java读取写入CSV文件

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读取CSV文件中的数据示例一

• 示例一为读取一个N行Dim列的逗号分隔的二维Double类型csv文件
• 基本思路
• 按行读取，每一行都是一个String,使用Split函数分成一个String[],将String[]中每个元素转为Double类型存入Double[]数组中，每一行的Double[]在存入ArrayList中。
  

public void test() {
    readValues(OutputfilePath, Valueslist);
    for (int i = 0; i < Valueslist.size(); i++) {
        for (int j = 0; j <Valueslist.get(0).length; j++) {
            System.out.print(Valueslist.get(i)[j]+"  ");
        }
        System.out.println();
    }
}

public void readValues(String readpath, ArrayList<Double[]> Valueslist) {
    //想要读取的数据是一个[N,Dim]的二维矩阵
    File inFile = new File(readpath);
    try {
        BufferedReader reader = new BufferedReader(new FileReader(inFile));

        while (reader.ready()) {
            //这里没有办法使用矩阵进行操作，因为我们一行一行的读没有办法知道csv中保存数据的长度和宽度
            //但是返回的是一个String，我们可以对这个String进行操作，按照分隔符将其分割，最好能是能够保存到一个完整的结构中
            String line = reader.readLine();
            String[] splitline = line.split(",");
            //这里每一列的元素都是一个double数值，例如
            //因此接下来我能够直接的转换成Double类型的变量
            int Dim = splitline.length;
            //将splitline中的每个元素保存到double类型的数组中
            Double[] temp = new Double[Dim];
            for (int i = 0; i < Dim; i++) {
                temp[i] = Double.valueOf(splitline[i]);
            }
            Valueslist.add(temp);
        }
        reader.close();

    } catch (Exception e) {
        e.printStackTrace();
    }
}

读取CSV文件中的数据示例二

• 示例二维读取一个N行两列的逗号分隔的二维数字字符串混合的csv文件
  

import java.io.*;
import java.util.ArrayList;
import java.util.StringTokenizer;

public class readCSV {
    void readCSV(String readpath, ArrayList Nolist, ArrayList Dnalist) {
        File inFile = new File(readpath);
        try {
            BufferedReader reader = new BufferedReader(new FileReader(inFile));
            //判断是否到达文件末尾
            while (reader.ready()) {
                String line = reader.readLine();
                //返回一个","分隔的迭代器
                //这种方法不是很好，建议还是使用示例一中的方法
                StringTokenizer st = new StringTokenizer(line, ",");
                int NO;
                String DNAsequence;

                if (st.hasMoreTokens()) {
                    NO = Integer.valueOf(st.nextToken().trim());
                    DNAsequence = String.valueOf(st.nextToken().trim());
                    //使用ArrayList接收数据
                    Nolist.add(NO);
                    Dnalist.add(DNAsequence);
                }
            }
            reader.close();

        } catch (Exception e) {

            e.printStackTrace();
        }
    }
}

将数据保存为csv格式

package Readcsv_testV0;
import java.io.*;
import java.util.ArrayList;

public class OutputCSV {
    public static void writeCSV(ArrayList<String []> DNA, ArrayList<Double> Con, ArrayList<Double> Hp, ArrayList<Double> Hm, ArrayList<Double> Si, ArrayList<Double> Tm, ArrayList<Double> GC, String path) {
        try {
            BufferedWriter out = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(path), "UTF-8"));
            for (int i = 0; i < DNA.size(); i++) {
                out.write(DNA.get(i)[0]);
                out.write(",");
                out.write(DNA.get(i)[1]);
                out.write(",");
                out.write(Con.get(i).toString());
                out.write(",");
                out.write(Hp.get(i).toString());
                out.write(",");
                out.write(Hm.get(i).toString());
                out.write(",");
                out.write(Si.get(i).toString());
                out.write(",");
                out.write(Tm.get(i).toString());
                out.write(",");
                out.write(GC.get(i).toString());
                out.newLine();
            }
            out.flush();
            out.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }
}