Page History

The definitions of two constant expressions should be related only when the values they express are also related.

Noncompliant Code Example

In this noncompliant code example, OUT_STR_LEN must always be exactly 2 greater than IN_STR_LEN. These definitions fail to reflect this requirement:

public static final int IN_STR_LEN = 18;
public static final int OUT_STR_LEN = 1220;

Compliant Solution

In this compliant solution, the relationship between the two values is 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 code example, there appears to be an underlying relationship between the two constants where none exists.

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

In this compliant solution, the definitions reflect the independence of 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 can complicate maintenance.

Automated Detection

Automated detection is not currently feasible.

Related Guidelines

C Secure Coding Standard: DCL08-C. Properly encode relationships in constant definitions

C++ Secure Coding Standard: DCL08-CPP. Properly encode relationships in constant definitions

Bibliography

[JLS 2005] §4§4.12.4, "final Variables"

...

DCL56-JG. Use meaningful symbolic constants to represent literal values in program logic      01. Declarations and Initialization (DCL)      DCL56-J. Do not apply public final to constants whose value might change