就 (like many other Chinese characters) has more than one meaning. So it can be used in many different ways. When you use 一 and 就 together, it means "as soon as.." for example 我一来他就走了 - as soon as I came, he left. 就 can also be used to show that something happens or has happened early: 我下午三点就到机场了 - I arrived at the airport [as early] as 3pm. note that when you use "就" in this sense, 了 must also be used (to show the completion) "就“ can also mean "only/just". For example if someone asks you "要喝几杯?" (how many cups would you like?) you can answer 就一杯(just one). There are also other ways 就 can be used! Make sure you pay attention to how it is being used ! :)

[verb] come near；move towards；go to；take up 就着灯看书。各就各位! [prep] with regard to；concerning 就事论事 [adv] at once；right away；as early as；already 我就来。雨早上就停了。 [conj] even if 就算她来，也晚了

我就不。means that although I know the reason of the thing you ask me to do, I still don't want to do it. but it's a little unpolite.

i search five sentences from baidu,i hope these sentences can help you; 1.所以她就这么一走了之？(So she just left?) 2.只需加上热水搅动就行。(Simply add hot water and stir.) 3.国会就这个问题分组表决。(Parliament divided on the question.) 4.我一开始就起疑心。(I suspected something right away.) 5.要是我能飞就好了。(If only I could fly)