Duplicated string literals make the process of refactoring error-prone, since you must be sure to update all occurrences.
On the other hand, constants can be referenced from many places, but only need to be updated in a single place.
Noncompliant Code Example
With the default threshold of 3:
def foo()
prepare('action random1') #Noncompliant - "action random1" is duplicated 3 times
execute('action random1')
release('action random1')
end
Compliant Solution
def foo()
action1 = 'action random1'
prepare(action1)
execute(action1)
release(action1)
end
Exceptions
To prevent generating some false-positives, literals having 5 or less characters are excluded as well as literals containing only letters, digits
and '_'.