将CSV文件合并到单个文件中，没有重复的标题
我有一些具有相同列标题的CSV文件。 例如
档案A.
header1,header2,header3 one,two,three four,five,six 档案B.
header1,header2,header3 seven,eight,nine ten,eleven,twelve
我想合并它，以便将数据合并到一个文件中，标题位于顶部，但在其他地方没有标题。
header1,header2,header3 one,two,three four,five,six seven,eight,nine ten,eleven,twelve
实现这一目标的好方法是什么？
这应该工作。 它检查正在合并的文件是否具有匹配的标头。 否则会抛出exception。 exception处理（关闭流等）已被留作练习。
String[] headers = null; String firstFile = "/path/to/firstFile.dat"; Scanner scanner = new Scanner(new File(firstFile)); if (scanner.hasNextLine()) headers[] = scanner.nextLine().split(","); scanner.close(); Iterator iterFiles = listOfFilesToBeMerged.iterator(); BufferedWriter writer = new BufferedWriter(new FileWriter(firstFile, true)); while (iterFiles.hasNext()) { File nextFile = iterFiles.next(); BufferedReader reader = new BufferedReader(new FileReader(nextFile)); String line = null; String[] firstLine = null; if ((line = reader.readLine()) != null) firstLine = line.split(","); if (!Arrays.equals (headers, firstLine)) throw new FileMergeException("Header mis-match between CSV files: '" + firstFile + "' and '" + nextFile.getAbsolutePath()); while ((line = reader.readLine()) != null) { writer.write(line); writer.newLine(); } reader.close(); } writer.close();
这是一个例子：
public static void main(String[] args) throws IOException { List paths = Arrays.asList(Paths.get("c:/temp/file1.csv"), Paths.get("c:/temp/file2.csv")); List mergedLines = getMergedLines(paths); Path target = Paths.get("c:/temp/merged.csv"); Files.write(target, mergedLines, Charset.forName("UTF-8")); } private static List getMergedLines(List paths) throws IOException { List mergedLines = new ArrayList<> (); for (Path p : paths){ List lines = Files.readAllLines(p, Charset.forName("UTF-8")); if (!lines.isEmpty()) { if (mergedLines.isEmpty()) { mergedLines.add(lines.get(0)); //add header only once } mergedLines.addAll(lines.subList(1, lines.size())); } } return mergedLines; }
在Java中做这个似乎有点重量级。 它在Linux shell中很简单：
(cat FileA ; tail --lines=+2 FileB) > FileC
之前：
idFile＃x_y.csv
后：
idFile.csv
例如：
100＃1_2.csv + 100＃2_2.csv> 100.csv
100＃1_2.csv包含：
"one","two","three" "a","b","c" "d","e","f"
100＃2_2.csv包含：
"one","two","three" "g","h","i" "j","k","l"
100.csv包含：
"one","two","three" "a","b","c" "d","e","f" "g","h","i" "j","k","l"
资源：
//MergeDemo.java import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.File; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.util.ArrayList; //import java.util.Arrays; import java.util.Iterator; import java.util.Scanner; public class MergeDemo { public static void main(String[] args) { String idFile = "100"; int numFiles = 3; try { mergeCsvFiles(idFile, numFiles); } catch (IOException e) { e.printStackTrace(); } } private static void mergeCsvFiles(String idFile, int numFiles) throws IOException { // Variables ArrayList files = new ArrayList (); Iterator iterFiles; File fileOutput; BufferedWriter fileWriter; BufferedReader fileReader; String csvFile; String csvFinal = "C:\\out\\" + idFile + ".csv"; String[] headers = null; String header = null; // Files: Input for (int i = 1; i <= numFiles; i++) { csvFile = "C:\\in\\" + idFile + "#" + i + "_" + numFiles + ".csv"; files.add(new File(csvFile)); } // Files: Output fileOutput = new File(csvFinal); if (fileOutput.exists()) { fileOutput.delete(); } try { fileOutput.createNewFile(); // log // System.out.println("Output: " + fileOutput); } catch (IOException e) { // log } iterFiles = files.iterator(); fileWriter = new BufferedWriter(new FileWriter(csvFinal, true)); // Headers Scanner scanner = new Scanner(files.get(0)); if (scanner.hasNextLine()) header = scanner.nextLine(); // if (scanner.hasNextLine()) headers = scanner.nextLine().split(";"); scanner.close(); /* * System.out.println(header); for(String s: headers){ * fileWriter.write(s); System.out.println(s); } */ fileWriter.write(header); fileWriter.newLine(); while (iterFiles.hasNext()) { String line;// = null; String[] firstLine;// = null; File nextFile = iterFiles.next(); fileReader = new BufferedReader(new FileReader(nextFile)); if ((line = fileReader.readLine()) != null) firstLine = line.split(";"); while ((line = fileReader.readLine()) != null) { fileWriter.write(line); fileWriter.newLine(); } fileReader.close(); } fileWriter.close(); } }