Returning MIN_VALUE From compareTo()

java.compareto_min_value

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Java

Description

Reports return Integer.MIN_VALUE (or Long.MIN_VALUE) inside compareTo() methods. Negating MIN_VALUE overflows back to MIN_VALUE, which breaks any code that computes -compareTo() to reverse sort order.

Rationale

Integer.MIN_VALUE is -2147483648. Its negation overflows to itself: -Integer.MIN_VALUE == Integer.MIN_VALUE. Sorting algorithms, Comparator.reversed(), and manual sign-flipping all rely on -compareTo() yielding the opposite sign. When compareTo() returns MIN_VALUE, this invariant is violated.

// Bad - negation overflows
public int compareTo(Foo other) {
    if (this.x < other.x) return Integer.MIN_VALUE;
    return 0;
}

Remediation

Return -1, 0, or 1, or use Integer.compare().

// Good
public int compareTo(Foo other) {
    return Integer.compare(this.x, other.x);
}

References

Comparable