After a period of exposure to European interests, Japan secluded itself in the 1630s. George Lensen wrote in "The Russian Push Towards Japan":
On the eve of her seclusion, Japan had begun to expand into southeast Asia and her countrymen had made their way to the Philippines, Annam, Siam, and Java, establishing flourishing colonies there. But her voluntary isolation had compelled Japan not only to restrict her territorial expansion, but to scuttle her naval efforts, and to discontinue the construction of big seagoing vessels.
How substantial were those Japanese colonies and how long did they last? Were they primarily trading posts or attempts at administering territory? Java is much farther south than the other locations cited, so why was it a destination?