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POJava: When dividing by factorials, how do I store the factorial? Its too large to be double
 

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  1. POJava: When dividing by factorials, how do I store the factorial? Its too large to be double
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    <p>I am new to java, and my program is likely nowhere near as efficient as it could be, but here it is:</p> <pre><code>public class Compute { public static void main(String[] args) { for(double i = 10000; i &lt;= 100000; i += 10000) { System.out.println("The value for the series when i = " + i + " is " + e(i)); } } public static double e(double input) { double e = 0; for(double i = 0; i &lt;= input; i++) { e += 1 / factorial(input); } return e; } public static double factorial(double input) { double factorial = 1; for(int i = 1; i &lt;= input; i++) { factorial *= i; } return factorial; } } </code></pre> <p>I believe this calculates the value e for i = 10000, 20000, ..., &amp; 100000.<br> Where e = 1 + (1/1!) + (2/2!) + ... + (1/i!)<br> It takes about 47 seconds to do so, but I believe it works.</p> <p>My issue is, for every i, the result is always 0.0<br> I believe this is because whenever the method factorial is called, the return value is too big to be stored which somehow causes a problem. </p> <p>What can I do to store the value returned by the method Factorial?</p>
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    1. USJeff Click
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    1. CO[`100000!` has 456,574 digits](http://www.nitrxgen.net/factorialcalc.php). Without knowing what you're _actually_ trying to accomplish it will be hard for anyone to answer your question in a meaningful way.
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      1. POJava: When dividing by factorials, how do I store the factorial? Its too large to be double
      1. USJim Garrison
    2. COIt is for homework, the book says nearly word for word what I said under the code about calculating e for i given the series e. I hope that makes sense, I am unsure of how to make it more understandable. :/
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      1. USJeff Click
    3. COAs Jim Garrison has pointed out, if you want to calculate e so accurately that going to 100000 terms in the series makes a difference, you'll need to store it in something other than a double. If you really need an answer to 400000 decimal places, you should consider a BigInteger for the factorial, and a BigDecimal for both the reciprocal of the factorial, and for the partial sum.
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      1. POJava: When dividing by factorials, how do I store the factorial? Its too large to be double
      1. USDawood ibn Kareem
 

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