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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
This noncompliant code example implements a BankOperations class with a removeAccounts() method that is used to terminate all the accounts of a particular account holder, as identified by the name. Names can be repeated in the vector if a person has more than one account. The remove() method attempts to iterate through all the vector entries comparing each entry with the name "Harry".
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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"); // 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", "Harry", "Harry", "Tom"}));
Vector v = new Vector(list);
removeAccount(v, "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", "Harry", "Harry", "Tom"}));
Vector v = new Vector(list);
remove(v,"Harry");
}
}
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Risk Assessment
Using Enumerations when performing remove operations on a vector may cause unexpected program behavior.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
MSC03- J | low | unlikely | medium | P2 | L3 |
Automated Detection
TODO
Related Vulnerabilities
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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