Catch-22 was published 1961. The author was born in 1923 and died in 1999.
http://www.gutenberg.net.au/birthdeath.html:
Under Australian copyright law, literary, dramatic, & musical work published, performed, communicated, or recorded and offered for sale in an author's lifetime are, where the author died in or before 1954, protected for the life of the author plus fifty years from the end of the year of the author's death. For authors who died in or after 1955 works are protected for the life of the author plus seventy years from the end of the year of the author's death. After this time they enter into the public domain in Australia.
So, it will become public domain material in Australia at the end of 2069.