How do I get file basic attributes?

By I Wayan Saryada in Core API, IO 2 Comments

This example you’ll learn how to get file’s basic attributes. Basic file attributes are attributes that are common to many file systems and consist of mandatory and optional file attributes as defined by the BasicFileAttributes interface.

The file’s basic attributes include file’s date time information such as the creation time, last access time, last modified time. You can also check whether the file is a directory, a regular file, a symbolic link or something else. You can also get the size of the file.

Let’s see the code snippet below:

package org.kodejava.io;

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;

public class FileAttributesDemo {
    public static void main(String[] args) throws Exception {
        String path = "D:/resources/data.txt";

        Path file = Paths.get(path);
        BasicFileAttributes attr = Files.readAttributes(file, BasicFileAttributes.class);
        System.out.println("creationTime     = " + attr.creationTime());
        System.out.println("lastAccessTime   = " + attr.lastAccessTime());
        System.out.println("lastModifiedTime = " + attr.lastModifiedTime());

        System.out.println("isDirectory      = " + attr.isDirectory());
        System.out.println("isOther          = " + attr.isOther());
        System.out.println("isRegularFile    = " + attr.isRegularFile());
        System.out.println("isSymbolicLink   = " + attr.isSymbolicLink());
        System.out.println("size             = " + attr.size());
    }
}

The output of the code snippet:

creationTime     = 2021-05-05T17:09:09.0628061Z
lastAccessTime   = 2021-05-05T17:09:09.0628061Z
lastModifiedTime = 2021-11-04T00:11:43.279Z
isDirectory      = false
isOther          = false
isRegularFile    = true
isSymbolicLink   = false
size             = 0

How do I set file last modified time?

By I Wayan Saryada in Core API, IO 0 Comment

In the following code snippet you will learn how to update file’s last modified date/time. To update the last modified date/time you can use the java.nio.file.Files.setLastModifiedTime() method. This method takes two arguments. The first arguments is a Path object that represent a file, and the second arguments is the modified date in a FileTime object.

Let’s try the code snippet below.

package org.kodejava.io;

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;
import java.nio.file.attribute.FileTime;

public class SettingFileTimeStamps {
    public static void main(String[] args) throws Exception {
        String path = "D:/resources/data.txt";
        Path file = Paths.get(path);

        BasicFileAttributes attr = Files.readAttributes(file, BasicFileAttributes.class);
        System.out.println("lastModifiedTime() = " + attr.lastModifiedTime());

        // Update the last modified time of the file.
        long currentTimeMillis = System.currentTimeMillis();
        FileTime fileTime = FileTime.fromMillis(currentTimeMillis);
        Files.setLastModifiedTime(file, fileTime);

        attr = Files.readAttributes(file, BasicFileAttributes.class);
        System.out.println("lastModifiedTime() = " + attr.lastModifiedTime());
    }
}

The output of the code snippet:

lastModifiedTime() = 2021-05-05T17:09:09.0628061Z
lastModifiedTime() = 2021-11-04T00:11:43.279Z

How do I reverse the order of array elements?

By I Wayan Saryada in Core API, Util Package 0 Comment

In this code snippet you’ll learn how to reverse the order of array elements. To reverse to element order will be using the Collections.reverse() method. This method requires an argument with List type. Because of this we need to convert the array to a List type first. We can use the Arrays.asList() to do the conversion. And then we reverse it. To convert the List back to array we can use the Collection.toArray() method.

Let’s see the code snippet below:

package org.kodejava.util;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class ArrayReverse {
    public static void main(String[] args) {
        // Creates an array of Integers and print it out.
        Integer[] numbers = {0, 1, 2, 3, 4, 5, 6, 7, 8};
        System.out.println("Arrays.toString(numbers) = " +
                Arrays.toString(numbers));

        // Convert the int arrays into a List.
        List<Integer> numberList = Arrays.asList(numbers);

        // Reverse the order of the List.
        Collections.reverse(numberList);

        // Convert the List back to array of Integers
        // and print it out.
        numberList.toArray(numbers);
        System.out.println("Arrays.toString(numbers) = " +
                Arrays.toString(numbers));
    }
}

The output of the code snippet above is:

Arrays.toString(numbers) = [0, 1, 2, 3, 4, 5, 6, 7, 8]
Arrays.toString(numbers) = [8, 7, 6, 5, 4, 3, 2, 1, 0]

How do I use PriorityBlockingQueue class?

By I Wayan Saryada in Concurrency 0 Comment

This example demonstrate how to use the PriorityBlockingQueue class. The PriorityBlockingQueue is one implementation of the BlockingQueue interface. It is an unbounded concurrent queue. The object place in this type of queue must implement the java.lang.Comparable interface. The Comparable interface defines how the order priority of the elements inside this queue.

For simplicity, in this example we use strings object as the elements to be placed in the queue. The String class implements the comparable interface. Running this example will print out the names in the string array in alphabetical orders.

package org.kodejava.util.concurrent;

import java.util.concurrent.BlockingQueue;
import java.util.concurrent.PriorityBlockingQueue;

public class PriorityBlockingQueueExample {
    public static void main(String[] args) {
        final String[] names =
                {"carol", "alice", "malory", "bob", "alex", "jacobs"};

        final BlockingQueue<String> queue = new PriorityBlockingQueue<>();

        new Thread(() -> {
            for (String name : names) {
                try {
                    queue.put(name);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "Producer").start();

        new Thread(() -> {
            try {
                for (int i = 0; i < names.length; i++) {
                    System.out.println(queue.take());
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "Consumer").start();
    }
}

This code print out:

alex
alice
bob
carol
jacobs
malory

How do I use LinkedBlockingQueue class?

By I Wayan Saryada in Concurrency 0 Comment

In the following code snippet you will learn how to use the LinkedBlockingQueue class. This class implements the BlockingQueue interface. We can create a bounded queue by specifying the queue capacity at the object construction. If we do not define the capacity, the upper bound is limited to the size of Integer.MAX_VALUE.

The data in the queue represented as a linked node in a FIFO (First-In-First-Out) order. The head element of the queue is the longest element placed in the queue and the tail element is the latest element added to the queue.

Let’s see the code in action below:

package org.kodejava.util.concurrent;

import java.util.UUID;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;

public class LinkedBlockingQueueExample {
    public static void main(String[] args) {
        final BlockingQueue<String> queue = new LinkedBlockingQueue<>(1024);

        // Producer Tread
        new Thread(() -> {
            while (true) {
                try {
                    String data = UUID.randomUUID().toString();
                    System.out.printf("[%s] PUT [%s].%n",
                            Thread.currentThread().getName(), data);
                    queue.put(data);
                    Thread.sleep(250);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "Producer").start();

        // Consumer-1 Thread
        new Thread(() -> {
            while (true) {
                try {
                    String data = queue.take();
                    System.out.printf("[%s] GET [%s].%n",
                            Thread.currentThread().getName(), data);
                    Thread.sleep(550);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "Consumer-1").start();

        // Consumer-2 Thread
        new Thread(() -> {
            while (true) {
                try {
                    String data = queue.take();
                    System.out.printf("[%s] GET [%s].%n",
                            Thread.currentThread().getName(), data);
                    Thread.sleep(750);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "Consumer-2").start();
    }
}

The output of the code snippet above:

[Producer] PUT [34418601-19cf-41fc-aecc-a0fa7caa72bb].
[Consumer-1] GET [34418601-19cf-41fc-aecc-a0fa7caa72bb].
[Producer] PUT [f2050eaa-c575-4faf-89e8-1ad0e3fbce0e].
[Consumer-2] GET [f2050eaa-c575-4faf-89e8-1ad0e3fbce0e].
[Producer] PUT [2f24985b-009b-44c3-9cec-7a066aa08ecf].
[Consumer-1] GET [2f24985b-009b-44c3-9cec-7a066aa08ecf].
[Producer] PUT [b4332823-c1a2-4587-bf5f-1f67407d6945].
[Consumer-2] GET [b4332823-c1a2-4587-bf5f-1f67407d6945].
[Producer] PUT [33edcd78-1b14-4913-afe2-7f44d76db50b].
[Consumer-1] GET [33edcd78-1b14-4913-afe2-7f44d76db50b].