DCL03-J. Properly encode relationships in constant definitions

The definitions of two constant expressions should be related if and only if the values they are expressing are also related.

Noncompliant Code Example

In this noncompliant code example, OUT_STR_LEN must always be exactly two greater than IN_STR_LEN. However, this is not obvious from the definitions.

public static final int IN_STR_LEN = 18;
public static final int OUT_STR_LEN = 20;

Compliant Solution

Instead, the relationship between the two values should be represented in the definitions.

public static final int IN_STR_LEN = 18;
public static final int OUT_STR_LEN = IN_STR_LEN + 2;

Noncompliant Code Example

In this noncompliant example, there appears to be an underlying relationship between the two constants, but there is none.

public static final int ADULT_AGE = 18;
public static final int ALCOHOL_AGE = ADULT_AGE + 3;

A programmer performing routine maintenance may modify the definition for ADULT_AGE but fail to recognize the resulting change in the definition for ALCOHOL_AGE.

Compliant Solution

Instead, the definitions should reflect the lack of a relationship between the two constants.

public static final int ADULT_AGE = 18;
public static final int ALCOHOL_AGE = 21;

Risk Assessment

Failure to properly encode relationships in constant declarations can lead to unexpected values and produce code that is difficult to maintain.

Other Languages

This rule appears in the C Secure Coding Standard as DCL08-C. Properly encode relationships in constant definitions.
This rule appears in the C++ Secure Coding Standard as DCL08-CPP. Properly encode relationships in constant definitions.

Related Vulnerabilities

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

References

[JLS 2005] Section 4.12.4

DCL02-J. Use meaningful symbolic constants to represent literal values in program logic      03. Declarations and Initialization (DCL)      DCL04-J. Declare mathematical constants as static and final