How to capture a screenshot using Java and save it to a file?

A screenshot, screen capture, or screen dump is an image taken by the computer to record the visible items displayed on the monitor or another visual output device. Usually this is a digital image taken by the host operating system or software running on the computer device, but it can also be a capture made by a camera or a device intercepting the video output of the computer.

Screenshots, screen dumps, or screen captures can be used to demonstrate a program, a particular problem a user might be having or generally when computer output needs to be shown to others or archived, or to simply show off what you do on your computer to others. [Wikipedia]

The following java program demonstrates how to use Robot class from java.awt package to capture screenshots and save the image thus captured to disk.

package com.kushal.utils;

/**
 * @author Kushal Paudyal
 * JavaScreenCaptureUtil.java
 * 
 * This utility captures the screenshot and saves
 * the captured image to disk.
 */
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Calendar;

import javax.imageio.ImageIO;

public class JavaScreenCaptureUtil {

	public static void main(String args[]) throws Exception {

		/**
		 * This class (Robot.java) is used to generate native system input events for the 
		 * purposes of test automation, self-running demos, and other 
		 * applications where control of the mouse and keyboard is needed. 
		 * The primary purpose of Robot is to facilitate automated testing 
		 * of Java platform implementations. 
		 */
		Robot robot = new Robot();
		
		/**
		 * Get the current screen dimensions.
		 */
		Dimension d = new Dimension(Toolkit.getDefaultToolkit().getScreenSize());
		int width = (int) d.getWidth();
		int height = (int) d.getHeight();
		
		
		/**
		 * Delay the robot for 5 seconds (5000 ms) allowing you to switch to proper
		 * screen/window whose screenshot is to be taken.
		 * 
		 * You can change the delay time as required.
		 */
		robot.delay(5000);
		
		/**
		 * Create a screen capture of the active window and then create a buffered image
		 * to be saved to disk.
		 */
		Image image = robot.createScreenCapture(new Rectangle(0, 0, width,
				height));

		BufferedImage bi = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);
		Graphics g = bi.createGraphics();
		g.drawImage(image, 0, 0, width, height, null);

		/**
		 * Filename where to save the file to.
		 * I am appending formatted timestamp to the filename.
		 */
		String fileNameToSaveTo = "C:/temp/screenCapture_"
				+ createTimeStampStr() + ".PNG";
		
		/**
		 * Write the captured image to a file.
		 * I am using PNG format. You can choose PNG, JPG, GIF.
		 */
		writeImage(bi, fileNameToSaveTo, "PNG");

		System.out.println("Screen Captured Successfully and Saved to:n"+fileNameToSaveTo);

	}

	/**
	 * This method writes a buffered image to a file
	 * 
	 * @param img -- > BufferedImage
	 * @param fileLocation --> e.g. "C:/testImage.jpg"
	 * @param extension --> e.g. "jpg","gif","png"
	 */
	public static void writeImage(BufferedImage img, String fileLocation,
			String extension) {
		try {
			BufferedImage bi = img;
			File outputfile = new File(fileLocation);
			ImageIO.write(bi, extension, outputfile);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	/**
	 * 
	 * @return String representation of timestamp 
	 * in the format of yyyyMMdd_hhmmss (e.g. 20100426_111612)
	 * @throws Exception
	 */
	public static String createTimeStampStr() throws Exception {
		Calendar mycalendar = Calendar.getInstance();
		SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMdd_hhmmss");
		String timeStamp = formatter.format(mycalendar.getTime());

		return timeStamp;

	}

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}