

        OutputStream outputStream = new FileOutputStream("output.csv");
        String header = "Symbol, Exchange, Minimum, Average, Maximum, Total";
        writeCsv(header, lines, outputStream);        
    }

    private static List<List<String>> readCsv(
        InputStream inputStream) throws IOException
    {
        BufferedReader reader = new BufferedReader(
            new InputStreamReader(inputStream));
        List<List<String>> lines = new ArrayList<List<String>>();

        // Skip header
        String line = reader.readLine();

        while (true)
        {
            line = reader.readLine();
            if (line == null)
            {
                break;
            }
            List<String> list = Arrays.asList(line.split(COLUMN_SEPARATOR));
            lines.add(list);
        }
        return lines;
    }

    private static void writeCsv(
        String header, List<List<String>> lines, OutputStream outputStream) 
        throws IOException
    {
        Writer writer = new OutputStreamWriter(outputStream);
        writer.write(header+"\n");
        for (List<String> list : lines)
        {
            for (int i = 0; i < list.size(); i++)
            {
                writer.write(list.get(i));
                if (i < list.size() - 1)
                {
                    writer.write(COLUMN_SEPARATOR);
                }
            }
            writer.write("\n");
        }
        writer.close();

    }

    private static <T extends Comparable<? super T>> Comparator<List<T>> 
        createComparator(int... indices)
    {
        return createComparator(MultiColumnCsvSort.<T>naturalOrder(), indices);
    }

    private static <T extends Comparable<? super T>> Comparator<T>
        naturalOrder()
    {
        return new Comparator<T>()
        {
            @Override
            public int compare(T t0, T t1)
            {
                return t0.compareTo(t1);
            }
        };
    }

    private static <T> Comparator<List<T>> createComparator(
        final Comparator<? super T> delegate, final int... indices)
    {
        return new Comparator<List<T>>()
        {
            @Override
            public int compare(List<T> list0, List<T> list1)
            {
                for (int i = 0; i < indices.length; i++)
                {
                    T element0 = list0.get(indices[i]);
                    T element1 = list1.get(indices[i]);
                    int n = delegate.compare(element0, element1);
                    if (n != 0)
                    {
                        return n;
                    }
                }
                return 0;
            }
        };
    }
}

导入java.io.BufferedReader；
导入java.io.FileInputStream；
导入java.io.FileOutputStream；
导入java.io.IOException；
导入java.io.InputStream；
导入java.io.InputStreamReader；
导入java.io.OutputStream；
导入java.io.OutputStreamWriter；
导入java.io.Writer；
导入java.util.ArrayList；
导入java.util.array；
导入java.util.Collections；
导入java.util.Comparator；
导入java.util.List；
公共类多列CSVSORT
{
私有静态最终字符串列_SEPARATOR=“，”；
公共静态void main（字符串[]args）引发异常
{
InputStream InputStream=新文件InputStream（“sample input.csv”）；
列表行=readCsv（inputStream）；
//创建一个主要按列0排序的比较器，
//如果这些值相等，则按第2列
比较器比较器=创建比较器（0,2）；
集合。排序（行、比较器）；
OutputStream OutputStream=新文件OutputStream（“output.csv”）；
String header=“符号、交换、最小值、平均值、最大值、总计”；
writeCsv（头、行、输出流）；
}
私有静态列表readCsv(
InputStream（InputStream）引发IOException
{
BufferedReader reader=新的BufferedReader(
新的InputStreamReader（inputStream））；
列表行=新的ArrayList（）；
//箕斗式掘进机
字符串行=reader.readLine（）；
while（true）
{
line=reader.readLine（）；
如果（行==null）
{
打破
}
List List=Arrays.asList（line.split（COLUMN_分隔符））；
行。添加（列表）；
}
回流线；
}
私有静态void writeCsv(
字符串标题、列表行、OutputStream（输出流）
抛出IOException
{
Writer Writer=新的OutputStreamWriter（outputStream）；
writer.write（标题+“\n”）；
用于（列表：行）
{
对于（int i=0；iprivate static使用适当的数据表示（即自定义类），列表
和比较器
，用于所需字段（使用集合#排序
）。我同意。您应该明确地将CSV文件解析为表示整体概念（股票报价？）的自定义类实例。很抱歉，我不知道该怎么做。是否读取整个文件，但只写入输出文件中的前两个排序列，并在第三列的单元格中分别写入值？我不确定“*在第三列的单元格中分别写入值*”是什么意思，但是：很容易修改writeCsv
方法来接收一个int
值的列表/数组，这些值指示应该写入哪些列，类似于createComparator
方法中的final int…index
的用法。我可以添加这样一个方法，但类名最初是Practice
，这表明你自己试试这个可能是个好主意，可能会带着更具体的问题回来；-）嗨，Marco13，我编辑了我的问题，更具体地说，是为了让你明白我的确切要求。：）如果我理解正确，你只需添加进一步的排序标准。你可以将我示例中的调用更改为createComparator（0,1,2,3）；根据所有列按字典顺序排序。不不不@Marco13！您不明白。：）我编辑了问题以添加实际需要的输出。第三列仅显示输入表（问题中的第一个表）第2列的最小值当第一列是ABC，第二列是X时，当它是ABC和Y时，则只有输入表第二列的最小值，依此类推。您现在明白了吗(
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class MultiColumnCsvSort
{
    private static final String COLUMN_SEPARATOR = ",";

    public static void main(String[] args) throws Exception
    {
        InputStream inputStream = new FileInputStream("sample-input.csv");
        List<List<String>> lines = readCsv(inputStream);

        // Create a comparator that sorts primarily by column 0,
        // and if these values are equal, by column 2
        Comparator<List<String>> comparator = createComparator(0, 2);
        Collections.sort(lines, comparator);

        OutputStream outputStream = new FileOutputStream("output.csv");
        String header = "Symbol, Exchange, Minimum, Average, Maximum, Total";
        writeCsv(header, lines, outputStream);        
    }

    private static List<List<String>> readCsv(
        InputStream inputStream) throws IOException
    {
        BufferedReader reader = new BufferedReader(
            new InputStreamReader(inputStream));
        List<List<String>> lines = new ArrayList<List<String>>();

        // Skip header
        String line = reader.readLine();

        while (true)
        {
            line = reader.readLine();
            if (line == null)
            {
                break;
            }
            List<String> list = Arrays.asList(line.split(COLUMN_SEPARATOR));
            lines.add(list);
        }
        return lines;
    }

    private static void writeCsv(
        String header, List<List<String>> lines, OutputStream outputStream) 
        throws IOException
    {
        Writer writer = new OutputStreamWriter(outputStream);
        writer.write(header+"\n");
        for (List<String> list : lines)
        {
            for (int i = 0; i < list.size(); i++)
            {
                writer.write(list.get(i));
                if (i < list.size() - 1)
                {
                    writer.write(COLUMN_SEPARATOR);
                }
            }
            writer.write("\n");
        }
        writer.close();

    }

    private static <T extends Comparable<? super T>> Comparator<List<T>> 
        createComparator(int... indices)
    {
        return createComparator(MultiColumnCsvSort.<T>naturalOrder(), indices);
    }

    private static <T extends Comparable<? super T>> Comparator<T>
        naturalOrder()
    {
        return new Comparator<T>()
        {
            @Override
            public int compare(T t0, T t1)
            {
                return t0.compareTo(t1);
            }
        };
    }

    private static <T> Comparator<List<T>> createComparator(
        final Comparator<? super T> delegate, final int... indices)
    {
        return new Comparator<List<T>>()
        {
            @Override
            public int compare(List<T> list0, List<T> list1)
            {
                for (int i = 0; i < indices.length; i++)
                {
                    T element0 = list0.get(indices[i]);
                    T element1 = list1.get(indices[i]);
                    int n = delegate.compare(element0, element1);
                    if (n != 0)
                    {
                        return n;
                    }
                }
                return 0;
            }
        };
    }
}

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class MultiColumnCsvSortExtended
{
    private static final String COLUMN_SEPARATOR = ",";

    public static void main(String[] args) throws Exception
    {
        InputStream inputStream = new FileInputStream("sample-input.csv");
        List<List<String>> lines = readCsv(inputStream);

        // Create a comparator that compares the elements from column 0,
        // in ascending order
        Comparator<List<String>> c0 = createAscendingComparator(0);

        // Create a comparator that compares the elements from column 2,
        // in descending order
        Comparator<List<String>> c1 = createDesendingComparator(2);

        // Create a comparator that compares primarily by using c0,
        // and secondarily by using c1
        Comparator<List<String>> comparator = createComparator(c0, c1);
        Collections.sort(lines, comparator);

        OutputStream outputStream = new FileOutputStream("output.csv");
        String header = "Symbol, Exchange, Minimum, Average";
        writeCsv(header, lines, outputStream);        
    }

    private static List<List<String>> readCsv(
        InputStream inputStream) throws IOException
    {
        BufferedReader reader = new BufferedReader(
            new InputStreamReader(inputStream));
        List<List<String>> lines = new ArrayList<List<String>>();

        String line = null;

        // Skip header
        line = reader.readLine();

        while (true)
        {
            line = reader.readLine();
            if (line == null)
            {
                break;
            }
            List<String> list = Arrays.asList(line.split(COLUMN_SEPARATOR));
            lines.add(list);
        }
        return lines;
    }

    private static void writeCsv(
        String header, List<List<String>> lines, OutputStream outputStream) 
        throws IOException
    {
        Writer writer = new OutputStreamWriter(outputStream);
        writer.write(header+"\n");
        for (List<String> list : lines)
        {
            for (int i = 0; i < list.size(); i++)
            {
                writer.write(list.get(i));
                if (i < list.size() - 1)
                {
                    writer.write(COLUMN_SEPARATOR);
                }
            }
            writer.write("\n");
        }
        writer.close();

    }

    @SafeVarargs
    private static <T> Comparator<T>
        createComparator(Comparator<? super T>... delegates)
    {
        return (t0, t1) -> 
        {
            for (Comparator<? super T> delegate : delegates)
            {
                int n = delegate.compare(t0, t1);
                if (n != 0)
                {
                    return n;
                }
            }
            return 0;
        };
    }

    private static <T extends Comparable<? super T>> Comparator<List<T>>
        createAscendingComparator(int index)
    {
        return createListAtIndexComparator(Comparator.naturalOrder(), index);
    }

    private static <T extends Comparable<? super T>> Comparator<List<T>>
        createDesendingComparator(int index)
    {
        return createListAtIndexComparator(Comparator.reverseOrder(), index);
    }

    private static <T> Comparator<List<T>>
        createListAtIndexComparator(Comparator<? super T> delegate, int index)
    {
        return (list0, list1) -> 
            delegate.compare(list0.get(index), list1.get(index));
    }

}