OBJ13-J. Do not use public static final mutable objects

Exposing a public static final object allows clients to modify the contents of the object (although they will not be able to change the object itself, as it is final). 

Noncompliant Code Example

public static final SomeType [] SOMETHINGS = { ... };

With this declaration, SOMETHINGS[1], etc. can be modified by clients of the code.

Compliant Solution

One approach is to have a private array and a public method that returns a copy of the array:

private static final SomeType [] SOMETHINGS = { ... };
public static final SomeType [] somethings() {
  return SOMETHINGS.clone();
}

Now, the original array values cannot be modified by a client.

Compliant Solution 2

An alternative approach is to have a private array from which a public immutable list is contructed:

private static final SomeType [] THE_THINGS = { ... };
public static final List<SomeType> SOMETHINGS =
  Collections.unmodifiableList(Arrays.asList(THE_THINGS));

Now, neither the original array values nor the public list can be modified by a client.

Risk Assessment

Having a public static final array is a potential security risk, as the array elements may be modified by a client.

Automated Detection

TODO

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this guideline on the CERT website.

References

[JLS 2006] Section 6.6, Access Control
[Bloch 2008] Item 13: Minimize the accessibility of classes and members

SEC36-J. Ensure that the bytecode verifier is applied to all involved code upon any modification      09. Platform Security (SEC)      01. Declarations and Initialization (DCL)