When Are Enum Values Defined?












8















I'm trying to implement something in a semi-efficient manner. In my program, I have an enumerator representing metrics that are used to pass information around in the program.



I have a class that lets me "compose" these metrics into a single object so I can essentially create a "sentence" to give me complex information without having to do any complex parsing of information. They're essentially bit flags but since I'm using an enum, I can have more than just 64 of them.



The problem is that if I'm instantiating instances of this container class a lot, and I go to create an array like so:



metrics = new boolean[Metrics.values().length];


I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:



private static final int METRIC_COUNT = Metrics.values().length;


Can I do this? Or would the compiler not have defined the enumerated values before it declares this static variable? I know this isn't the best explanation of my question, but I'm not sure how else to word it.



I know the static variable will be determined at runtime (unless the value assigned to it were a literal value), so would the program be able to request the members of the Metrics enum at this point in execution?










share|improve this question


















  • 2





    You can certainly cache the length statically. Though I don't see where the array comes in. If you want to mimic a bit field, consider EnumSet.

    – shmosel
    1 hour ago






  • 2





    stackoverflow.com/a/32354397/2970947

    – Elliott Frisch
    1 hour ago






  • 1





    Further to @ElliotFrisch's link, calling values() does create a copy of the enum's array (as opposed to exposing the Enum's own private one, which would open it to being modified).

    – racraman
    1 hour ago











  • FYI, the enum facility in Java (based on Enum class) is usually just called “enum” or “enum type” to avoid confusion with the interface java.util.Enumeration.

    – Basil Bourque
    1 hour ago


















8















I'm trying to implement something in a semi-efficient manner. In my program, I have an enumerator representing metrics that are used to pass information around in the program.



I have a class that lets me "compose" these metrics into a single object so I can essentially create a "sentence" to give me complex information without having to do any complex parsing of information. They're essentially bit flags but since I'm using an enum, I can have more than just 64 of them.



The problem is that if I'm instantiating instances of this container class a lot, and I go to create an array like so:



metrics = new boolean[Metrics.values().length];


I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:



private static final int METRIC_COUNT = Metrics.values().length;


Can I do this? Or would the compiler not have defined the enumerated values before it declares this static variable? I know this isn't the best explanation of my question, but I'm not sure how else to word it.



I know the static variable will be determined at runtime (unless the value assigned to it were a literal value), so would the program be able to request the members of the Metrics enum at this point in execution?










share|improve this question


















  • 2





    You can certainly cache the length statically. Though I don't see where the array comes in. If you want to mimic a bit field, consider EnumSet.

    – shmosel
    1 hour ago






  • 2





    stackoverflow.com/a/32354397/2970947

    – Elliott Frisch
    1 hour ago






  • 1





    Further to @ElliotFrisch's link, calling values() does create a copy of the enum's array (as opposed to exposing the Enum's own private one, which would open it to being modified).

    – racraman
    1 hour ago











  • FYI, the enum facility in Java (based on Enum class) is usually just called “enum” or “enum type” to avoid confusion with the interface java.util.Enumeration.

    – Basil Bourque
    1 hour ago
















8












8








8








I'm trying to implement something in a semi-efficient manner. In my program, I have an enumerator representing metrics that are used to pass information around in the program.



I have a class that lets me "compose" these metrics into a single object so I can essentially create a "sentence" to give me complex information without having to do any complex parsing of information. They're essentially bit flags but since I'm using an enum, I can have more than just 64 of them.



The problem is that if I'm instantiating instances of this container class a lot, and I go to create an array like so:



metrics = new boolean[Metrics.values().length];


I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:



private static final int METRIC_COUNT = Metrics.values().length;


Can I do this? Or would the compiler not have defined the enumerated values before it declares this static variable? I know this isn't the best explanation of my question, but I'm not sure how else to word it.



I know the static variable will be determined at runtime (unless the value assigned to it were a literal value), so would the program be able to request the members of the Metrics enum at this point in execution?










share|improve this question














I'm trying to implement something in a semi-efficient manner. In my program, I have an enumerator representing metrics that are used to pass information around in the program.



I have a class that lets me "compose" these metrics into a single object so I can essentially create a "sentence" to give me complex information without having to do any complex parsing of information. They're essentially bit flags but since I'm using an enum, I can have more than just 64 of them.



The problem is that if I'm instantiating instances of this container class a lot, and I go to create an array like so:



metrics = new boolean[Metrics.values().length];


I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:



private static final int METRIC_COUNT = Metrics.values().length;


Can I do this? Or would the compiler not have defined the enumerated values before it declares this static variable? I know this isn't the best explanation of my question, but I'm not sure how else to word it.



I know the static variable will be determined at runtime (unless the value assigned to it were a literal value), so would the program be able to request the members of the Metrics enum at this point in execution?







java






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked 1 hour ago









Darin BeaudreauDarin Beaudreau

191116




191116








  • 2





    You can certainly cache the length statically. Though I don't see where the array comes in. If you want to mimic a bit field, consider EnumSet.

    – shmosel
    1 hour ago






  • 2





    stackoverflow.com/a/32354397/2970947

    – Elliott Frisch
    1 hour ago






  • 1





    Further to @ElliotFrisch's link, calling values() does create a copy of the enum's array (as opposed to exposing the Enum's own private one, which would open it to being modified).

    – racraman
    1 hour ago











  • FYI, the enum facility in Java (based on Enum class) is usually just called “enum” or “enum type” to avoid confusion with the interface java.util.Enumeration.

    – Basil Bourque
    1 hour ago
















  • 2





    You can certainly cache the length statically. Though I don't see where the array comes in. If you want to mimic a bit field, consider EnumSet.

    – shmosel
    1 hour ago






  • 2





    stackoverflow.com/a/32354397/2970947

    – Elliott Frisch
    1 hour ago






  • 1





    Further to @ElliotFrisch's link, calling values() does create a copy of the enum's array (as opposed to exposing the Enum's own private one, which would open it to being modified).

    – racraman
    1 hour ago











  • FYI, the enum facility in Java (based on Enum class) is usually just called “enum” or “enum type” to avoid confusion with the interface java.util.Enumeration.

    – Basil Bourque
    1 hour ago










2




2





You can certainly cache the length statically. Though I don't see where the array comes in. If you want to mimic a bit field, consider EnumSet.

– shmosel
1 hour ago





You can certainly cache the length statically. Though I don't see where the array comes in. If you want to mimic a bit field, consider EnumSet.

– shmosel
1 hour ago




2




2





stackoverflow.com/a/32354397/2970947

– Elliott Frisch
1 hour ago





stackoverflow.com/a/32354397/2970947

– Elliott Frisch
1 hour ago




1




1





Further to @ElliotFrisch's link, calling values() does create a copy of the enum's array (as opposed to exposing the Enum's own private one, which would open it to being modified).

– racraman
1 hour ago





Further to @ElliotFrisch's link, calling values() does create a copy of the enum's array (as opposed to exposing the Enum's own private one, which would open it to being modified).

– racraman
1 hour ago













FYI, the enum facility in Java (based on Enum class) is usually just called “enum” or “enum type” to avoid confusion with the interface java.util.Enumeration.

– Basil Bourque
1 hour ago







FYI, the enum facility in Java (based on Enum class) is usually just called “enum” or “enum type” to avoid confusion with the interface java.util.Enumeration.

– Basil Bourque
1 hour ago














3 Answers
3






active

oldest

votes


















4














EnumSet




"compose" these metrics into a single object



essentially bit flags




Sounds like you need a bit-array, with a bit flipped for the presence/absence of each predefined enum value.



If so, no need to roll your own. Use EnumSet or EnumMap. These are special implementations of the Set and Map interfaces. These classes are extremely efficient because of their nature handling enums, taking very little memory and being very fast to execute.



Take for example the built-in DayOfWeek enum. Defines seven objects, one for each day of the week per ISO 8601 calendar.



Set< DayOfWeek > weekend = EnumSet.of( DayOfWeek.SATURDAY , DayOfWeek.SUNDAY ) ;


Use the convenient methods of Set such as contains.



boolean isTodayWeekend = weekend.contains( LocalDate.now().getDayOfWeek() ) ;


If you loop the elements of the set, they are promised to be provided in the order in which they are defined within the enum (their “natural” order). So, logically, an EnumSet should have been marked as a SortedSet, but mysteriously was not so marked. Nevertheless, you know the order. For example, looping EnumSet.allOf( DayOfWeek.class ) renders DayOfWeek.MONDAY first and DayOfWeek.SUNDAY last (per the ISO 8601 standard).




When Are Enum Values Defined?




The elements of an enum are defined at compile-time, and cannot be modified at runtime. Each named variable is populated with an instance when the class is loaded. See Section 8.9, Enum Types of Java Language Specification.



If you define an enum Pet with DOG, CAT, and BIRD, then you know you will have exactly three instances at all times during runtime.



You can count the number of elements defined in an enum in at least two ways:




  • Calling the values method generated by the compiler for any enum, where you can ask the size of the resulting array, as you show in your Question.
    int countDows = DayOfWeek.values().length() ;

  • Calling Set::size after creating an EnumSet of all enum instances.
    int countDows = EnumSet.allOf( DayOfWeek.class ).size() ;






share|improve this answer





















  • 1





    @DarinBeaudreau You will find EnumSet (and EnumMap) quite useful. Notice the methods to copy, invert (complementOf), empty (noneOf & removeAll), and quickly define a subset of a large number of elements (range).

    – Basil Bourque
    45 mins ago



















4















private static final int METRIC_COUNT = Metrics.values().length;


Can I do this?




Yes, you can. This is exactly the right way to cache the length and ensure it's only computed once.




I know the static variable will be determined at runtime (unless the value assigned to it were a literal value), so would the program be able to request the members of the Metrics enum at this point in execution?




Yep. As defined, METRIC_COUNT is also computed at runtime.






share|improve this answer































    -2














    I don't know if you need to do this in this case, but I think I understand the more general problem of not being able to compute a constant early in your execution. I've had this problem. The solution I've used is something like this...compute METRICS_COUNT later on, when you're ready to use it and are sure that the Metrics object is defined, but still only once:



    private static int METRIC_COUNT = -1;

    public static int getMetricsCount() {
    if (METRIC_COUNT < 0)
    METRIC_COUNT = Metrics.values().length;
    return METRIC_COUNT;
    }


    Note that I'm not addressing the Enum problem specifically, as others are in the comments. I'm just proposing a way of putting off setting of a global value until just when it is needed.






    share|improve this answer


























    • Why would this need to be done? It's important to address "Can I do this?" because if the answer is "yes" then there's no need to delay the computation. And if the answer is "no" then it would be good to explain why not.

      – John Kugelman
      1 hour ago













    • This doesn't compile, you can't assign the static final variable METRIC_COUNT in the getMetricsCount() method.

      – Erwin Bolwidt
      1 hour ago











    • The idea is perfectly sound. I just neglected to take the 'static' out of the OPs original definition of METRIC_COUNT. I apologize for not dropping this into a IDE window. Took out the word 'static'. - and @John, I DID answer his question. He said "I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:" - I answered this: a) static context, b) don't have to recalculate.

      – Steve
      1 hour ago













    • private final static int METRIC_COUNT = Metrics.values().length already avoids the recalculation. There's no need to delay the computation.

      – John Kugelman
      1 hour ago













    • All of the in the comments would require a lot of reading and research to even know if it answer's the OP's "can I?" question. I answered "Yes" to his question. How does anything else here provide either a simple "Yes" or "No". You guys are too set on technical perfection rather than solving a guy's problem and getting him moving on to the next one.

      – Steve
      1 hour ago











    Your Answer






    StackExchange.ifUsing("editor", function () {
    StackExchange.using("externalEditor", function () {
    StackExchange.using("snippets", function () {
    StackExchange.snippets.init();
    });
    });
    }, "code-snippets");

    StackExchange.ready(function() {
    var channelOptions = {
    tags: "".split(" "),
    id: "1"
    };
    initTagRenderer("".split(" "), "".split(" "), channelOptions);

    StackExchange.using("externalEditor", function() {
    // Have to fire editor after snippets, if snippets enabled
    if (StackExchange.settings.snippets.snippetsEnabled) {
    StackExchange.using("snippets", function() {
    createEditor();
    });
    }
    else {
    createEditor();
    }
    });

    function createEditor() {
    StackExchange.prepareEditor({
    heartbeatType: 'answer',
    autoActivateHeartbeat: false,
    convertImagesToLinks: true,
    noModals: true,
    showLowRepImageUploadWarning: true,
    reputationToPostImages: 10,
    bindNavPrevention: true,
    postfix: "",
    imageUploader: {
    brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
    contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
    allowUrls: true
    },
    onDemand: true,
    discardSelector: ".discard-answer"
    ,immediatelyShowMarkdownHelp:true
    });


    }
    });














    draft saved

    draft discarded


















    StackExchange.ready(
    function () {
    StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f54877109%2fwhen-are-enum-values-defined%23new-answer', 'question_page');
    }
    );

    Post as a guest















    Required, but never shown

























    3 Answers
    3






    active

    oldest

    votes








    3 Answers
    3






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    4














    EnumSet




    "compose" these metrics into a single object



    essentially bit flags




    Sounds like you need a bit-array, with a bit flipped for the presence/absence of each predefined enum value.



    If so, no need to roll your own. Use EnumSet or EnumMap. These are special implementations of the Set and Map interfaces. These classes are extremely efficient because of their nature handling enums, taking very little memory and being very fast to execute.



    Take for example the built-in DayOfWeek enum. Defines seven objects, one for each day of the week per ISO 8601 calendar.



    Set< DayOfWeek > weekend = EnumSet.of( DayOfWeek.SATURDAY , DayOfWeek.SUNDAY ) ;


    Use the convenient methods of Set such as contains.



    boolean isTodayWeekend = weekend.contains( LocalDate.now().getDayOfWeek() ) ;


    If you loop the elements of the set, they are promised to be provided in the order in which they are defined within the enum (their “natural” order). So, logically, an EnumSet should have been marked as a SortedSet, but mysteriously was not so marked. Nevertheless, you know the order. For example, looping EnumSet.allOf( DayOfWeek.class ) renders DayOfWeek.MONDAY first and DayOfWeek.SUNDAY last (per the ISO 8601 standard).




    When Are Enum Values Defined?




    The elements of an enum are defined at compile-time, and cannot be modified at runtime. Each named variable is populated with an instance when the class is loaded. See Section 8.9, Enum Types of Java Language Specification.



    If you define an enum Pet with DOG, CAT, and BIRD, then you know you will have exactly three instances at all times during runtime.



    You can count the number of elements defined in an enum in at least two ways:




    • Calling the values method generated by the compiler for any enum, where you can ask the size of the resulting array, as you show in your Question.
      int countDows = DayOfWeek.values().length() ;

    • Calling Set::size after creating an EnumSet of all enum instances.
      int countDows = EnumSet.allOf( DayOfWeek.class ).size() ;






    share|improve this answer





















    • 1





      @DarinBeaudreau You will find EnumSet (and EnumMap) quite useful. Notice the methods to copy, invert (complementOf), empty (noneOf & removeAll), and quickly define a subset of a large number of elements (range).

      – Basil Bourque
      45 mins ago
















    4














    EnumSet




    "compose" these metrics into a single object



    essentially bit flags




    Sounds like you need a bit-array, with a bit flipped for the presence/absence of each predefined enum value.



    If so, no need to roll your own. Use EnumSet or EnumMap. These are special implementations of the Set and Map interfaces. These classes are extremely efficient because of their nature handling enums, taking very little memory and being very fast to execute.



    Take for example the built-in DayOfWeek enum. Defines seven objects, one for each day of the week per ISO 8601 calendar.



    Set< DayOfWeek > weekend = EnumSet.of( DayOfWeek.SATURDAY , DayOfWeek.SUNDAY ) ;


    Use the convenient methods of Set such as contains.



    boolean isTodayWeekend = weekend.contains( LocalDate.now().getDayOfWeek() ) ;


    If you loop the elements of the set, they are promised to be provided in the order in which they are defined within the enum (their “natural” order). So, logically, an EnumSet should have been marked as a SortedSet, but mysteriously was not so marked. Nevertheless, you know the order. For example, looping EnumSet.allOf( DayOfWeek.class ) renders DayOfWeek.MONDAY first and DayOfWeek.SUNDAY last (per the ISO 8601 standard).




    When Are Enum Values Defined?




    The elements of an enum are defined at compile-time, and cannot be modified at runtime. Each named variable is populated with an instance when the class is loaded. See Section 8.9, Enum Types of Java Language Specification.



    If you define an enum Pet with DOG, CAT, and BIRD, then you know you will have exactly three instances at all times during runtime.



    You can count the number of elements defined in an enum in at least two ways:




    • Calling the values method generated by the compiler for any enum, where you can ask the size of the resulting array, as you show in your Question.
      int countDows = DayOfWeek.values().length() ;

    • Calling Set::size after creating an EnumSet of all enum instances.
      int countDows = EnumSet.allOf( DayOfWeek.class ).size() ;






    share|improve this answer





















    • 1





      @DarinBeaudreau You will find EnumSet (and EnumMap) quite useful. Notice the methods to copy, invert (complementOf), empty (noneOf & removeAll), and quickly define a subset of a large number of elements (range).

      – Basil Bourque
      45 mins ago














    4












    4








    4







    EnumSet




    "compose" these metrics into a single object



    essentially bit flags




    Sounds like you need a bit-array, with a bit flipped for the presence/absence of each predefined enum value.



    If so, no need to roll your own. Use EnumSet or EnumMap. These are special implementations of the Set and Map interfaces. These classes are extremely efficient because of their nature handling enums, taking very little memory and being very fast to execute.



    Take for example the built-in DayOfWeek enum. Defines seven objects, one for each day of the week per ISO 8601 calendar.



    Set< DayOfWeek > weekend = EnumSet.of( DayOfWeek.SATURDAY , DayOfWeek.SUNDAY ) ;


    Use the convenient methods of Set such as contains.



    boolean isTodayWeekend = weekend.contains( LocalDate.now().getDayOfWeek() ) ;


    If you loop the elements of the set, they are promised to be provided in the order in which they are defined within the enum (their “natural” order). So, logically, an EnumSet should have been marked as a SortedSet, but mysteriously was not so marked. Nevertheless, you know the order. For example, looping EnumSet.allOf( DayOfWeek.class ) renders DayOfWeek.MONDAY first and DayOfWeek.SUNDAY last (per the ISO 8601 standard).




    When Are Enum Values Defined?




    The elements of an enum are defined at compile-time, and cannot be modified at runtime. Each named variable is populated with an instance when the class is loaded. See Section 8.9, Enum Types of Java Language Specification.



    If you define an enum Pet with DOG, CAT, and BIRD, then you know you will have exactly three instances at all times during runtime.



    You can count the number of elements defined in an enum in at least two ways:




    • Calling the values method generated by the compiler for any enum, where you can ask the size of the resulting array, as you show in your Question.
      int countDows = DayOfWeek.values().length() ;

    • Calling Set::size after creating an EnumSet of all enum instances.
      int countDows = EnumSet.allOf( DayOfWeek.class ).size() ;






    share|improve this answer















    EnumSet




    "compose" these metrics into a single object



    essentially bit flags




    Sounds like you need a bit-array, with a bit flipped for the presence/absence of each predefined enum value.



    If so, no need to roll your own. Use EnumSet or EnumMap. These are special implementations of the Set and Map interfaces. These classes are extremely efficient because of their nature handling enums, taking very little memory and being very fast to execute.



    Take for example the built-in DayOfWeek enum. Defines seven objects, one for each day of the week per ISO 8601 calendar.



    Set< DayOfWeek > weekend = EnumSet.of( DayOfWeek.SATURDAY , DayOfWeek.SUNDAY ) ;


    Use the convenient methods of Set such as contains.



    boolean isTodayWeekend = weekend.contains( LocalDate.now().getDayOfWeek() ) ;


    If you loop the elements of the set, they are promised to be provided in the order in which they are defined within the enum (their “natural” order). So, logically, an EnumSet should have been marked as a SortedSet, but mysteriously was not so marked. Nevertheless, you know the order. For example, looping EnumSet.allOf( DayOfWeek.class ) renders DayOfWeek.MONDAY first and DayOfWeek.SUNDAY last (per the ISO 8601 standard).




    When Are Enum Values Defined?




    The elements of an enum are defined at compile-time, and cannot be modified at runtime. Each named variable is populated with an instance when the class is loaded. See Section 8.9, Enum Types of Java Language Specification.



    If you define an enum Pet with DOG, CAT, and BIRD, then you know you will have exactly three instances at all times during runtime.



    You can count the number of elements defined in an enum in at least two ways:




    • Calling the values method generated by the compiler for any enum, where you can ask the size of the resulting array, as you show in your Question.
      int countDows = DayOfWeek.values().length() ;

    • Calling Set::size after creating an EnumSet of all enum instances.
      int countDows = EnumSet.allOf( DayOfWeek.class ).size() ;







    share|improve this answer














    share|improve this answer



    share|improve this answer








    edited 36 mins ago

























    answered 1 hour ago









    Basil BourqueBasil Bourque

    112k28386545




    112k28386545








    • 1





      @DarinBeaudreau You will find EnumSet (and EnumMap) quite useful. Notice the methods to copy, invert (complementOf), empty (noneOf & removeAll), and quickly define a subset of a large number of elements (range).

      – Basil Bourque
      45 mins ago














    • 1





      @DarinBeaudreau You will find EnumSet (and EnumMap) quite useful. Notice the methods to copy, invert (complementOf), empty (noneOf & removeAll), and quickly define a subset of a large number of elements (range).

      – Basil Bourque
      45 mins ago








    1




    1





    @DarinBeaudreau You will find EnumSet (and EnumMap) quite useful. Notice the methods to copy, invert (complementOf), empty (noneOf & removeAll), and quickly define a subset of a large number of elements (range).

    – Basil Bourque
    45 mins ago





    @DarinBeaudreau You will find EnumSet (and EnumMap) quite useful. Notice the methods to copy, invert (complementOf), empty (noneOf & removeAll), and quickly define a subset of a large number of elements (range).

    – Basil Bourque
    45 mins ago













    4















    private static final int METRIC_COUNT = Metrics.values().length;


    Can I do this?




    Yes, you can. This is exactly the right way to cache the length and ensure it's only computed once.




    I know the static variable will be determined at runtime (unless the value assigned to it were a literal value), so would the program be able to request the members of the Metrics enum at this point in execution?




    Yep. As defined, METRIC_COUNT is also computed at runtime.






    share|improve this answer




























      4















      private static final int METRIC_COUNT = Metrics.values().length;


      Can I do this?




      Yes, you can. This is exactly the right way to cache the length and ensure it's only computed once.




      I know the static variable will be determined at runtime (unless the value assigned to it were a literal value), so would the program be able to request the members of the Metrics enum at this point in execution?




      Yep. As defined, METRIC_COUNT is also computed at runtime.






      share|improve this answer


























        4












        4








        4








        private static final int METRIC_COUNT = Metrics.values().length;


        Can I do this?




        Yes, you can. This is exactly the right way to cache the length and ensure it's only computed once.




        I know the static variable will be determined at runtime (unless the value assigned to it were a literal value), so would the program be able to request the members of the Metrics enum at this point in execution?




        Yep. As defined, METRIC_COUNT is also computed at runtime.






        share|improve this answer














        private static final int METRIC_COUNT = Metrics.values().length;


        Can I do this?




        Yes, you can. This is exactly the right way to cache the length and ensure it's only computed once.




        I know the static variable will be determined at runtime (unless the value assigned to it were a literal value), so would the program be able to request the members of the Metrics enum at this point in execution?




        Yep. As defined, METRIC_COUNT is also computed at runtime.







        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered 1 hour ago









        John KugelmanJohn Kugelman

        244k54406457




        244k54406457























            -2














            I don't know if you need to do this in this case, but I think I understand the more general problem of not being able to compute a constant early in your execution. I've had this problem. The solution I've used is something like this...compute METRICS_COUNT later on, when you're ready to use it and are sure that the Metrics object is defined, but still only once:



            private static int METRIC_COUNT = -1;

            public static int getMetricsCount() {
            if (METRIC_COUNT < 0)
            METRIC_COUNT = Metrics.values().length;
            return METRIC_COUNT;
            }


            Note that I'm not addressing the Enum problem specifically, as others are in the comments. I'm just proposing a way of putting off setting of a global value until just when it is needed.






            share|improve this answer


























            • Why would this need to be done? It's important to address "Can I do this?" because if the answer is "yes" then there's no need to delay the computation. And if the answer is "no" then it would be good to explain why not.

              – John Kugelman
              1 hour ago













            • This doesn't compile, you can't assign the static final variable METRIC_COUNT in the getMetricsCount() method.

              – Erwin Bolwidt
              1 hour ago











            • The idea is perfectly sound. I just neglected to take the 'static' out of the OPs original definition of METRIC_COUNT. I apologize for not dropping this into a IDE window. Took out the word 'static'. - and @John, I DID answer his question. He said "I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:" - I answered this: a) static context, b) don't have to recalculate.

              – Steve
              1 hour ago













            • private final static int METRIC_COUNT = Metrics.values().length already avoids the recalculation. There's no need to delay the computation.

              – John Kugelman
              1 hour ago













            • All of the in the comments would require a lot of reading and research to even know if it answer's the OP's "can I?" question. I answered "Yes" to his question. How does anything else here provide either a simple "Yes" or "No". You guys are too set on technical perfection rather than solving a guy's problem and getting him moving on to the next one.

              – Steve
              1 hour ago
















            -2














            I don't know if you need to do this in this case, but I think I understand the more general problem of not being able to compute a constant early in your execution. I've had this problem. The solution I've used is something like this...compute METRICS_COUNT later on, when you're ready to use it and are sure that the Metrics object is defined, but still only once:



            private static int METRIC_COUNT = -1;

            public static int getMetricsCount() {
            if (METRIC_COUNT < 0)
            METRIC_COUNT = Metrics.values().length;
            return METRIC_COUNT;
            }


            Note that I'm not addressing the Enum problem specifically, as others are in the comments. I'm just proposing a way of putting off setting of a global value until just when it is needed.






            share|improve this answer


























            • Why would this need to be done? It's important to address "Can I do this?" because if the answer is "yes" then there's no need to delay the computation. And if the answer is "no" then it would be good to explain why not.

              – John Kugelman
              1 hour ago













            • This doesn't compile, you can't assign the static final variable METRIC_COUNT in the getMetricsCount() method.

              – Erwin Bolwidt
              1 hour ago











            • The idea is perfectly sound. I just neglected to take the 'static' out of the OPs original definition of METRIC_COUNT. I apologize for not dropping this into a IDE window. Took out the word 'static'. - and @John, I DID answer his question. He said "I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:" - I answered this: a) static context, b) don't have to recalculate.

              – Steve
              1 hour ago













            • private final static int METRIC_COUNT = Metrics.values().length already avoids the recalculation. There's no need to delay the computation.

              – John Kugelman
              1 hour ago













            • All of the in the comments would require a lot of reading and research to even know if it answer's the OP's "can I?" question. I answered "Yes" to his question. How does anything else here provide either a simple "Yes" or "No". You guys are too set on technical perfection rather than solving a guy's problem and getting him moving on to the next one.

              – Steve
              1 hour ago














            -2












            -2








            -2







            I don't know if you need to do this in this case, but I think I understand the more general problem of not being able to compute a constant early in your execution. I've had this problem. The solution I've used is something like this...compute METRICS_COUNT later on, when you're ready to use it and are sure that the Metrics object is defined, but still only once:



            private static int METRIC_COUNT = -1;

            public static int getMetricsCount() {
            if (METRIC_COUNT < 0)
            METRIC_COUNT = Metrics.values().length;
            return METRIC_COUNT;
            }


            Note that I'm not addressing the Enum problem specifically, as others are in the comments. I'm just proposing a way of putting off setting of a global value until just when it is needed.






            share|improve this answer















            I don't know if you need to do this in this case, but I think I understand the more general problem of not being able to compute a constant early in your execution. I've had this problem. The solution I've used is something like this...compute METRICS_COUNT later on, when you're ready to use it and are sure that the Metrics object is defined, but still only once:



            private static int METRIC_COUNT = -1;

            public static int getMetricsCount() {
            if (METRIC_COUNT < 0)
            METRIC_COUNT = Metrics.values().length;
            return METRIC_COUNT;
            }


            Note that I'm not addressing the Enum problem specifically, as others are in the comments. I'm just proposing a way of putting off setting of a global value until just when it is needed.







            share|improve this answer














            share|improve this answer



            share|improve this answer








            edited 1 hour ago

























            answered 1 hour ago









            SteveSteve

            771111




            771111













            • Why would this need to be done? It's important to address "Can I do this?" because if the answer is "yes" then there's no need to delay the computation. And if the answer is "no" then it would be good to explain why not.

              – John Kugelman
              1 hour ago













            • This doesn't compile, you can't assign the static final variable METRIC_COUNT in the getMetricsCount() method.

              – Erwin Bolwidt
              1 hour ago











            • The idea is perfectly sound. I just neglected to take the 'static' out of the OPs original definition of METRIC_COUNT. I apologize for not dropping this into a IDE window. Took out the word 'static'. - and @John, I DID answer his question. He said "I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:" - I answered this: a) static context, b) don't have to recalculate.

              – Steve
              1 hour ago













            • private final static int METRIC_COUNT = Metrics.values().length already avoids the recalculation. There's no need to delay the computation.

              – John Kugelman
              1 hour ago













            • All of the in the comments would require a lot of reading and research to even know if it answer's the OP's "can I?" question. I answered "Yes" to his question. How does anything else here provide either a simple "Yes" or "No". You guys are too set on technical perfection rather than solving a guy's problem and getting him moving on to the next one.

              – Steve
              1 hour ago



















            • Why would this need to be done? It's important to address "Can I do this?" because if the answer is "yes" then there's no need to delay the computation. And if the answer is "no" then it would be good to explain why not.

              – John Kugelman
              1 hour ago













            • This doesn't compile, you can't assign the static final variable METRIC_COUNT in the getMetricsCount() method.

              – Erwin Bolwidt
              1 hour ago











            • The idea is perfectly sound. I just neglected to take the 'static' out of the OPs original definition of METRIC_COUNT. I apologize for not dropping this into a IDE window. Took out the word 'static'. - and @John, I DID answer his question. He said "I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:" - I answered this: a) static context, b) don't have to recalculate.

              – Steve
              1 hour ago













            • private final static int METRIC_COUNT = Metrics.values().length already avoids the recalculation. There's no need to delay the computation.

              – John Kugelman
              1 hour ago













            • All of the in the comments would require a lot of reading and research to even know if it answer's the OP's "can I?" question. I answered "Yes" to his question. How does anything else here provide either a simple "Yes" or "No". You guys are too set on technical perfection rather than solving a guy's problem and getting him moving on to the next one.

              – Steve
              1 hour ago

















            Why would this need to be done? It's important to address "Can I do this?" because if the answer is "yes" then there's no need to delay the computation. And if the answer is "no" then it would be good to explain why not.

            – John Kugelman
            1 hour ago







            Why would this need to be done? It's important to address "Can I do this?" because if the answer is "yes" then there's no need to delay the computation. And if the answer is "no" then it would be good to explain why not.

            – John Kugelman
            1 hour ago















            This doesn't compile, you can't assign the static final variable METRIC_COUNT in the getMetricsCount() method.

            – Erwin Bolwidt
            1 hour ago





            This doesn't compile, you can't assign the static final variable METRIC_COUNT in the getMetricsCount() method.

            – Erwin Bolwidt
            1 hour ago













            The idea is perfectly sound. I just neglected to take the 'static' out of the OPs original definition of METRIC_COUNT. I apologize for not dropping this into a IDE window. Took out the word 'static'. - and @John, I DID answer his question. He said "I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:" - I answered this: a) static context, b) don't have to recalculate.

            – Steve
            1 hour ago







            The idea is perfectly sound. I just neglected to take the 'static' out of the OPs original definition of METRIC_COUNT. I apologize for not dropping this into a IDE window. Took out the word 'static'. - and @John, I DID answer his question. He said "I feel like creating an array of the enumerated values so often just to request its size is wasteful. I'm wondering if it's possible to just define the size of the enumerated values() in a static context so it's a constant value I don't have to recalculate:" - I answered this: a) static context, b) don't have to recalculate.

            – Steve
            1 hour ago















            private final static int METRIC_COUNT = Metrics.values().length already avoids the recalculation. There's no need to delay the computation.

            – John Kugelman
            1 hour ago







            private final static int METRIC_COUNT = Metrics.values().length already avoids the recalculation. There's no need to delay the computation.

            – John Kugelman
            1 hour ago















            All of the in the comments would require a lot of reading and research to even know if it answer's the OP's "can I?" question. I answered "Yes" to his question. How does anything else here provide either a simple "Yes" or "No". You guys are too set on technical perfection rather than solving a guy's problem and getting him moving on to the next one.

            – Steve
            1 hour ago





            All of the in the comments would require a lot of reading and research to even know if it answer's the OP's "can I?" question. I answered "Yes" to his question. How does anything else here provide either a simple "Yes" or "No". You guys are too set on technical perfection rather than solving a guy's problem and getting him moving on to the next one.

            – Steve
            1 hour ago


















            draft saved

            draft discarded




















































            Thanks for contributing an answer to Stack Overflow!


            • Please be sure to answer the question. Provide details and share your research!

            But avoid



            • Asking for help, clarification, or responding to other answers.

            • Making statements based on opinion; back them up with references or personal experience.


            To learn more, see our tips on writing great answers.




            draft saved


            draft discarded














            StackExchange.ready(
            function () {
            StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f54877109%2fwhen-are-enum-values-defined%23new-answer', 'question_page');
            }
            );

            Post as a guest















            Required, but never shown





















































            Required, but never shown














            Required, but never shown












            Required, but never shown







            Required, but never shown

































            Required, but never shown














            Required, but never shown












            Required, but never shown







            Required, but never shown







            Popular posts from this blog

            Knooppunt Holsloot

            Altaar (religie)

            Gregoriusmis