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Floating-point variables must not be used as loop counters. Limited-precision IEEE 754 floating-point types cannot represent

• all All simple fractions exactly.
• all All decimals precisely, even when the decimals can be represented in a small number of digits.
• all All digits of large values, meaning that incrementing a large floating-point value might not change that value within the available precision.

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This compliant solution uses an integer loop counter from which the desired floating-point value is derived.:

for (int count = 1; count <= 10; count += 1) {
  float x = count/10.0f;
  System.out.println(x);
}

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This noncompliant code example uses a floating-point loop counter that is incremented by an amount that is typically too small to change its value given the precision.:

for (float x = 100000001.0f; x <= 100000010.0f; x += 1.0f) {
  /* ... */
}

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This compliant solution uses an integer loop counter from which the floating-point value is derived. Additionally, it uses a double to ensure that the available precision suffices to represent the desired values. The solution also runs in strict floating-point (FP-strict) mode to guarantee portability of its results . See (see NUM53-J. Use the strictfp modifier for floating-point calculation consistency across platforms for more information).

for (int count = 1; count <= 10; count += 1) {
  double x = 100000000.0 + count;
  /* ... */
}

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Automated Detection

Automated detection of floating-point loop counters is straightforward.

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Bibliography

[Bloch 2005]	Puzzle 34. , "Down for the countCount"
[JLS 2005]	§4§4.2.3, Floating-Point Types, Formats, and Values
[Seacord 2015]	NUM09-J. Do not use floating-point variables as loop counters LiveLesson

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