How to have input-redirection with Javas ProcessBuilder?

How can I apply input redirection to Javas ProcessBuilder?

E.g. use cat of Linux

cat x.txt > output.txt

My code

// read x.txt with cat and redirect the output to output.txt
public static void main (String args []) throws Exception
{
    List <String> params = new ArrayList <String> ();
    params.add ("cat");
    params.add ("x.txt");       
    ProcessBuilder pb = new ProcessBuilder (params);
    pb.redirectOutput (new File ("output.txt"));
    Process p = pb.start ();
    p.waitFor (3, TimeUnit.SECONDS);
    System.out.println ("exit="+p.exitValue());
}

That works fine!
But how to change from file to input-redirection?

cat << END > output

I tried this – but does not work.

public static void main (String args []) throws Exception
{
    List <String> params = new ArrayList <String> ();
    params.add ("cat");
    params.add ("/dev/stdin");
    params.add ("<<";
    params.add ("END");
    
    ProcessBuilder pb = new ProcessBuilder (params);
    pb.redirectOutput (new File ("output.txt"));
    Process p = pb.start ();
    OutputStream os = p.getOutputStream ();
    os.write ("\nblabla\nEND\n".getBytes ());
    p.waitFor (3, TimeUnit.SECONDS);
    System.out.println ("exit="+p.exitValue());
}

No matter what I tried it returned with 1 (instead of 0 for success) or did not finish.