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POWhy are they holding this many instances(33) even before being asked for? Where did they get the number 16 from?
 

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  1. POWhy are they holding this many instances(33) even before being asked for? Where did they get the number 16 from?
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    <p>When I was studying about static blocks , I wanted to see its usage in java source code . so I referred java.math.BigInteger.java . The static block there was like this </p> <pre><code>/** * Initialize static constant array when class is loaded. */ private final static int MAX_CONSTANT = 16; private static BigInteger posConst[] = new BigInteger[MAX_CONSTANT+1]; private static BigInteger negConst[] = new BigInteger[MAX_CONSTANT+1]; static { for (int i = 1; i &lt;= MAX_CONSTANT; i++) { int[] magnitude = new int[1]; magnitude[0] = i; posConst[i] = new BigInteger(magnitude, 1); negConst[i] = new BigInteger(magnitude, -1); } } </code></pre> <p><a href="https://upsource.jetbrains.com/lib/view/jdk7u10/java/math/BigInteger.java;nav:36548:36556%3afocused" rel="nofollow">static block code in code browser </a></p> <p>From this I am getting a sense that they are creating 33 BigInteger instances and holding it in posConst and negConst . Then later when people call valueOf in <a href="https://upsource.jetbrains.com/lib/view/jdk7u10/java/math/BigInteger.java;nav:35145:35152%3afocused" rel="nofollow">BigInteger.java:valueOf</a></p> <p>if value is between -16 to 16 they take from posConst and negConst and give . If it is beyond this range they create new instance .</p> <p>I can understand that they are holding instances to give it readily if user asks one among that list . On what basis or probability are they holding 33 instances . Is it not a waste of memory . Why not create when user asks and only that particular instance . </p> <p>I cannot understand the trade off attained in this logic . Please help . Am I going wrong in understanding this code . If so please help .</p>
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    1. USHarish Kayarohanam
    1. USHarish Kayarohanam
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    1. CORelated: http://stackoverflow.com/questions/7674391/why-to-avoid-biginteger-instantiation-in-java/7674462#7674462 (but still does not answer the question)
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