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Unfortunately, a {{Vector}} and an {{Enumeration}} may not always work well together, as demonstrated in the noncompliant code example. In fact, the Java API \[[API 06|AA. Java References#API 06]\] recommends, ""New implementations should consider using {{Iterator}} in preference to {{Enumeration}}."" |
Noncompliant Code Example
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class BankOperations {
private static void removeAccounts(Vector v, String name) {
Enumeration e = v.elements();
while (e.hasMoreElements()) {
String s = (String) e.nextElement();
if (s.equals(name)) {
v.remove("Harry""Harry"); // Second Harry is not removed
}
}
// Display current account holders
System.out.println(""The names are:"");
e = v.elements();
while (e.hasMoreElements()) {
System.out.println(e.nextElement()); // Prints Dick, Harry, Tom
}
}
public static void main(String args[]) {
// List contains a sorted array of account holder names
// Repeats are admissible
List list = new ArrayList(Arrays.asList(
new String[] {"Dick""Dick", "Harry""Harry", "Harry""Harry", "Tom""Tom"}));
Vector v = new Vector(list);
removeAccount(v, "Harry""Harry");
}
}
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Compliant Solution
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According to the Java API \[[API 06|AA. Java References#API 06]\], interface {{Iterator}} documentation: |
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class BankOperations {
private static void removeAccounts(Vector v, String name) {
Iterator i = v.iterator();
while (i.hasNext()) {
String s = (String) i.next();
if (s.equals(name)) {
i.remove(); // Correctly removes all instances of the name Harry
}
}
// Display current account holders
System.out.println(""The names are:"");
i = v.iterator();
while (i.hasNext()) {
System.out.println(i.next()); // Prints Dick, Tom only
}
}
public static void main(String args[]) {
List list = new ArrayList(Arrays.asList(
new String[] {"Dick""Dick", "Harry""Harry", "Harry""Harry", "Tom""Tom"}));
Vector v = new Vector(list);
remove(v,"Harry""Harry");
}
}
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Risk Assessment
Using Enumerations when performing remove operations on a vector may cause unexpected program behavior.
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Search for vulnerabilities resulting from the violation of this rule on the CERT website.
References
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\[[API 06|AA. Java References#API 06]\] Interfaces: Enumeration and Iterator \[[Daconta 03|AA. Java References#Daconta 03]\] Item 21: Use Iteration over Enumeration |
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IDS01-J. Prefer using URIs to URLs 49. Miscellaneous (MSC) MSC04-J. Carefully design interfaces before releasing them