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 …
This article shows how to convert an object to byte[] or byte array and vice versa in Java. 1. Convert an object to byte[] The below example show how to use ByteArrayOutputStream and ObjectOutputStream to convert an object to byte[]. // Convert object to byte[] public static byte[] convertObjectToBytes(Object obj) { ByteArrayOutputStream boas = new …
This article shows you how to add, check and remove the byte order mark (BOM) from a UTF-8 file. The UTF-8 representation of the BOM is the byte sequence 0xEF, 0xBB, 0xBF (hexadecimal), at the beginning of the file. 1. Add BOM to a UTF-8 file 2. Check if a file contains UTF-8 BOM 3. …
Note The BufferedReader reads characters; while the InputStream is a stream of bytes. The BufferedReader can’t read the InputStream directly; So, we need to use an adapter like InputStreamReader to convert bytes to characters format. For example: // BufferedReader -> InputStreamReader -> InputStream BufferedReader br = new BufferedReader( new InputStreamReader(inputStream, StandardCharsets.UTF_8)); 1. Reads a file …
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 get the file extension of a file in Java. Topics Get file extension normal Get file extension strict Get file extension hardcode Apache Common IO – FilenameUtils Path: /path/foo.txt -> File Extension: txt Path: . -> File Extension: Path: .. -> File Extension: Path: /path/run.exe -> File Extension: exe Path: …
In Java, we can use the following code snippets to get the path of a running JAR file. // static String jarPath = ClassName.class .getProtectionDomain() .getCodeSource() .getLocation() .toURI() .getPath(); // non-static String jarPath = getClass() .getProtectionDomain() .getCodeSource() .getLocation() .toURI() .getPath(); Sample output. Terminal /home/mkyong/projects/core-java/java-io/target/java-io.jar 1. Get the path of running JAR 1.1 Create an executable …
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 …
This article shows how to use JSch library to run or execute a shell script in a remote server via SSH. pom.xml <dependency> <groupId>com.jcraft</groupId> <artifactId>jsch</artifactId> <version>0.1.55</version> </dependency> 1. Run Remote Shell Script This Java example uses JSch to SSH login a remote server (using password), and runs a shell script hello.sh. 1.1 Here is a …
This article shows how to do file transfer from a remote server to the local system and vice versa, using SSH File Transfer Protocol (SFTP) in Java. P.S Tested with JSch 0.1.55 1. JSch Dependency pom.xml <dependency> <groupId>com.jcraft</groupId> <artifactId>jsch</artifactId> <version>0.1.55</version> </dependency> 2. File Transfer – JSch Examples 2.1 In JSch, we can use put and …
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 …
The newline character, also called end of line (EOL), line break, line feed, line separator or carriage return, is a control character to tell the end of a line of text, and the next character should start at a new line. On the Windows system, it is \r\n, on the Linux system, it is \n. …
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, Serialization means converting Java objects into a byte stream; Deserialization means converting the serialized object’s byte stream back to the original Java object. Table of contents. 1. Hello World Java Serialization 2. java.io.NotSerializableException 3. What is serialVersionUID? 4. What is transient? 5. Serialize Object to File 6. Why need Serialization in Java? 7. …
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) …
This article focus on a few of the commonly used methods to read a file in Java. Files.lines, return a Stream (Java 8) Files.readString, returns a String (Java 11), max file size 2G. Files.readAllBytes, returns a byte[] (Java 7), max file size 2G. Files.readAllLines, returns a List<String> (Java 8) BufferedReader, a classic old friend (Java …
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 shows you how to download a file from an URL by using the following methods : Apache Commons IO Java NIO 1. Apache Commons IO 1.1 This is still my prefer way to download a file from the Internet, simple and clean. Read the signature : org.apache.commons.io.FileUtils //int = number of milliseconds public …
This article talks about reading and writing PDF using iText PDF library. pom.xml <dependency> <groupId>com.itextpdf</groupId> <artifactId>itextpdf</artifactId> <version>5.5.10</version> </dependency> P.S Tested with iTextPdf 5.5.10 1. iText – Write PDF iText PdfWriter example to write content to a PDF file. PdfWriteExample.java package com.mkyong; import com.itextpdf.text.*; import com.itextpdf.text.pdf.PdfWriter; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; public class …
Java object Serialization is an API provided by Java Library stack as a means to serialize Java objects. Serialization is a process to convert objects into a writable byte stream. Once converted into a byte-stream, these objects can be written to a file. The reverse process of this is called de-serialization. A Java object is …
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 …
This article shows how to read and parse a comma-separated values (CSV) file. Topics: CSV file and RFC 4180 OpenCSV – Read and Parse CSV file OpenCSV – Convert CSV file to Object Parse CSV file Challenges – Embedded commas, double quotes, and line breaks Single class to read and parse a CSV file String#split …
Here’s an example to show you how to search a file named “post.php” from directory “/Users/mkyong/websites” and all its subdirectories recursively. FileSearch.java package com.mkyong; import java.io.File; import java.util.ArrayList; import java.util.List; public class FileSearch { private String fileNameToSearch; private List<String> result = new ArrayList<String>(); public String getFileNameToSearch() { return fileNameToSearch; } public void setFileNameToSearch(String fileNameToSearch) { …
Recently, testing on PrimeFaces’ idleMonitor component. <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://java.sun.com/jsf/html" xmlns:f="http://java.sun.com/jsf/core" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:p="http://primefaces.org/ui"> <h:head> </h:head> <h:body> <h1>PrimeFaces and idleMonitor</h1> <p:growl id="messages" showDetail="true" sticky="true" /> <p:idleMonitor timeout="10000" update="messages"> <p:ajax event="idle" listener="#{idleBean.idleListener}" update="messages" /> </p:idleMonitor> </h:body> </html> Problem After 10 seconds, console prompts java.io.IOException: Not in GZIP format? That’s weird, what GZIP to do iwith idleMonitor …
This article shows how to convert an PNG image format to an JPEG image format in Java. 1. PNG Image Below is a PNG image with a transparent background. 2. Java Convert PNG to JPEG Since the JPEG image format doesn’t support the transparent background, we will create a white background as a replacement. Below …
In Java, we use FileInputStream to read bytes from a file, such as an image file or binary file. Topics FileInputStream – Read a file FileInputStream – Remaining bytes FileInputStream – Better performance FileInputStream vs BufferedInputStream InputStreamReader – Convert FileInputStream to Reader FileInputStream – Read a Unicode file Note However, all the below examples use …
This article shows a few ways to convert an java.io.InputStream to a String. Table of contents 1. ByteArrayOutputStream 2. InputStream#readAllBytes (Java 9) 3. InputStreamReader + StringBuilder 4. InputStreamReader + BufferedReader (modified line breaks) 5. Java 8 BufferedReader#lines (modified line breaks) 6. Apache Commons IO 7. Download Source Code 8. References What are modified line breaks? …
In Java, we can use ByteArrayInputStream to convert a String to an InputStream. String str = "mkyong.com"; InputStream is = new ByteArrayInputStream(str.getBytes(StandardCharsets.UTF_8)); Table of contents 1. ByteArrayInputStream 2. Apache Commons IO – IOUtils 3. Download Source Code 4. References 1. ByteArrayInputStream This example uses ByteArrayInputStream to convert a String to an InputStream and saves it …
This article shows how to convert a file into a hexadecimal (hex) representative format. for example, below is a text file. /path/to/text.txt ABCDEFG 12345678 !@#$%^&*() Testing only And we will convert the above file into the following hex format. 41 42 43 44 45 46 47 0D 0A 31 32 33 34 35 36 | …
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 …
This article shows how to move a file to another directory in the same file drive or remote server. Files.move – Move file in local system. JSch – Move file to remove server (SFTP) 1. Move file to another directory This Java example uses NIO Files.move to move a file from to another directory in …
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 – …