Fire-hardened spears, hardwood clubs and maces and shark-tooth "swords" were pretty much state-of-the-art for both Aboriginal and Polynesian cultures.
The Polynesians had the advantage of advanced stonemasonry and oceanic navigation, neither of which would do them much good in a war of conquest, the native Australians had a spear-thrower, the woomera, which vastly improves the range and power of a thrown spear.
More, Polynesian wars were mostly local affairs, precipitated by cultural conflicts and resource allocation rather than wars of conquest.
The Europeans had steel, gunpowder, horses and ships capable of carrying immense loads of cargo and troops, and a will to conquer and claim anything they found.
Completely different ballgame.
As for Austronesian people, like Indonesians, it is difficult to answer.
I can really only speculate: The trade winds were very strongly against them (see: this map )
The Maritime SE Asian cultures really only interacted with others from the same culture group, unless for trade Australians and New Guineans of the time had neither spices nor mineral or metal goods, so trade missions (and perhaps colonies) were considered futile.
history.stackexchange.com/users/892/RI Swamp Yankee
People from what is modern day Indonesia were visiting northern Australia to collect and process trepang (sea-cucumber or sea slug) for centuries before European settlement.
These people are generally referred to as Macassan (or Makassan).
The first European to circumnavigate Australia, Matthew Flinders, encountered Macassans processing trepang.
Relationships with the Aboriginal people were mostly positive as the Macassans stayed for a few months per year and returned home as the winds changed to trade their product with the Chinese.
This information has been extensively documented Gordon McLaughlan claims that pre-Moari Polynesian navigators (referred to as Lapita) "landed on the coast of Australia but encountered an alien landscape and long-established inhabitants" (p.18 - A Short History of New Zealand - Penguin, 2004).
I have no idea as to whether this claim is supported by the historical record or whether it is simply an assumption based on the incredible sea-faring exploits of the Lapita.
history.stackexchange.com/users/2983/Arak
Australia was a lot less hospitable area than Polynesians, Indonesians, and other islanders were used to.
Although technically in the tropics, the fact that people lived on islands meant that the sea was a moderating influence on the climate, and "temperate" weather crops such as breadfuirt and sweet potatoes could grow on them.
Also, the sea provided a ready source of fish.
http://en.wikipedia.org/wiki/Polynesia
Not so Australia, which being continental, had a less temperate climate.
Jungles were thicker, crops scarcer, and food harder to find.
As mentioned in other answers above, the "Australians" had more potent weapons, probably because of the need to hunt mammals, rather than fish.
It's possible that Pacific Islanders found themselves in Australia from time to time.
Most probably did not survive.
Perhaps a few survivors were absorbed into the local populations.
What did NOT happen was people visiting Australia, leaving, and then saying, "Let's go back there with the friends and family.
history.stackexchange.com/users/120/Tom Au
I can only agree with some of the points, as I have an extensive understanding of Austronesian migratory history but am still vague on Australasian.
My only contribution is to add that Australia was not so much a lost continent but rather a vast and imposing one which was not entirely cut of from southern migration.
It was part of PNG during the ice age and the two land masses share a common genus.
Migrants still continued to flow in to Australia but in small groups who simply blended into the existing population.
In the southern regions there is evidence that many of the aboriginal population have cultural and ethnic ties to their Southern roots as fishermen and canoe building coastal communities.
However Lapita and other Austronesian's were strictly a island colonizing coastal peoples who had specific destinations in mind, isolated unpopulated small land masses which they could farm and colonize.
Culturally
and ethnically they integrated with existing trading communities such as PNG and probably the southern western coastal parts of Australia but a large land mass
had very little appeal to their mindset.
Obviously, groups in Indonesia were trading and taking resources from coastal Australia but were more interested in their own regional concerns and had no particular drive to colonize this harsh and seemingly desolate interior that was probably inhabited by territorial tribal groups of people.
It seems strange to me that such a small divide between Indonesia and Australia would have such little momentum in terms of their contact but little was coming out of Australia as opposed to the vast trade network that had formed from the Southern trade roots and their spice empires.
It's not so much about land as trade it would seem, which makes sense but perhaps more historical evidence will be discovered.
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The austronesian were great mariners and this brought them to far corner of the globe as far as Easter island and Madagascar.
But why not Australia which lies south of Indonesia?
I think the most plausible answer is because its already inhabited and when austronesian made landings, to Australia, it was by chance and composed of a handful of individuals.
They stood little chance against the hostile aborigines even if they possessed superior weaponry.
Furthermore Australia is a large island, any subsequent waves of chance landings would have occurred far apart from each others and not making it possible for the austronesian to form meaningful numbers to compete against the aborigines as compared to uninhibited islands.
These earlier austronesian would have been outnumbered and decimated.
history.stackexchange.com/users/1518/Sim
I agree that scattered Austronesian landings on the big island continent may well have prevented this culture from building up any significant numbers to thrive.
But I don't think it would be due to any hostility of Aborigines that they wouldn't.
I'd say that the locals would expect some sort of compensation like seafood, for the imposition on their lands, and this kind of arrangement over time could have lead to intermarriages and the Austronesians blending in with the aborigines.
Future DNA studies may be able to answer this.
history.stackexchange.com/users/6929/Lincoln Jackson
Australia was colonised by people from New Guinea while the two islands were still joined (up to 25,000 years ago).
Evidence of human habitation in eastern New Guinea dates back to 40,000 years.
The negroid ie small frizzy haired people were the first Australians.
Their remnants can be found in the rainforests of northern Queensland and in Tasmania.
history.stackexchange.com/users/3901/jim morris
Australia hosted aboriginal populations since prehistory. However technologically advanced civilizations (in comparison) lived nearby, in Indonesia, Polynesia and New Guinea.  Why was it not colonized by those people? Is there any evidence of interaction/invasions?
Why did Austronesian/Polynesian people not colonize Australia?
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<colonization><australia><south-east-asia>
history.stackexchange.com/questions/4381
history.stackexchange.com/users/1436/astabada
There may well have been landings from time to time but the country is so large that it prevented groups from forming. People from Indonesia practiced sea cucumber fishing in northern Australia for centuries before European settlement. They had no particular drive to colonise and had their own, local concerns. Australia was also very inhospitable compared to other parts of Asia. The answer to this question will be subjective, but there are a number of reasons that Polynesian peoples didn't colonise Australia. Firstly, they were unlikely to have had sufficient numbers to make a successful colonisation attempt. Furthermore, there didn't seem to be much in terms of trade or anything enticing to encourage them to make a colonisation effort. As a side note, it seems there is evidence of New Gineau colonisation of Australia, but this would have been around 25,000 years ago.
Whilst its possible that the Pacific Islanders found themselves in Australia, the main reason that they are unlikely to have attempted to colonise it would be a lack of numbers. There is plenty of evidence of trade between the Pacific Islanders, Indonesia and Australia. There is evidence of colonisation by people from New Guinea over 25,000 years ago. It seems that there was very little enticing other nearby civilisations to colonise Australia given the lack of trade and the hostility of the continent.