Java, extract just the fractional part of a BigDecimal?

问题

In Java, I'm working with the BigDecimal class and part of my code requires me to extract the fractional part from it. BigDecimal does not appear to have any built in methods to help me get the number after the decimal point of a BigDecimal.

For example:

BigDecimal bd = new BigDecimal("23452.4523434");

I want to extract the 4523434 from the number represented above. What's the best way to do it?

回答1:

I would try bd.remainder(BigDecimal.ONE).

Uses the remainder method and the ONE constant.

BigDecimal bd = new BigDecimal( "23452.4523434" );
BigDecimal fractionalPart = bd.remainder( BigDecimal.ONE ); // Result:  0.4523434

回答2:

If the value is negative, using bd.subtract() will return a wrong decimal.

Use this:

BigInteger decimal = 
                bd.remainder(BigDecimal.ONE).movePointRight(bd.scale()).abs().toBigInteger();

It returns 4523434 for 23452.4523434 or -23452.4523434

In addition, if you don't want extra zeros on the right of the fractional part, use:

bd = bd.stripTrailingZeros();

before the previous code.

回答3:

Here's an alternative to using the remainder() method:

BigDecimal bd = new BigDecimal("23452.4523434");
BigDecimal fracBd = bd.subtract(new BigDecimal(bd.toBigInteger()));

Further, you can try the abs() method to ensure the fraction part is positive:

BigDecimal fracBd = bd.subtract(new BigDecimal(bd.toBigInteger())).abs();

回答4:

This return "4523434" , even if you set the number in negative "-23452.4523434".

 BigDecimal d = BigDecimal.valueOf(23452.4523434);
 BigInteger decimal = d.remainder(BigDecimal.ONE).movePointRight(d.scale()).abs().toBigInteger();

回答5:

It doesn't work!!!

BigDecimal d = BigDecimal.valueOf(23452.4523434);
BigInteger decimal = 
d.remainder(BigDecimal.ONE).movePointRight(d.scale()).abs().toBigInteger();

When you input number, which fractional-part starts with '0', for ex. "123.00456". You get "456" instead of "00456". It happens because we convert it .toBigInteger(), and the first zeros just gone; If you use .toString() instead of .toBigInteger(), you get 456.00000, it's wrong too!

So my advise is using this:

BigDecimal fractPart = bd.remainder(BigDecimal.ONE);
StringBuilder sb = new StringBuilder(fractPart.toString());
sb.delete(0, 2);
String str = sb.toString();

And then just use this str how you want

来源：https://stackoverflow.com/questions/10038749/java-extract-just-the-fractional-part-of-a-bigdecimal

标签

java

bigdecimal