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Returns the ordinal of the enumeration constant (its position in its enum declaration, where the initial constant is assigned an ordinal of zero). Most programmers will have no use for this method. It is designed for use by sophisticated enum-based data structures, such as EnumSet and EnumMap.

Noncompliant Code Example

This noncompliant code example declares enum Hydrocarbon and uses its ordinal() method to provide the result of the getNumberOfCarbons() method.

enum Hydrocarbon {
  METHANE, ETHANE, PROPANE, BUTANE, PENTANE,
  HEXANE, HEPTANE, OCTANE, NONANE, DECANE;

  public int getNumberOfCarbons() {
    return ordinal() + 1;
  }
}

Although this noncompliant code example works, its maintenance is susceptible to vulnerabilities. If the enum constants were reordered, the getNumberOfCarbon() method would return incorrect values. Also, BENZENE — which also has 6 carbons — cannot be added without violating the current enum design.

Compliant Solution

In this compliant solution, enum constants are explicitly associated with the corresponding integer values for the number of carbon atoms they contain.

enum Hydrocarbon {
  METHANE(1), ETHANE(2), PROPANE(3), BUTANE(4), PENTANE(5),
  HEXANE(6), HEPTANE(7), OCTANE(8), NONANE(9), DECANE(10);

  private final int numberOfCarbons;

  Hydrocarbon(int carbons) { this.numberOfCarbons = carbons; }

  public int getNumberOfCarbons() {
    return numberOfCarbons;
  }
}

Risk Assessment

Use of ordinals to derive integer values reduces the program's maintainability and can lead to errors in the program.

Related Guidelines

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The CERT C Secure Coding Standard

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INT09-C. Ensure enumeration constants map to unique values

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The CERT C++ Secure Coding Standard

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ISO/IEC TR 24772:2010

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: "Enumerator Issues [

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CCB]"

Bibliography

DCL54-J. Enable compile-time type checking of varargs types      01. Declarations and Initialization (DCL)      DCL02-J. Declare all enhanced for statement loop variables final