Java – Convert PNG to JPEG Image File

import java.awt.Color;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;

public class ConvertImageFile {

   public static void main(String[] args) {

	BufferedImage bufferedImage;

	try {

	  //read image file
	  bufferedImage = ImageIO.read(new File("c:\\javanullpointer.png"));

	  // create a blank, RGB, same width and height, and a white background
	  BufferedImage newBufferedImage = new BufferedImage(bufferedImage.getWidth(),
			bufferedImage.getHeight(), BufferedImage.TYPE_INT_RGB);
	  newBufferedImage.createGraphics().drawImage(bufferedImage, 0, 0, Color.WHITE, null);

	  // write to jpeg file
	  ImageIO.write(newBufferedImage, "jpg", new File("c:\\javanullpointer.jpg"));

	  System.out.println("Done");

	} catch (IOException e) {

	  e.printStackTrace();

	}

   }

}

Java – Change File Date / Time using Commons FileUtils

import java.io.IOException;
import org.apache.commons.io.FileUtils;

import java.io.File;

public class Main {

	public static void main(String[] args) {
		try {
			File file = new File("pic.jpg");
			long lastModified1 = file.lastModified();
			FileUtils.touch(file);
			long lastModified2 = file.lastModified();
			System.out.println("File date / time was updated: " + (lastModified2 > lastModified1));
		} catch (IOException ex) {
			ex.printStackTrace();
		}
	}

}

Output:

File date / time was updated: true

Java – Calculate Directory Size using Commons FileUtils

import java.io.File;
import org.apache.commons.io.FileUtils;

public class DirectorySizeSample {

	public static void main(String[] args) {

		// Using FileUtils.sizeOfDirectory() we can calculate
		// the size of a directory including it sub directory
		long size = FileUtils.sizeOfDirectory(new File("C:/Windows"));

		System.out.println("Size: " + size + " bytes");

	}
}

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