用Java更好地近似e [英] Better approximation of e with Java

问题描述

我想将e的值近似为任何所需的精度.做这个的最好方式是什么?我最能得到的是e = 2.7182818284590455.任何对以下代码进行修改的示例都将受到赞赏.

I would like to approximate the value of e to any desired precision. What is the best way to do this? The most I've been able to get is e = 2.7182818284590455. Any examples on a modification of the following code would be appreciated.

public static long fact(int x){
    long prod = 1;
    for(int i = 1; i <= x; i++)
        prod = prod * i;
    return prod;
}//fact

public static void main(String[] args) {
    double e = 1;
    for(int i = 1; i < 50; i++)
        e = e + 1/(double)(fact(i));
    System.out.print("e = " + e);
}//main

推荐答案

使用 BigDecimal ，而不是double.

Use a BigDecimal instead of a double.

BigDecimal e = BigDecimal.ONE;
BigDecimal fact = BigDecimal.ONE;

for(int i=1;i<100;i++) {
  fact = fact.multiply(new BigDecimal(i));

  e = e.add(BigDecimal.ONE.divide(fact, new MathContext(10000, RoundingMode.HALF_UP)));
}

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