Q:

java.nio.file can not copy files

Very simple file copy, both directories are exist, got below message:
Code--
  import java.nio.file.Files;
  import java.nio.file.Paths;
  import static java.nio.file.StandardCopyOption.*;

  Files.copy(
      Paths.get("/u/isciw2/reposi1/ISCIW batch/20170821-3927/packageManifest.xml"), 
      Paths.get(" /PXAS61/usr/lpp/ucd/V6.2.1/var/work/ISCIW  batch/546b3d10-0256-4bcd-9d3c-504ca31714d5/20170821-3927/packageManifest.xml"),
      REPLACE_EXISTING);

ERROR-- Caught: java.nio.file.NoSuchFileException: 
  /PXAS61/usr/lpp/ucd/V6.2.1/var/work/ISCIW
  batch/546b3d10-0256-4bcd-9d3c-504ca31714d5/20170821-3927/packageManifest.xml
  java.nio.file.NoSuchFileException: 
  /PXAS61/usr/lpp/ucd/V6.2.1/var/work/ISCIW
  batch/546b3d10-0256-4bcd-9d3c-504ca31714d5/20170821-3927/packageManifest.xml
    at
  groovy_script_3470154301378281065.run(groovy_script_3470154301378281065.groovy:20)

A:

On UNIX, copy and paste your paths into commands like:
$ ls "/PXAS61/usr/lpp/ucd/V6.2.1/var/work/ISCIW batch/546b3d10-0256-4bcd-9d3c-504ca31714d5/20170821-3927/packageManifest.xml"

... ensuring that the quotes and the spaces appear exactly as they do in your Java.
I would expect you to get an error response like:
ls: cannot access /PXAS61/usr/lpp/ucd/V6.2.1/var/work/ISCIW batch/546b3d10-0256-4bcd-9d3c-504ca31714d5/20170821-3927/packageManifest.xml: No such file or directory

... in which case Java and ls agree: this file doesn't exist.
Now find the actual file, and adjust the ls command until it doesn't error. Once it works, you can copy/paste the correct path into your Java.
As a short cut (assuming the base of the path is correct), you could find candidate correct paths with something like:
$ find /PXAS61/usr/lpp/ucd -name packageManifest.xml

... or even, on many systems:
$ locate packageManifest.xml

