Java, extract just the fractional part of a BigDecimal?

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

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();

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

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

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

bd = bd.stripTrailingZeros();

before the previous code.