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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