FileUtil + FileUtils common writing reference

File permissions
Reference: https://www.breakyizhan.com/java/5013.html
Files and folders are the same thing here.

	public static boolean setExecutable(String path) {
    
    
        File file = FileUtils.getFile(path);
        file.setReadable(true, false);
        return file.setExecutable(true, false);
    }

Create a file:

file.createNewFile()

Create a folder:

dir.mkdirs()

Deletion of files and folders:

file.delete()

When creating a new file, it is safe to use FileUtils.getFile(String path) instead of directly new

File information:
Get the latest modification time:

file.lastModified()

The return value is long, which is the number of milliseconds, as a reference: the number of milliseconds at the present moment is: System.currentTimeMillis(); the
format of the two is the same

Write file: keep adding to the end of the file in the form of append

	try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file, true)))) {
    
    
            writer.write(str);
        } catch (IOException e) {
    
    
            logger.error("Failed to close resource", e);
        }

Way of flushing

		try (FileWriter writer = new FileWriter(file)) {
    
    
            writer.write("");
            writer.flush();
        } catch (IOException e) {
    
    
            logger.error("IOException in writing file ", e);
        }

The contents of multiple files (fpath) are unified into one file (resultFile), and the higher-performance FileChannel is used

		File resultFile = FileUtils.getFile(resultPath);
		//向resultFileChannel写入字节流
        try (FileChannel resultFileChannel = new FileOutputStream(resultFile, true).getChannel()) {
    
    
            for (int i = 0; i < fpaths.length; i++) {
    
    
//建立blk，从blk中读取字节流写入resultFileChannel
                try (FileChannel blk = new FileInputStream(files[i]).getChannel()) {
    
    
// 在result的末尾插入blk大小的字节流
                    resultFileChannel.transferFrom(blk, resultFileChannel.size(), blk.size());
                } catch (IOException e) {
    
    
                    logger.error("IOException occurs", e);
                }
            }
        }

Query FileChannel: https://blog.csdn.net/developlee/article/details/90543160
Reference: https://blog.csdn.net/akon_vm/article/details/7429245
FileChannel is better than RandomAccessFile in read and write performance, yes So-called memory mapped files

Read the file:

	StringBuffer sb = new StringBuffer();
    try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
    
    
        String str = null;
        str = reader.readLine();
        if (str != null) {
    
    
            sb.append(str);
        }
        str = reader.readLine();
        while (str != null) {
    
    
            sb.append(System.lineSeparator()).append(str);
            str = reader.readLine();
        }
    } catch (IOException e) {
    
    
        logger.error("IOException occurs!", e);
        sb.setLength(0);
    }
    return sb.toString();

Use RandomAccessFile to read a fixed value from back to front, such as 10 here:

	long pos = 0L;
    try (RandomAccessFile raf = new RandomAccessFile(file, "r")) {
    
    
        long len = raf.length();
        if (len == 0) {
    
    
            return 0;
        } else {
    
    
            pos = len - 1;
            while (pos-- > 0) {
    
    
                raf.seek(pos);
                if (raf.read() == 10) {
    
    
                    break;
                }
            }
            return pos + 1;
        }
    }