Removing trailing zeros from BigDecimal in Java

I need to remove trailing zeros from BigDecimal along with RoundingMode.HALF_UP. For instance,

Value        Output

15.3456  <=> 15.35
15.999   <=> 16            //No trailing zeros.
15.99    <=> 15.99
15.0051  <=> 15.01
15.0001  <=> 15           //No trailing zeros.
15.000000<=> 15           //No trailing zeros.
15.00    <=> 15           //No trailing zeros.

stripTrailingZeros() works but it returns scientific notations in situations like,

new BigDecimal("600.0").setScale(2, RoundingMode.HALF_UP).stripTrailingZeros();

In this case, it returns 6E+2. I need this in a custom converter in JSF where it might be ugly for end users. So, what is the proper way of doing this?

Solution 1:

Use toPlainString()

BigDecimal d = new BigDecimal("600.0").setScale(2, RoundingMode.HALF_UP).stripTrailingZeros();
System.out.println(d.toPlainString()); // Printed 600 for me

I'm not into JSF (yet), but converter might look like this:

@FacesConverter("bigDecimalPlainDisplay")
public class BigDecimalDisplayConverter implements Converter {
    @Override
    public Object getAsObject(FacesContext context, UIComponent component, String value) {
        throw new BigDecimal(value);
    }

    @Override
    public String getAsString(FacesContext context, UIComponent component, Object value) {
        BigDecimal  bd = (BigDecimal)value;
        return bd.setScale(2, RoundingMode.HALF_UP).stripTrailingZeros().toPlainString();
    }
}

and then in xhtml:

<h:inputText id="bigDecimalView" value="#{bigDecimalObject}" 
    size="20" required="true" label="Value">
    <f:converter converterId="bigDecimalPlainDisplay" />
</h:inputText>

Solution 2:

Note that stripTrailingZeros() doesn't do very well either.

On this:

val = new BigDecimal("0.0000").stripTrailingZeros();
System.out.println(val + ": plain=" + val.toPlainString());

val = new BigDecimal("40.0000").stripTrailingZeros();
System.out.println(val + ": plain=" + val.toPlainString());

val = new BigDecimal("40.50000").stripTrailingZeros();
System.out.println(val + ": plain=" + val.toPlainString());

Output (Java 7):

0.0000: plain=0.0000
4E+1: plain=40
40.5: plain=40.5

Output (Java 8):

0: plain=0
4E+1: plain=40
40.5: plain=40.5

The 0.0000 issue in Java 7 is fixed in Java 8 by the following java fix.

Solution 3:

If you want to do this at your BigDecimal object and not convert it into a String with a formatter you can do it on Java 8 with 2 steps:

1. stripTrailingZeros()
2. if scale < 0 setScale to 0 if don't like esponential/scientific notation

You can try this snippet to better understand the behaviour

BigDecimal bigDecimal = BigDecimal.valueOf(Double.parseDouble("50"));
bigDecimal = bigDecimal.setScale(2);
bigDecimal = bigDecimal.stripTrailingZeros();
if (bigDecimal.scale()<0)
    bigDecimal= bigDecimal.setScale(0);
System.out.println(bigDecimal);//50
bigDecimal = BigDecimal.valueOf(Double.parseDouble("50.20"));
bigDecimal = bigDecimal.setScale(2);
bigDecimal = bigDecimal.stripTrailingZeros();
if (bigDecimal.scale()<0)
    bigDecimal= bigDecimal.setScale(0);
System.out.println(bigDecimal);//50.2
bigDecimal = BigDecimal.valueOf(Double.parseDouble("50"));
bigDecimal = bigDecimal.setScale(2);
bigDecimal = bigDecimal.stripTrailingZeros();
System.out.println(bigDecimal);//5E+1
bigDecimal = BigDecimal.valueOf(Double.parseDouble("50.20"));
bigDecimal = bigDecimal.setScale(2);
bigDecimal = bigDecimal.stripTrailingZeros();
System.out.println(bigDecimal);//50.2