I am not an expert on China, and can't say much about Chinese sea-faring. I can however correct a few misconceptions here.

Indigenous Australians first discovered Greater Australia at least 60,000 years ago.

Visits from Austronesian seafarers in the last 1000 years are likely, evidenced by the introduction of the dingo and the difference in languages in northern Australia.

The people of the Torres Strait Islands had constant contact with New Guinea and northern Cape York.

Visits by Indonesians are likely but unconfirmed until much later (starting in the late 1600s). These were Makassan fishermen from Sulawesi, who harvested sea cucumber for the Chinese market.

Visits by the Spanish and Portuguese around the late 1500s are also likely but unconfirmed. The first confirmed non-Indigenous visitor to Australia is the Dutchman Willem Janzsoon, who landed in Cape York in 1606 just months before the Spanish Luis Vaz de Torres sailed the strait between New Guinea and Australia.

Five years later the Dutch pioneered the Brouwer route across the Indian Ocean (a faster but less predictable route to Indonesia), which elicited a flurry of Dutch explorers and shipwrecks on Australia's coasts, with their last voyage of discovery by Abel Tasman in 1644 revealing all but the east coast of Australia and the Bass Strait. Other important events include the horrific Batavia Disaster, and Willem de Vlamingh's voyage up the Swan River in 1697.

The first English explorer was William Dampier in 1699, after nearly a century of Dutch exploration of Australia. His books inspired many English navigators, including James Cook and Joseph Banks.

The Chinese may have visited in the early 1400s during Zheng He's great expeditions, but there is no evidence for this. It would also be unlikely to have changed Australian history much, beyond some local variation in Indigenous culture - the only visitors to bring significant change to Australia prior to British invasion were the Makassans, who maintained centuries of return visits, face-to-face interactions and coastal activity.

Good books to read on this are: The First Footprints by Scott Cane, discussing prehistoric Indigenous Australia (also has a great documentary version showcasing amazing art and locations)

The Savage Shore by Graham Seal, which looks at the voyages of European maritime explorers and discusses possible visitors as well.