从文件中读取 N 行并保存到新文件中

Question

例如，如何从readFile或n行中读取20行并将其保存到另一个文件(writeFile)？

public class Test_read_file {
  public static List<String> readFile() throws IOException {
    try(BufferedReader br = new BufferedReader(new FileReader("C:\\\\Users\\\\Admin\\\\Desktop\\\\Work Files\\\\314-WO0000001133814\\\\Cards\\\\MBD10760_182.out"))){
        List<String> listOfData = new ArrayList<>();
        String d;
        while((d = br.readLine()) != null){
            listOfData.add(d);
        }
        return listOfData;
    }
}

public static void writeFile(List<String> listOfData) throws IOException{
    try(BufferedWriter bw = new BufferedWriter(new FileWriter("C:\\\\Users\\\\Admin\\\\Desktop\\\\Work Files\\\\314-WO0000001133814\\\\Cards\\\\MBD10760_187.out"))){
        for(String str: listOfData){
            bw.write(str);
            bw.newLine();
        }
    }
}

public static void main(String[] args) throws IOException {
    List<String> data = readFile();
    writeFile(data);
}
}

Answer 1

只需在检查 listOfData 大小时添加到：

 while( ((d = br.readLine()) != null) && listOfData.size()<20 ) {
            listOfData.add(d);
}

Answer 2

假设您的代码工作正常：

public static List<String> readFile(int n) throws IOException {
    try(BufferedReader br = new BufferedReader(new 
FileReader("C:\\\\Users\\\\Admin\\\\Desktop\\\\Work Files\\\\314- 
WO0000001133814\\\\Cards\\\\MBD10760_182.out"))){
        List<String> listOfData = new ArrayList<>();
        String d;
        while((d = br.readLine()) != null && n>0){
            listOfData.add(d);
            n--;
        }
        return listOfData;
    }

只需告诉循环它应该读取多少行。如果文件少于 n 行，则 while 循环的第一条语句将为 return null 并且它将中断循环。否则，当它读取 n 行时，由于 while 循环中的第二条语句，它将再次中断循环。

Answer 3

 public static void main(String[] args) throws IOException {
     Path pathFrom = Paths.get("C:\Users\Admin\Desktop\Work Files\314-WO0000001133814\Cards\MBD10760_182.out\"");
     Path pathTo = Paths.get("C:\Users\Admin\Desktop\Work Files\314-WO0000001133814\Cards\MBD10760_187.out\"");
     Files.write(pathTo, Files.lines(pathFrom).limit(20).collect(Collectors.toList()));
 }

从文件中读取 N 行并保存到新文件中

Read N lines from file and save it to new file

java

file-io

file

text-files