问题
I am trying to keep two decimal places, even if then numbers are zeroes, using DecimalFormatter
:
DecimalFormat df = new DecimalFormat("#.00");
m_interest = Double.valueOf(df.format(m_principal * m_interestRate));
m_newBalance = Double.valueOf(df.format(m_principal + m_interest - m_payment));
m_principal = Double.valueOf(df.format(m_newBalance));
However for some values this gives two decimal places, and for others it doesnt. How can i fix this?
回答1:
It is because you are using Double.valueOf
on the DecimalFormat
and it is converting the formatted number back to a double, therefore eliminating the trailing 0s.
To fix this, only use the DecimalFormat
when you are displaying the value.
If you need m_interest
calculations, keep it as a regular double
.
Then when displaying, use:
System.out.print(df.format(m_interest));
Example:
DecimalFormat df = new DecimalFormat("#.00");
double m_interest = 1000;
System.out.print(df.format(m_interest)); // prints 1000.00
回答2:
DecimalFormat and NumberFormat should work just fine. A currency instance could work even better:
import java.text.DecimalFormat;
import java.text.NumberFormat;
public class Foo {
public static void main(String[] args) {
DecimalFormat df = new DecimalFormat("#0.00");
NumberFormat nf = NumberFormat.getInstance();
nf.setMinimumFractionDigits(2);
nf.setMaximumFractionDigits(2);
NumberFormat cf = NumberFormat.getCurrencyInstance();
System.out.printf("0 with df is: %s%n", df.format(0));
System.out.printf("0 with nf is: %s%n", nf.format(0));
System.out.printf("0 with cf is: %s%n", cf.format(0));
System.out.println();
System.out.printf("12345678.3843 with df is: %s%n",
df.format(12345678.3843));
System.out.printf("12345678.3843 with nf is: %s%n",
nf.format(12345678.3843));
System.out.printf("12345678.3843 with cf is: %s%n",
cf.format(12345678.3843));
}
}
This would output:
0 with df is: 0.00
0 with nf is: 0.00
0 with cf is: $0.00
12345678.3843 with df is: 12345678.38
12345678.3843 with nf is: 12,345,678.38
12345678.3843 with cf is: $12,345,678.38
回答3:
Use BigDecimal instead, which supports the formatting approach you seek.
This question details it: How to print formatted BigDecimal values?
回答4:
m_interest = Double.valueOf(String.format("%.2f", sum));
回答5:
Why don't you simply Math.round(value * 100) / 100.0 ?
来源:https://stackoverflow.com/questions/20463196/java-always-keep-two-decimal-places-even-in-zeroes