How do I get the absolute path of a file in Java?

By Wayan in Core API, IO 2 Comments

The following code snippet shows you how to get the absolute path of a file. To do this we use the java.io.File object getAbsolutePath() method.

package org.kodejava.io;

import java.io.File;

public class AbsolutePathExample {
    public static void main(String[] args) {
        // Create an instance of File called file.
        File file = new File("README.md");

        // Now we want to know where is exactly this file is located in our file 
        // system. To do this we can use the getAbsolutePath() method of the File
        // class.
        String absolutePath = file.getAbsolutePath();

        // Print out the JavaProgrammingBook.pdf location to the console.
        System.out.println("AbsolutePath = " + absolutePath);
    }
}

Here is the result of the program:

AbsolutePath = F:\Wayan\Kodejava\kodejava-example\README.md

How do I get file size in Java?

By Wayan in Core API, IO 0 Comment

This example will show you how to get the size of a file. To obtain the size of a file you can use the File‘s length() method. The length() method return the file size in bytes.

package org.kodejava.io;

import java.io.File;

public class FileSize {
    public static void main(String[] args) {
        File file = new File("README.md");

        // Get the size of a file in bytes.
        long fileSize = file.length();

        // Using Java printf() method to print the file size
        System.out.printf("File size: %,d bytes.%n", fileSize);
    }
}

This will print something like:

File size: 51,981 bytes.

If you want to format the file size in Kilobytes, Megabytes or Gigabytes check the following example How do I create a human-readable file size?.

How do I get file’s last modification date?

By Wayan in Core API, IO 0 Comment

To get file last modification date we can use the lastModified() method of the File class. This method returns a long value. After getting this value you can create an instance of java.util.Date class and pass this value as the parameter. This Date will hold the file’s last modification date.

package org.kodejava.io;

import java.io.File;
import java.util.Date;

public class FileLastModificationDate {
    public static void main(String[] args) {
        // Create an instance of file object.
        File file = new File("README.md");
        if (file.exists()) {
            // Get the last modification information.
            long lastModified = file.lastModified();

            // Create a new date object and pass last modified
            // information to the date object.
            Date date = new Date(lastModified);

            // We know when the last time the file was modified.
            System.out.println(date);
        }
    }
}

How do I delete a file in Java?

By Wayan in Core API, IO 0 Comment

In this example you will see how to delete a file in Java. To delete a file we start by creating a File object that represent the file to be deleted. We use the exists() method to check if the file is exists before we try to delete it.

To delete the file we call the delete() method of the File object. If the file was successfully deleted the method will return a boolean true result, otherwise it will return false. Let’s try the code snippet below.

package org.kodejava.io;

import java.io.File;

public class FileDeleteExample {
    public static void main(String[] args) {
        // When want to delete a file named readme.txt
        File file = new File("write.txt");

        // Checks if the file is exists before deletion.
        if (file.exists()) {
            System.out.println("Deleting " + file.getAbsolutePath());
            // Use the delete method to delete the given file.
            boolean deleted = file.delete();
            if (deleted) {
                System.out.println(file.getAbsolutePath() + " was deleted.");
            }
        } else {
            System.out.println(file.getAbsolutePath() + " not found.");
        }
    }
}

How do I use Java NIO to copy file?

By Wayan in Core API, IO 0 Comment

The following code snippet show you how to copy a file using the NIO API. The NIO (New IO) API is in the java.nio.* package. It requires at least Java 1.4 because the API was first included in this version. The JAVA NIO is a block based IO processing, instead of a stream based IO which is the old version IO processing in Java.

package org.kodejava.io;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.channels.FileChannel;
import java.nio.ByteBuffer;

public class CopyFileExample {
    public static void main(String[] args) throws Exception {
        String source = "medical-report.txt";
        String destination = "medical-report-final.txt";

        FileInputStream fis = new FileInputStream(source);
        FileOutputStream fos = new FileOutputStream(destination);

        FileChannel inputChannel = fis.getChannel();
        FileChannel outputChannel = fos.getChannel();

        // Create a buffer with 1024 size for buffering data
        // while copying from source file to destination file.
        // To create the buffer here we used a static method
        // ByteBuffer.allocate()
        ByteBuffer buffer = ByteBuffer.allocate(1024);

        // Here we start to read the source file and write it
        // to the destination file. We repeat this process
        // until the read method of input stream channel return
        // nothing (-1).
        while (true) {
            // Read a block of data and put it in the buffer
            int read = inputChannel.read(buffer);

            // Did we reach the end of the channel? if yes
            // jump out the while-loop
            if (read == -1) {
                break;
            }

            // flip the buffer
            buffer.flip();

            // write to the destination channel and clear the buffer.
            outputChannel.write(buffer);
            buffer.clear();
        }
    }
}