The short answer to your question is that the Dutch East India Company introduced coffee to Indonesia, began to cultivate it on the island of Java, and then imported this Javanese coffee into Europe in large amounts, controlling 50-70% of global coffee production during the second half of the eighteenth century (Kahin 2015:97). The history of the rise of Indonesian coffee can be traced, but the reason for the popularity of the slang “Java” has to be inferred.

In 1614, Dutch traders visited Yemen to explore the possibility of importing coffee to Europe. Reportedly, no fertile coffee berries were allowed to leave Yemen unless they had first been steeped in boiling water or partially roasted. So, they were the sole, or at least primary, source of imported coffee – even coffee in Turkey had been imported from Yemen.

In 1640, a Dutch merchant imported the first commercial shipment of coffee from Mocha to Europe, and regular imports of coffee from Mocha to Amsterdam began in 1663.

With the growing popularity of coffee in Europe, there were repeated attempts to find ways to grow it elsewhere. A frequently quoted (but possibly apocryphal) story claims that an Indian Muslim named Babu Budan smuggled seven seeds back from his pilgrimage to Mecca by "strapping them to his belly." He is then said to have planted these seeds in the Changraigiri Hills which gave rise to India's coffee industry. There is, however, no documentary evidence for this and the first mention of coffee in India is in 1695, so it is unlikely that this had a dramatic impact on coffee cultivation. (Wild, 1995: 98-100)

One account (Ukers 1922:43) is that the Dutch transplanted Arabian coffee seedlings to Java in 1696. They were destroyed by flooding, but a second shipment sent in 1699, succeeded. A second (Pendergrast 1999: 7-9) is that in 1616 the Dutch obtained a coffee plant from Mocha or possibly Ethiopia (Abyssinia). The plants were transported to the botanical garden in Amsterdam, and seeds from it were sent to Ceylon in 1658, perhaps with the intent of starting production there. The initiative failed (possibly due to a lack of manpower). Finally however, the coffee plantations in Java were established in 1699 with cuttings from Dutch plants from Malabar, India.

Once coffee had been transplanted in Java, the Dutch Company was able to begin cultivation and importation on a large scale. As Dutch cultivation intensified, coffee in Europe was increasingly from Java and the nickname began to develop. [Except the Dutch apparently gave the French King a specimen of the coffee plant, which was then transplanted to French colonies undercutting the Dutch supply.] An additional reason for its use in American English is that early importers of coffee into America were Dutch transplants from the Indies. Alfred Peet, for example, who founded Peet’s Coffee and trained the founders of Starbucks, was a Dutchman who worked as a tea taster in the Indies (now Indonesia). Though it is hard to prove definitively, these pioneers of specialty coffee in America may have fostered the association between coffee and Indonesia (Java).

Sources:

Audrey Kahin, Historical Dictionary of Indonesia (Rowman & Littlefield, 2015)

Jati Misnawa, "Indonesia" in Coffee: A Comprehensive Guide to the Bean, the Beverage, and the Industry, eds. Robert W. Thurston, Jonathan Morris, Shawn Steiman (Rowman & Littlefield Publishers, 2013).

Mark Pendergrast, Uncommon Grounds (Basic Books, 1999).

William Harrison Ukers, All About Coffee (The Tea and Coffee Trade Journal Company, 1922).

Antony Wild, Coffee: A Dark History (W. W. Norton & Company, 2005)

Does "strong" to you mean flavor? or amount of caffeine? I always have to not go too far, or else I'll get too bitter. But in general to get "stronger" coffee: (1) longer brew time (2) finer grind (3) less coffee.

And for "Less" vs. "More" I personally change via a scale since 2T of one coffee may weigh less than 2T of another due to grind and water content in the beans, etc.

Does the interface contain a toastring method?