Java - 即使在零中也始终保留两位小数
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/20463196/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Java - always keep two decimal places even in zeroes
提问by user3044874
I am trying to keep two decimal places, even if then numbers are zeroes, using DecimalFormatter:
我试图保留两位小数，即使数字为零，使用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?
然而，对于某些值，这给出了两个小数位，而对于其他值，则没有。我怎样才能解决这个问题？
采纳答案by Michael Yaworski
It is because you are using Double.valueOfon the DecimalFormatand it is converting the formatted number back to a double, therefore eliminating the trailing 0s.
这是因为你正在使用Double.valueOf的DecimalFormat，它是转换格式的数字回到了一倍，因此消除了拖尾0。
To fix this, only use the DecimalFormatwhen you are displayingthe value.
为了解决这个问题，只使用DecimalFormat，当你显示的值。
If you need m_interestcalculations, keep it as a regular double.
如果您需要m_interest计算，请将其保留为常规double.
Then when displaying, use:
然后在显示时使用：
System.out.print(df.format(m_interest));
Example:
例子：
DecimalFormat df = new DecimalFormat("#.00");
double m_interest = 1000;
System.out.print(df.format(m_interest)); // prints 1000.00
回答by Rob
Use BigDecimal instead, which supports the formatting approach you seek.
请改用 BigDecimal，它支持您寻求的格式化方法。
This question details it: How to print formatted BigDecimal values?
这个问题详细说明：如何打印格式化的 BigDecimal 值？
回答by Hovercraft Full Of Eels
DecimalFormat andNumberFormat should work just fine. A currency instance could work even better:
DecimalFormat和NumberFormat 应该可以正常工作。货币实例可以更好地工作：
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:
这将输出：
0 with df is: 0.00
0 with nf is: 0.00
0 with cf is: m_interest = Double.valueOf(String.format("%.2f", sum));
.00
12345678.3843 with df is: 12345678.38
12345678.3843 with nf is: 12,345,678.38
12345678.3843 with cf is: ,345,678.38
回答by pinxue
Why don't you simply Math.round(value * 100) / 100.0 ?
你为什么不简单地 Math.round(value * 100) / 100.0 ？
