Figure out the logic first. I would do something like:
On row 0 I want 1 star
On row 1 I want 2 stars
on row 2 I want 3 stars
...
on row x I want (x + 1) stars
...
stop at row y.
Then translate that into pseudo code
begin loop that will loop y times.
print (loop index + 1) stars
print new line
end loop
That line "print loop index + 1 stars can be further broken down into its own loop.
begin loop that will loop y times.
// print (loop index + 1) stars
create an inner loop that loops from 0 to the current (outer loop's index + 1)
print a "*"
end inner loop
print new line
end loop
Now you try to translate the pseudo-code into Java code.