J) for “join” will move the line under the cursor up to the previous line. Note that this also inserts a space at the end of the line. If you type g Shift-j, no space will be appended when joining.
You can join multiple lines at once by highlighting them. For example, gg Shift-v Shift-g Shift-j
ggVGJ will join all lines in the file.
You can refer to
:help join in vim for more information.
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