Avoid Enumeration For Loop Control

ID

java.loop_legacy_enumeration

Severity

info

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Best Practice

Language

Java

Tags

efficiency

Description

Reports the use of java.util.Enumeration as the driver of a while or do-while loop — the classic while (e.hasMoreElements()) { e.nextElement(); } pattern.

Rationale

Enumeration predates the Collections framework and has been superseded in practical code by Iterator and Iterable:

  • it is not Iterable, so it cannot be used with the enhanced for-each loop;

  • it does not support element removal (Iterator.remove());

  • method names (hasMoreElements, nextElement) are verbose compared with the idiomatic hasNext/next.

Most Enumeration-returning APIs expose an iterator() or a collection view. Using them lets the loop participate in standard idioms — for-each, forEachRemaining, streams.

// Bad — legacy Enumeration drives the loop
Enumeration<String> e = vector.elements();
while (e.hasMoreElements()) {
    process(e.nextElement());
}

// Good — enhanced for-each over the collection
for (String s : vector) {
    process(s);
}

// Good — Iterator when removal is needed
Iterator<String> it = vector.iterator();
while (it.hasNext()) {
    if (isStale(it.next())) {
        it.remove();
    }
}

Remediation

Replace the Enumeration with an Iterator (via Collection.iterator()) or iterate directly with for-each when the receiver is Iterable. For legacy APIs that only expose Enumeration (e.g. NetworkInterface.getInetAddresses()), wrap it with Collections.list(…​) and iterate the resulting list.

References