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Literals that describe mathematical constants are often used to represent well established constants. This eliminates the need to use their actual values throughout the source code and reduces the possibility of committing frivolous errors. (See Guideline DCL02-J. Use meaningful symbolic constants to represent literal values in program logic for more information.)

If a mathematical constant is not declared static, every instance of the class object will needlessly retain its own copy of the constant. Moreover, failing to declare a constant field final can be counterproductive, as highlighted in guideline OBJ03-J. Do not use public static non-final variables. Disregarding this advice can expose the constants to pernicious thread safety issues.

At the same time, the use of {{static-final}} modifiers should not be abused. According to the Java Language Specification \[[JLS 2005|AA. Java References#JLS 05]\], sectionSection 13.4.9, "{{final}} Fields and Constants": 

Other than for true mathematical constants, we recommend that source code make very sparing use of class variables that are declared static and final. If the read-only nature of final is required, a better choice is to declare a private static variable and a suitable accessor method to get its value.

Furthermore, when read only access is required, it recommends the following:

private static int N;
public static int getN() { return N; }

instead of:

public static final int N = ...;

Another pitfall arises when static-final is inappropriately used to declare mutable data. (See guideline OBJ01-J. Be aware that a final reference may not always refer to immutable data.) .

Noncompliant Code Example

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*EX1*: According to the Java Language Specification \[[JLS 2005|AA. Java References#JLS 05]\], sectionSection 9.3 "Field (Constant) Declarations": "Every field declaration in the body of an interface is implicitly {{public}}, {{static}}, and {{final}}. It is permitted to redundantly specify any or all of these modifiers for such fields."

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Failing to declare mathematical constants static and final can lead to thread safety issues as well as inconsistent behavior.

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