How to Check if a File Exists in Kotlin
In Kotlin, we can use the `File` built-in `exists()` method to check if a file exists.
Java – How to save a String to a File
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) […]
Copy file to / from server via SCP command
SCP uses Secure Shell (SSH) to transfer data between client and remote server, it’s fast and secure. In this article, we will show you two common SCP copying examples : Copying data from your computer to remote server. Copying data from remote server to your computer. 1. Copying data to Remote Server Example 1.1 – […]
How to read file in Java – FileInputStream
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 […]
How to make a file read only in Java
A Java program to demonstrate the use of java.io.File setReadOnly() method to make a file read only. Since JDK 1.6, a new setWritable() method is provided to make a file to be writable again. Example package com.mkyong; import java.io.File; import java.io.IOException; public class FileReadAttribute { public static void main(String[] args) throws IOException { File file […]
How to check if a file is hidden in Java
A Java program to demonstrate the use of java.io.File isHidden() to check if a file is hidden. package com.mkyong; import java.io.File; import java.io.IOException; public class FileHidden { public static void main(String[] args) throws IOException { File file = new File("c:/hidden-file.txt"); if(file.isHidden()){ System.out.println("This file is hidden"); }else{ System.out.println("This file is not hidden"); } } } Note […]
Java – Convert File to Hex
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 | […]
How to set the file permission in Java
In Java, file permissions are very OS specific: *nix , NTFS (windows) and FAT/FAT32, all have different kind of file permissions. Java comes with some generic file permission to deal with it. Check if the file permission allow : file.canExecute(); – return true, file is executable; false is not. file.canWrite(); – return true, file is […]
How to create a file in Java
In Java, there are many ways to create and write to a file. Files.newBufferedWriter (Java 8) Files.write (Java 7) PrintWriter File.createNewFile Note I prefer the Java 7 nio Files.write to create and write to a file, because it has much cleaner code and auto close the opened resources. Files.write( Paths.get(fileName), data.getBytes(StandardCharsets.UTF_8)); 1. Java 8 Files.newBufferedWriter […]
Java – How to save byte[] to a file
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 […]
Java – How to convert File to byte[]
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 […]
How to assign file content into a variable in Java
Most people will read the file content and assign to StringBuffer or String line by line. Here’s another trick that may interest you – how to assign whole file content into a variable with one Java’s statement, try it 🙂 Example In this example, you will use DataInputStreamto convert all the content into bytes, and […]
How to delete files with certain extension only
In Java, you can implements the FilenameFilter, override the accept(File dir, String name) method, to perform the file filtering function. In this example, we show you how to use FilenameFilter to list out all files that are end with “.txt” extension in folder “c:\\folder“, and then delete it. package com.mkyong.io; import java.io.*; public class FileChecker […]
Java – Create file checksum with SHA and MD5
In this article, we will show you how to use a SHA-256 and MD5 algorithm to generate a checksum for a file. MessageDigest.getInstance(“algorithm”) Apache Commons Codec 1. MessageDigest d:\server.log hello world 1.1 Generate a file checksum with a SHA256 algorithm. FileCheckSumSHA.java package com.mkyong.hashing; import java.io.FileInputStream; import java.io.IOException; import java.security.DigestInputStream; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class […]
How to read file in Java – BufferedInputStream
Here is another example to show how to read a file in Java with BufferedInputStream and DataInputStream classes. The readLine() from the type DataInputStream is deprecated. Sun officially announced this method can not convert property from bytes to characters. It’s advised to use BufferedReader. You may interest to read this How to read file from […]