This article shows how to convert a file into a hexadecimal (hex) representative format. The idea is to read the file into an InputStream and uses String.format(%X) to convert each byte into a hex code.
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. FileOutputStream is the best alternative. If we have Apache Commons IO, try FileUtils.
In Java, we can use Files.readAllBytes(path) to convert a File object into a byte. Before Java 7, we can initiate a new byte with a predefined size (same with the file length), and use FileInputStream to read the file data into the new byte. We also can use FileUtils from Apache Commons IO to read the file.
In this article, we will show you how to use a SHA-256 and MD5 algorithm to generate a checksum for a file. We have 2 ways: (1) using MessageDigest.getInstance(“algorithm”), (2) using Apache Commons Codec
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 🙂. In this example, you will use DataInputStreamto convert all the content into bytes, and create a String variable with the converted bytes.
A Java program to demonstrate the use of java.io.File isHidden() to check if a file is hidden. The isHidden() method is system dependent, on UNIX platform, a file is considered hidden if it’s name is begins with a “dot” symbol (‘.’); On Microsoft Windows platform, a file is considered to be hidden, if it’s marked as hidden in the file properties.
In Java, we use FileInputStream to read bytes from a file, such as an image file or binary file. The FileInputStream.read() reads a byte at a time, and it will return a -1 if it reached the end of the file. The FileInputStream.available() to check the remaining bytes that can be read. The FileInputStream.read(byte b) to read predefined bytes into a byte array; it will significantly increase the read performance. The common practice uses BufferedInputStream to wrap the FileInputStream to provide a buffer cache to increase the read performance. It’s also common to use InputStreamReader to convert FileInputStream to BufferedReader, and read it line by line.
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.
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: Executable, Readable, Writable. In *nix system, you may need to configure more specifies about file permission, e.g set a 777 permission for a file or directory, however, Java IO classes do not have ready method for it, but you can use the following dirty workaround : Runtime.getRuntime().exec(“chmod 777 file”);
In Java, there are many ways to create and write to a file: using Files.newBufferedWriter (Java 8), using Files.write (Java 7), using PrintWriter, using File.createNewFile