我正在执行一些非常精确的十进制计算,最后我将其转换为减少的分数。小数位数需要精确到96个小数位数。
由于精度非常重要,因此我使用BigDecimal和BigInteger。
BigDecimal的计算总是返回正确的十进制值,但在某些情况下,我无法将此十进制转换为小数的函数
假设我有一个BigDecimal d
d.toString() = 32.222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222223
当我的函数试图将其转换为分数时,输出
Decimal from BigDecimal is:
32.222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222223
// Run the BigDecimal into getFraction
Denominator before reducing:
1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
Numerator before reducing:
32222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222223
// Reduced fraction turns into:
-1/0
// But should output
290/9
这是我的将小数减为小数的功能:
static int[] getFraction(BigDecimal x) {
BigDecimal x1 = x.stripTrailingZeros();
//System.out.println(x.toString() + " stripped from zeroes");
//System.out.println(x1.scale());
// If scale is 0 or under we got a whole number fraction something/1
if(x1.scale() <= 0) {
//System.out.println("Whole number");
int[] rf = { x.intValue(), 1 };
return rf;
}
// If the decimal is
if(x.compareTo(BigDecimal.ZERO) < 0) {
// Add "-" to fraction when printing from main function
// Flip boolean to indicate negative decimal number
negative = true;
// Flip the BigDecimal
x = x.negate();
// Perform same function on flipped
return getFraction(x);
}
// Split BigDecimal into the intval and fractional val as strings
String[] parts = x.toString().split("\\.");
// Get starting numerator and denominator
BigDecimal denominator = BigDecimal.TEN.pow(parts[1].length());
System.out.println("Denominator :" + denominator.toString());
BigDecimal numerator = (new BigDecimal(parts[0]).multiply(denominator)).add(new BigDecimal(parts[1]));
System.out.println("Numerator :" + numerator.toString());
// Now we reduce
return reduceFraction(numerator.intValue(), denominator.intValue());
}
static int[] reduceFraction(int numerator, int denominator) {
// First find gcd
int gcd = BigInteger.valueOf(numerator).gcd(BigInteger.valueOf(denominator)).intValue();
//System.out.println(gcd);
// Then divide numerator and denominator by gcd
int[] reduced = { numerator / gcd, denominator / gcd };
// Return the fraction
return reduced;
}
如果有人弄清楚我是否犯了任何错误,我将不胜感激!
**更新**
已更改的reduceFraction函数:现在返回String []而不是int []
static String[] reduceFraction(BigDecimal numerator, BigDecimal denominator) {
// First find gcd
BigInteger nu = new BigInteger(numerator.toString());
BigInteger de = new BigInteger(denominator.toString());
BigInteger gcd = nu.gcd(de);
// Then divide numerator and denominator by gcd
nu = nu.divide(gcd);
de = de.divide(gcd);
String[] reduced = { nu.toString(), de.toString() };
// Return the fraction
return reduced;
}
getFraction返回:
// Now we reduce, send BigDecimals for numerator and denominator
return reduceFraction(num, den);
而不是
// Now we reduce
return reduceFraction(numerator.intValue(), denominator.intValue());
仍然从函数中得到错误的答案
现在的输出分数是
// Gcd value
gcd = 1
// Fraction is then:
32222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222223/1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
//gcd Value should be:
gcd = 111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
// Whit this gcd the fraction reduces to:
290/9
// Now we reduce
return reduceFraction(numerator.intValue(), denominator.intValue());
嗯,在这种情况下这一定会失败,因为这里的分子或分母都不适合int
。
分子变为-1908874353,并且在它们上调用intValue()
后分母变为0。您必须携带BigIntegers直到计算结束。
[在将它们转换为int
或long
之前,如果必须这样做,可以通过将它们与Integer.MIN_VALUE
,Integer.MAX_VALUE
,Long.MIN_VALUE
进行比较来检查是否可以将它们转换为那些类型,而不会损失精度。和Long.MAX_VALUE
。