在PrintRequestAttributeSet中添加打印机名称时出现ClassCastException

Question

我在执行打印机程序时遇到异常。是否有任何其他方法可以指定未在系统中配置的网络打印机。

  

线程“main”中的异常java.lang.ClassCastException at   javax.print.attribute.AttributeSetUtilities.verifyAttributeValue（AttributeSetUtilities.java:552）     在   javax.print.attribute.HashAttributeSet.add（HashAttributeSet.java:304）     在com.printing.PrintingService.main（PrintingService.java:118）

代码

public static void main(String [] a) throws FileNotFoundException, PrintException {
    String text = " My first Printer Program";

    InputStream fis = new ByteArrayInputStream(text.getBytes());
    if (fis == null) 
    { 
        System.out.print("No File");
        return; 
    } 
    DocFlavor flavor = DocFlavor.INPUT_STREAM.AUTOSENSE;
    PrintRequestAttributeSet aset = new  HashPrintRequestAttributeSet();

    PrintService[] service = PrintServiceLookup.lookupPrintServices(flavor, aset);
    aset.add(new PrinterName("ipp://abcd.com/ipp/ITDepartment-HP4050", null)); ///// throwing exception on this line :ClassCastException

    if (service != null){
        System.out.println("Printer: " + service[0].getName());

        DocPrintJob job = service[0].createPrintJob();
        try{
            Doc doc = new SimpleDoc(fis,flavor,null);
            job.print(doc,aset);
            fis.close();
        }
        catch(Exception e) {
            System.out.println(e);
        }

    }
}