in eclipse, on the bottom bar of the ide, there is a number like: 1:1, 19:20, 50:100… this means that “line:charactersinline”.
to complement not exceed too much the number of characters in line is a good practice. i’m the old days programming with very little monitors on resolution with 800×600, the number of 80 characters was a good one. but now with widescreen monitors a good number of characters in accord with many programmers is 120 characters per line.
complementing the answer of @david kaczynski:
i found it. go to windows -> preferences. select text editors in the dialog box, and check the “show print margin” option. this will display a marker at a given column number that can allow the author to avoid exceeding a specific line length.
after you activated show print margin that shows the count of the lines, you can configure to:
print margin column: 120
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