The following source code displays a 0 width & height of paper size after calling validatePage for custom paper size.

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import java.awt.*;
import java.awt.print.*;
import java.awt.geom.*;
import javax.swing.*;

public class PlotterTester implements Pageable, Printable{

  private static double PIXELS_PER_INCH = 72.0;
  private static double WIDTH = 17.0; //width of paper in inches
  private static double LENGTH = 24.0; //length of paper in inches
  private static boolean VALIDATE = true;

  private PrinterJob printerJob;
  private PageFormat pageFormat;

  PlotterTester(){
    printerJob = PrinterJob.getPrinterJob();
    createPageFormat();
  }

  private void createPageFormat(){
    pageFormat = new PageFormat();
    Paper p = new Paper();
    double width = WIDTH*PIXELS_PER_INCH;
    double height = LENGTH*PIXELS_PER_INCH;
    double ix = PIXELS_PER_INCH;
    double iy = PIXELS_PER_INCH;
    double iwidth = width - 2.0*PIXELS_PER_INCH;
    double iheight = height - 2.0*PIXELS_PER_INCH;
    p.setSize(width, height);
    p.setImageableArea(ix, iy, iwidth, iheight);
    pageFormat.setPaper(p);
  }

  public Printable getPrintable(int index){
    return this;
  }

  public PageFormat getPageFormat(int index){
    return pageFormat;
  }

  public int getNumberOfPages(){
    return 1;
  }

  private void printPaperSize(PageFormat pf){
    Paper p = pf.getPaper();
    System.out.println("paper size = ("+p.getWidth()+", "+p.getHeight()+")");
  }

  private void printRectangle(Rectangle r){
    System.out.println("("+r.x+", "+r.y+", "+r.width+", "+r.height+")");
  }

  public void print(){
    if(printerJob.printDialog()){
      System.out.println("start printing");
      try{
        printPaperSize(pageFormat);
        if(VALIDATE){
            this.pageFormat = printerJob.validatePage(this.pageFormat);
        }
        printPaperSize(pageFormat);
        printerJob.setPageable(this);
        printerJob.print();
      }catch(Exception e){e.printStackTrace();}
    }
    System.out.println("done printing");
  }

  public int print(Graphics g, PageFormat pf, int pageIndex){
    printRectangle(g.getClipBounds());
    if(pageIndex == 0){
      Graphics2D g2 = (Graphics2D)g;
      Rectangle2D r = new Rectangle2D.Double(PIXELS_PER_INCH, PIXELS_PER_INCH, P
IXELS_PER_INCH, PIXELS_PER_INCH);
      g2.setStroke(new BasicStroke(1.0f));
      g2.draw(r);
      return PAGE_EXISTS;
    }else{
      return NO_SUCH_PAGE;
    }
  }

  public static void main(String[] args){
    System.out.println(System.getProperty("java.version"));
    PlotterTester pt = new PlotterTester();
    pt.print();
    try{
      System.in.read();
    }catch(Exception e){}
    System.exit(0);
  }

}
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