Use Integer Index Variable in Loops

ID

java.loop_integer_index

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Java

Tags

best-practice, reliability

Description

Reports for-loops whose index variable is declared with a non-integer type such as long, double, or float.

Rationale

Array indices in Java must be int. Using a long index variable may cause silent truncation when used as an array index. Floating-point index variables (float, double) suffer from rounding errors that can cause off-by-one iteration counts or infinite loops.

// Bad - long index may truncate when used as array index
for (long i = 0; i < arr.length; i++) {
    System.out.println(arr[(int) i]);
}

// Bad - floating-point rounding may skip or repeat iterations
for (double d = 0; d < 10; d++) {
    System.out.println(d);
}

Remediation

Use int for loop index variables.

// Good
for (int i = 0; i < arr.length; i++) {
    System.out.println(arr[i]);
}

References