Question

Can I set the default arument value in Construct function something like
?

public class XLSReader {
  public XLSReader(String filename="XYZ.xls") {
  }
}

Answer 1

No. Java doesn’t support optional parameters. You can use overloading and chaining though:

public XlsReader() {
    this("XYZ.xls");
}

public XlsReader(String filename) {
    // Use filename here
}

(This applies to methods as well as constructors.)