从文本中读取指定的列插到另一个文本

问题：如果一个文本中有如下内容
 a b c d .....e.....
 a1 b1 c1 d1 .....e1.....
 a2 b2 c2 d2 .....e2.....
 a3 b3 c3 d3 .....e3.....
 a4 b4 c4 d4 .....e4.....
 a5 b5 c5 d5 .....e5.....
 a6 b6 c6 d6 .....e6.....
 a7 b7 c7 d7 .....e7.....
 a8 b8 c8 d8 .....e8.....
 a9 b9 c9 d9 .....e9.....

要求给你a,d两列，如何把文本中对应的a,d两列输入到另一个文本中，变成如下所示？
 a d
 a1,d1
 a2,d2
 a3,d3
 a4,d4
 a5,d5
 a6,d6
 a7,d7
 a8,d8
 a9,d9

第一种方法：先查找并记录要求列在文本中对应的下标，再输出文本对应下标列：

public static void main(String[] args) throws Exception {
        File file = new File("E:\\WorkSpace\\Test\\TxtReaderTest1.txt");
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(new File("E:\\WorkSpace\\Test\\TxtReaderTest1W.txt")),"UTF-8"));
        BufferedInputStream inputStream = new BufferedInputStream(new FileInputStream(file));//将文件转成字节流
        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream),5*1024*1024);//将转好的字节流转成字符流
        BufferedReader systemRead = new BufferedReader(new InputStreamReader(System.in));//用户输入数据流
        try {
            String line = null;//原文本中的每一行
            List strs1 = new ArrayList();//用户输入的要读的列标签
            int num[] = null;//每个列标签的位置
            /**
             * 第一步：记录下要读的标签，以及它的下标位置
             */
            if((line = reader.readLine()) != null) {//读取第一列
                String[] infoArraay = line.split(" ");//根据空格分割第一列进数组
                System.out.println("请从以下数组任选几个列,最多输入"+infoArraay.length+"个");
                System.out.println(Arrays.toString(infoArraay));
                for (int i = 0;i < infoArraay.length;i++) {
                    System.out.println("请输入，输入好列后请输入OK：");
                    String input = systemRead.readLine();
                    if ("OK".equals(input)) {
                        break;
                    }
                    if (Arrays.asList(infoArraay).contains(input)) {
                        strs1.add(input);
                        continue;
                    }
                    System.out.println("不包含");
                }
                num = new int[strs1.size()];//每个标签的位置
                //看要求读的标签各在哪个下标，记录下来
                for (int i = 0; i < strs1.size(); i++) {//用户输入的数组组
                    for (int j = 0; j < infoArraay.length; j++) {//需要对照的文本的第一列首
                        if(infoArraay[j].equals(strs1.get(i))) {
                            num[i] = j;
                            writer.write(infoArraay[j]+" ");
                            break;
                        }
                    }
                }
                writer.newLine();//换行
            }
            /**
             * 第二步：通过已记录的下标位置，逐行获取对应的列并拼好，放入writer对象
             */
            while((line = reader.readLine()) != null) {//逐行的读
                //将读取到的行进行分割进数组
                String[] infoArraay = line.split(" ");
                String str = "";
                //根据已记录的下标获取数组里的值，进行拼接字符串
                for (int i = 0; i < num.length; i++) {
                    str += infoArraay[num[i]]+",";
                }
                str = str.substring(0, str.length()-1);//保持完整性，去掉符号“,”
                writer.write(str);//写入一行
                writer.newLine();//换行
            }
        } catch (Exception e) {
            System.out.println("毁灭吧，赶紧的");
            e.printStackTrace();
        } finally {
            systemRead.close();
            reader.close();
            writer.close();
        }
    }

第二种方法：通过正则表达式匹配：

public static void main(String[] args) throws IOException {
        File fileR = new File("E:\\WorkSpace\\Test\\PatternMatcherReadTest.txt");
        File fileW = new File("E:\\WorkSpace\\Test\\PatternMatcherReadTestW.txt");
        BufferedReader br = new BufferedReader(new FileReader(fileR));
        BufferedWriter bw = new BufferedWriter(new FileWriter(fileW ));
        try {
            String s;
            String[] ss = {"a","d"};
            Pattern p =null;
            while( (s = br.readLine() ) != null){
                System.out.println(s);
                String str="";
                for (int i = 0 ; i<ss.length;i++){
                    p = Pattern.compile(ss[i]+".");
                    Matcher m = p.matcher(s);
                    if (m.find() ){
                        str += m.group(0)+",";
                    }
                }
                str = str.substring(0, str.length()-1);//末尾去掉符号“,”  保持每一行输出的完整性
                bw.write(str);
                bw.newLine();//换行
                bw.flush();
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            br.close();
            bw.close();
            fileR.exists();
            fileW.exists();

        }

    }