Float or Double Loop Counter

ID

java.float_loop_counter

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Java

Tags

reliability

Description

Reports for-loops whose counter variable is declared as float or double. Floating-point arithmetic is subject to rounding errors, which can cause the loop to iterate one too many or one too few times.

Rationale

Floating-point values cannot represent all decimal fractions exactly. Incrementing 0.0f by 0.1f ten times does not yield exactly 1.0f, so a loop condition f < 1.0f may behave unexpectedly.

// Bad - may iterate 9 or 11 times instead of 10
for (float f = 0.0f; f < 1.0f; f += 0.1f) {
    process(f);
}

Remediation

Use an integer counter and compute the floating-point value inside the loop body.

// Good - precise iteration count
for (int i = 0; i < 10; i++) {
    float f = i * 0.1f;
    process(f);
}

References