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Thread: Array definitions

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    Default Array definitions

    What is the difference between following 2 approaches in creating an array.
    Which is preferred depending on the use?

    Approach 1:


    int a[]= new int[5];
    a[0] = 98;
    a[1] = 97;
    a[2] = 99;
    a[3] = 94;
    a[4] = 96;

    Approach 2:
    int a[]={98,97,99,94,96};

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    Default re: Array definitions

    Also posted and answered at: https://coderanch.com/t/703504/java/array-java
    and https://www.dreamincode.net/forums/t...array-in-java/

    Please use more descriptive title for your posts. All questions on this forum are about Java.
    I've changed this one. Next time be sure to use a better title.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Array definitions

    It doesn't really matter. I prefer the 2nd approach because there is less typing and I'm less likely to make a mistake. But the compiler generates the same byte code for both.

    Regards,
    Jim

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    Default Re: Array definitions

    One issue might be where the code is located. The first would need to be inside a method. The second could be outside of a method.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Array definitions

    Quote Originally Posted by jim829 View Post
    It doesn't really matter. I prefer the 2nd approach because there is less typing and I'm less likely to make a mistake. But the compiler generates the same byte code for both.
    If we're to simply fill the thing with one constant after another, devoid of any other kind of complicated construction, the second approach is dramatically preferable IMO.

    So much about proper coding is in clarity/readability. One of my mantras is to always code for the poor engineer who has to read your code at 3am while hopped up on caffeine....

    In the first case, my own pattern recognition will look several times at the individual assignments and wonder what the reason may be for not using the 2nd well understood idiom. I'd also be forced to verify (painfully if the array were even a little larger) that the indexes were all increasing by 1.

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    Default Re: Array definitions

    The first declaration allocates a variable "a" on the stack which points to the first element of the array on the heap. The heap has 4 spaces allocated for it. You then fill those spaces up with following declarations. This is called dynamic allocation. It's useful when you don't know exactly what's going to be in those allocated memory spaces. The second declaration allocates those variables directly on the stack.

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