ProgramParameter does not pass value correctly - revisited

A week ago, I posted the below message. Unfortunately, I did not get a
reply. Today, I picked up this problem again. I have done all kinds of
experiments, but again to no avail. I am afraid I will start the weekend
feeling very frustrated. (I'm in Europe, so it's somewhat later here, and
the weekend is about to start, which should normally make me happy.) I
repeat my previous e-mail, hoping this time someone can provide a
solution.

Have a good weekend! (Ok, after all, I think I will enjoy the weekend
too.)

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I am very confused. I want to call a service program from Java. The Java
code looks like this:

public boolean login() throws LoginException {

ServiceProgramCall sPGMCall = null;
AS400 system = null;
AS400Text txtCnv = new AS400Text(10);

try {
ProgramParameter[] parameterList = new
ProgramParameter[1];
parameterList[0] = new
ProgramParameter(txtCnv.toBytes(check_program));
AS400.setPasswordExpirationWarningDays(-1);
system = new AS400(auth_server, user, password);
sPGMCall = new ServiceProgramCall(system);
QSYSObjectPathName fullSrvPgmName = new
QSYSObjectPathName("%LIBL%", "ALSRVWRP", "SRVPGM");
sPGMCall.setProgram(fullSrvPgmName.getPath(),
parameterList);
sPGMCall.setProcedureName("AUTHORIZED_PGM_WRP");
sPGMCall.setReturnValueFormat(ServiceProgramCall.RETURN_INTEGER);
if (sPGMCall.run() != true) {
AS400Message[] messageList =
sPGMCall.getMessageList();
[......]

I copied this setup (defining an AS400Text object, and using method
toBytes on that object to define the parameter) from numerous pages on the
internet. However, when I do a debug on service program ALSRVWRP, all I
see is gibberish (some ASCII characters way out of the normal range).

What on earth is wrong with this code?

Ewout