Why is this an issue?

Using upper case literal suffixes removes the potential ambiguity between "1" (digit 1) and "l" (letter el) for declaring literals.

Noncompliant code example

long long1 = 1l; // Noncompliant
float float1 = 1.0f; // Noncompliant
double double1 = 1.0d; // Noncompliant

Compliant solution

long long1 = 1L;
float float1 = 1.0F;
double double1 = 1.0D;

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