Java code to achieve screenshot function of screenshot

import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.File;

import javax.imageio.ImageIO;



public class Test
{
 private String fileName; //Prefix of file
 private String defaultName = "GuiCamera";
 static int serialNum=0;
 private String imageFormat; //The format of the image file
 private String defaultImageFormat="png";
 Dimension d = Toolkit.getDefaultToolkit().getScreenSize();

 
 public Test() {
 fileName = defaultName;
 imageFormat=defaultImageFormat;

 }

 
 public Test(String s,String format) {

 fileName = s;
 imageFormat=format;
 }

 
 public void snapShot() {

 try {
 //Copy the screen to a BufferedImage object screenshot
 BufferedImage screenshot = (new Robot()).createScreenCapture(new
 Rectangle(0, 0, (int) d.getWidth(), (int) d.getHeight()));
 serialNum++;
 //File names are automatically generated based on file prefix variables and file format variables
 String name=fileName+String.valueOf(serialNum)+"."+imageFormat;
 File f = new File(name);
 System.out.print("Save File "+name);
 //Write the screenshot object to the image file
 ImageIO.write(screenshot, imageFormat, f);
 System.out.print("..Finished!n");
 }
 catch (Exception ex) {
 System.out.println(ex);
 }
 }

 public static void main(String[] args)
 {
 Test cam= new Test("d:\Hello", "png");//

 cam.snapShot();
 }
}