In Java, we can use the Files.walk() API to traverse all files from a folder and its subfolders. Table of contents: 1. Traverse all files from a folder in Java 2. Traverse all files from a folder and its subfolders in Java 3. List all file name from a folder in Java 4. Find a […]
The Files.find API is available since Java 8. It searches or finds files from a file tree quickly. Topics Files.find() method signature Find files by filename Find files by file size Find files by last modified time In the old days, we always use an error-prone recursive loop to walk a file tree. This Java […]
This article shows how to convert a File to a Path in Java. java.io.File => java.nio.file.Path // Convert File to Path File file = new File("/home/mkyong/test/file.txt"); Path path = file.toPath(); java.nio.file.Path => java.io.File // Convert Path to File Path path = Paths.get("/home/mkyong/test/file.txt"); File file = path.toFile(); 1. Convert File to Path In Java, we can […]
In Java, we can use Files.size to get the size of a file; for the directory or folder size, we need to count the size of a directory recursively (sum of the Files.size of all files). This example shows a few common ways to get the size of a directory or folder. FileVisitor (Java 7) […]
In Java, we can use DateTimeFormatter to convert the FileTime to other custom date formats. public static String formatDateTime(FileTime fileTime) { LocalDateTime localDateTime = fileTime .toInstant() .atZone(ZoneId.systemDefault()) .toLocalDateTime(); return localDateTime.format( DateTimeFormatter.ofPattern("MM/dd/yyyy HH:mm:ss")); } 1. File Last Modified Time This example displays the last modified time of a file in a custom date format. GetLastModifiedTime.java package […]
In Java, we can use the NIO createFile() to assign file permission during file creation. Files.java package java.nio.file; public static Path createFile(Path path, FileAttribute<?>… attrs) throws IOException But, the createFile() fails to assign the group writes file permission to a file on the Unix system? Path path = Paths.get("/home/mkyong/test/runme.sh"); Set<PosixFilePermission> perms = PosixFilePermissions.fromString("rwxrwxrwx"); Files.createFile(path, PosixFilePermissions.asFileAttribute(perms)); […]
For file path or directory separator, the Unix system introduced the slash character / as directory separator, and the Microsoft Windows introduced backslash character \ as the directory separator. In a nutshell, this is / on UNIX and \ on Windows. In Java, we can use the following three methods to get the platform-independent file […]
This article will show you a few ways to declare and use a multi-line string in Java. String + String + String StringBuilder String.format StringWriter String.join (Java 8) Files.lines (Java 8) (""") Java 13 and Java 14 text blocks (preview feature) Review an HTML and a JSON string, and we will use the above methods […]
In Java, we have many ways to convert a File to a String. A text file for testing later. c:\\projects\\app.log A B C D E 1. Java 11 – Files.readString A new method Files.readString is added in java.nio.file.Files, it makes reading a string from File much easier. FileToString1.java package com.mkyong; import java.io.IOException; import java.nio.file.Files; import […]
In Java, there are many ways to write a String to a File. 1. Java 11 – Files.writeString Finally, a new method added in java.nio to save a String into a File easily. StringToFileJava11.java package com.mkyong; import java.io.IOException; import java.nio.charset.StandardCharsets; import java.nio.file.Files; import java.nio.file.Paths; import java.nio.file.StandardOpenOption; public class StringToFileJava11 { public static void main(String[] args) […]
In Java, we can use Files.write to create and write to a file. String content = "…"; Path path = Paths.get("/home/mkyong/test.txt"); // string -> bytes Files.write(path, content.getBytes(StandardCharsets.UTF_8)); The Files.write also accepts an Iterable interface; it means this API can write a List to a file. List<String> list = Arrays.asList("a", "b", "c"); Files.write(path, list); Short History […]
The Files.walk API is available since Java 8; it helps to walk a file tree at a given starting path. Topics Files.walk() method signature List all files List all folders or directories Find files by file extension Find files by filename Find files by file size Update all files last modified date 1. Files.walk() method […]
This article covers 3 ways to read a text file line by line : Java NIO libraries – FileChannel to read the files. It is a non-blocking mode of reading files BufferedReader – Which is a blocking operation i.e it blocks any other read/write request to the file until it has completed the task. Apache […]
In Java, we can use getResourceAsStream or getResource to read a file or multiple files from a resources folder or root of the classpath. The getResourceAsStream method returns an InputStream. // the stream holding the file content InputStream is = getClass().getClassLoader().getResourceAsStream("file.txt"); // for static access, uses the class name directly InputStream is = JavaClassName.class.getClassLoader().getResourceAsStream("file.txt"); The […]
In Java, we can use the Java 1.7 FileVisitor or Apache Commons IO FileUtils.copyDirectory to copy a directory, which includes its sub-directories and files. This article shows a few of the common ways to copy a directory in Java. FileVisitor (Java 7+) FileUtils.copyDirectory (Apache commons-io) Custom Copy using Java 7 NIO and Java 8 Stream. […]
If we use the NIO Files.delete to delete a non-empty directory in Java, it throws DirectoryNotEmptyException; for legacy IO File.delete to delete a non-empty directory, it returns a false. The standard solution is to loop the directory recursively, and delete all its children’s contents first (sub-files or sub-directories), and delete the parent later. This example […]
In Java, we can use the NIO Files.createDirectory to create a directory or Files.createDirectories to create a directory including all nonexistent parent directories. try { Path path = Paths.get("/home/mkyong/a/b/c/"); //java.nio.file.Files; Files.createDirectories(path); System.out.println("Directory is created!"); } catch (IOException e) { System.err.println("Failed to create directory!" + e.getMessage()); } 1. Create Directory – Java NIO 1.1 We can […]
In Java, we can use the following two Files.createTempFile() methods to create a temporary file in the default temporary-file directory. Path createTempFile(Path dir, String prefix, String suffix, FileAttribute<?>… attrs) throws IOException Path createTempFile(String prefix, String suffix, FileAttribute<?>… attrs) throws IOException The default temporary file folder is vary on operating system. Windows – %USER%\AppData\Local\Temp Linux – […]
In Java, we can use the NIO Files.setLastModifiedTime(path, FileTime) to update the last modified date or time of a file. Path path = Paths.get("/path/file"); LocalDate newLocalDate = LocalDate.of(1997, 12, 31); // year, month, dayOfMonth, hour, minute, second LocalDateTime newLocalDateTime = LocalDateTime.of(1999, 9, 30, 10, 30, 22); // convert LocalDateTime to Instant Instant instant = newLocalDateTime.toInstant(ZoneOffset.UTC); […]
This article shows how to use the following Java APIs to append text to the end of a file. Files.write – Append a single line to a file, Java 7. Files.write – Append multiple lines to a file, Java 7, Java 8. Files.writeString – Java 11. FileWriter FileOutputStream FileUtils – Apache Commons IO. In Java, […]
In Java (@since 1.7), we can use the NIO Files.readAttributes to get all the file metadata, including the file creation date. Path file = Paths.get(fileName); BasicFileAttributes attr = Files.readAttributes(file, BasicFileAttributes.class); System.out.println("creationTime: " + attr.creationTime()); // creationTime: 2020-07-20T09:29:54.627222Z 1. Files.readAttributes (NIO) This example uses Files.readAttributes to print the file creation date. GetCreationDate1.java package com.mkyong.io.howto; import java.io.IOException; […]
This article shows four ways to copy a file in Java. Files.copy (NIO) Apache Commons IO Guava Plain Java In Java 7+, the NIO Files.copy is the simplest way to copy a file, because it is a built-in API. Before Java 7, the Apache Commons IO FileUtils.copyFile is a preferable solution because the legacy IO […]
In Java, we can use the NIO Files.delete() or Files.deleteIfExists() to delete a temporary file, it works the same like delete a regular text file. // create a temporary file Path path = Files.createTempFile(null, ".log"); // delete Files.delete(path); // or if(Files.deleteIfExists(path)){ // success }else{ // file does not exist } 1. Delete Temporary File – […]
In Java, we can use the NIO Files.delete(Path) and Files.deleteIfExists(Path) to delete a file. 1. Delete a file with Java NIO 1.1 The Files.delete(Path) deletes a file, returns nothing, or throws an exception if it fails. DeleteFile1.java package com.mkyong.io.file; import java.io.IOException; import java.nio.file.Files; import java.nio.file.Paths; public class DeleteFile1 { public static void main(String[] args) { […]
In Java, we can use the NIO Files.move(source, target) to rename or move a file. import java.io.IOException; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; //… Path source = Paths.get("/home/mkyong/newfolder/test1.txt"); Path target = Paths.get("/home/mkyong/newfolder/test2.txt"); try{ Files.move(source, target); } catch (IOException e) { e.printStackTrace(); } 1. Rename a file in the same directory. 1.1 This example renames a […]
The temporary file is just a regular file created on a predefined directory. In Java, we can use the NIO Files.write() to write data to a temporary file. // create a temporary file Path tempFile = Files.createTempFile(null, null); // Writes a string to the above temporary file Files.write(tempFile, "Hello World\n".getBytes(StandardCharsets.UTF_8)); // Append List<String> content = […]
In Java, for NIO Path, we can use path.toAbsolutePath() to get the file path; For legacy IO File, we can use file.getAbsolutePath() to get the file path. For symbolic links or file path contains . or .., we can use path.toRealPath() or file.getCanonicalPath() to get the real file pah. Below is the mapping of File […]
This article shows few Java examples to get the total number of lines in a file. The steps are similar: Open the file. Read line by line, and increases count + 1 each line. Close the file. Read the count. Test Java Methods: Files.lines BufferedReader LineNumberReader BufferedInputStream At the end of the article, we also […]
In Java, we can use Files.size(path) to get the size of a file in bytes. // size in bytes long bytes = Files.size(path); 1. Files.size (NIO) This example uses NIO Files.size(path) to print the size of an image file (140 kb). GetFileSize.java package com.mkyong.io.howto; import java.io.IOException; import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; public class GetFileSize […]
In Java, we can use System.getProperty("java.io.tmpdir") to get the default temporary file location. For Windows, the default temporary folder is %USER%\AppData\Local\Temp For Linux, the default temporary folder is /tmp 1. java.io.tmpdir Run the below Java program on a Ubuntu Linux. TempFilePath1 package com.mkyong.io.temp; public class TempFilePath1 { public static void main(String[] args) { String tmpdir […]
This article shows a few ways to save a byte[] into a file. For JDK 1.7 and above, the NIO Files.write is the simplest solution to save byte[] to a file. // bytes = byte[] Path path = Paths.get("/path/file"); Files.write(path, bytes); FileOutputStream is the best alternative. try (FileOutputStream fos = new FileOutputStream("/path/file")) { fos.write(bytes); //fos.close […]
In Java, we can use Files.readAllBytes(path) to convert a File object into a byte[]. import java.nio.file.Files; import java.nio.file.Path; import java.nio.file.Paths; String filePath = "/path/to/file"; // file to byte[], Path byte[] bytes = Files.readAllBytes(Paths.get(filePath)); // file to byte[], File -> Path File file = new File(filePath); byte[] bytes = Files.readAllBytes(file.toPath()); P.S The NIO Files class is […]
In this tutorial, we will learn how to unzip a ZIP file using Java’s built-in java.util.zip package, while also discussing the Zip Slip vulnerability and how to avoid it. Table of Contents: 1. Extracting a ZIP File in Java 2. Understanding the Zip Slip Vulnerability What is Zip Slip? How to Prevent Zip Slip? Secure […]
Learn how to easily zip files and directories in Java using `java.util.zip`, `Files.copy`, and the Zip File System Provider.
This article shows how to Java 8 Files.walk to walk a file tree and stream operation filter to find files that match a specific file extension from a folder and its subfolders. // find files matched `png` file extension from folder C:\\test try (Stream<Path> walk = Files.walk(Paths.get("C:\\test"))) { result = walk .filter(p -> !Files.isDirectory(p)) // […]
In Java, we can use Files.readAttributes() to get the file metadata or attribute, and then lastModifiedTime() to display the last modified date of a file. Path file = Paths.get("/home/mkyong/file.txt"); BasicFileAttributes attr = Files.readAttributes(file, BasicFileAttributes.class); System.out.println("lastModifiedTime: " + attr.lastModifiedTime()); 1. BasicFileAttributes (NIO) This example uses the java.nio.* to display the file attributes or metadata – creation […]
In Java, we can use System.getProperty("user.dir") to get the current working directory, the directory from where your program was launched. String dir = System.getProperty("user.dir"); // directory from where the program was launched // e.g /home/mkyong/projects/core-java/java-io System.out.println(dir); One of the good things about this system property user.dir is we can easily override the system property via […]
In Java, we can use Files.exists(path) to test whether a file exists. The path can be a file or a directory. It is better to combine with !Files.isDirectory(path) to ensure the existing file is not a directory. Path path = Paths.get("/home/mkyong/test/test.log"); // file exists and it is not a directory if(Files.exists(path) && !Files.isDirectory(path)) { System.out.println("File […]
Below are some Java examples of converting InputStream to a File. Plain Java – FileOutputStream Apache Commons IO – FileUtils.copyInputStreamToFile Java 7 – Files.copy Java 9 – InputStream.transferTo 1. Plain Java – FileOutputStream This example downloads the google.com HTML page and returns it as an InputStream. And we use FileOutputStream to copy the InputStream into […]
In Java, the InputStreamReader accepts a charset to decode the byte streams into character streams. We can pass a StandardCharsets.UTF_8 into the InputStreamReader constructor to read data from a UTF-8 file. import java.nio.charset.StandardCharsets; //… try (FileInputStream fis = new FileInputStream(file); InputStreamReader isr = new InputStreamReader(fis, StandardCharsets.UTF_8); BufferedReader reader = new BufferedReader(isr) ) { String str; […]
