Tutorial by Examples

Java 7 introduced the very useful Files class Java SE 7 import java.nio.file.Files; import java.nio.file.Paths; import java.nio.file.Path; Path path = Paths.get("path/to/file"); try { byte[] data = Files.readAllBytes(path); } catch(IOException e) { e.printStackTrace();...

import java.awt.Image; import javax.imageio.ImageIO; ... try { Image img = ImageIO.read(new File("~/Desktop/cat.png")); } catch (IOException e) { e.printStackTrace(); }

Java SE 7 byte[] bytes = { 0x48, 0x65, 0x6c, 0x6c, 0x6f }; try(FileOutputStream stream = new FileOutputStream("Hello world.txt")) { stream.write(bytes); } catch (IOException ioe) { // Handle I/O Exception ioe.printStackTrace(); } Java SE 7 byte[] bytes = { 0x48, ...

Streams provide the most direct access to the binary content, so any InputStream / OutputStream implementations always operate on ints and bytes. // Read a single byte from the stream int b = inputStream.read(); if (b >= 0) { // A negative value represents the end of the stream, normal values ...

File f = new File(path); String content = new Scanner(f).useDelimiter("\\Z").next(); \Z is the EOF (End of File) Symbol. When set as delimiter the Scanner will read the fill until the EOF Flag is reached.

Reading a file line by line public class Main { public static void main(String[] args) { try { Scanner scanner = new Scanner(new File("example.txt")); while(scanner.hasNextLine()) { String line = scanner.nextLine(); ...

public void iterateAndFilter() throws IOException { Path dir = Paths.get("C:/foo/bar"); PathMatcher imageFileMatcher = FileSystems.getDefault().getPathMatcher( "regex:.*(?i:jpg|jpeg|png|gif|bmp|jpe|jfif)"); try (Direc...

These examples assume that you already know what Java 7's NIO is in general, and you are used to writing code using java.io.File. Use these examples as a means to quickly find more NIO-centric documentation for migrating. There is much more to Java 7's NIO such as memory-mapped files or opening a Z...

Write to a file test.txt: String filepath ="C:\\test.txt"; FileOutputStream fos = null; try { fos = new FileOutputStream(filepath); byte[] buffer = "This will be written in test.txt".getBytes(); fos.write(buffer, 0, buffer.length); fos.close(); } c...

You can read an a binary file using this piece of code in all recent versions of Java: Java SE 1.4 File file = new File("path_to_the_file"); byte[] data = new byte[(int) file.length()]; DataInputStream stream = new DataInputStream(new FileInputStream(file)); stream.readFully(data); s...

A file can be locked using the FileChannel API that can be acquired from Input Output streams and readers Example with streams // Open a file stream FileInputStream ios = new FileInputStream(filename); // get underlying channel FileChannel channel = ios.getChannel(); /* * t...

We can directly copy data from a source to a data sink using a loop. In this example, we are reading data from an InputStream and at the same time, writing to an OutputStream. Once we are done reading and writing, we have to close the resource. public void copy(InputStream source, OutputStream dest...

Channel uses a Buffer to read/write data. A buffer is a fixed sized container where we can write a block of data at once. Channel is a quite faster than stream-based I/O. To read data from a file using Channel we need to have the following steps- We need an instance of FileInputStream. FileInput...

We can use Channel to copy file content faster. To do so, we can use transferTo() method of FileChannel . import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.nio.channels.FileChannel; public class FileCopier { ...

Reading file using a BufferedInputStream generally faster than FileInputStream because it maintains an internal buffer to store bytes read from the underlying input stream. import java.io.BufferedInputStream; import java.io.FileInputStream; import java.io.IOException; public class FileReadin...

To write data to a file using Channel we need to have the following steps: First, we need to get an object of FileOutputStream Acquire FileChannel calling the getChannel() method from the FileOutputStream Create a ByteBuffer and then fill it with data Then we have to call the flip() method of ...

We can use PrintStream class to write a file. It has several methods that let you print any data type values. println() method appends a new line. Once we are done printing, we have to flush the PrintStream. import java.io.FileNotFoundException; import java.io.PrintStream; import java.time.Local...

public void iterate(final String dirPath) throws IOException { final DirectoryStream<Path> paths = Files.newDirectoryStream(Paths.get(dirPath)); for (final Path path : paths) { if (Files.isDirectory(path)) { System.out.println(path.getFileName()); } } ...

To make a new directory from a File instance you would need to use one of two methods: mkdirs() or mkdir(). mkdir() - Creates the directory named by this abstract pathname. (source) mkdirs() - Creates the directory named by this abstract pathname, including any necessary but nonexistent parent d...

Sometimes a poorly designed 3rd-party library will write unwanted diagnostics to System.out or System.err streams. The recommended solutions to this would be to either find a better library or (in the case of open source) fix the problem and contribute a patch to the developers. If the above solu...