问题
I want to format this String:
String number = "3.4213946120686956E-9";
to this:
String number = "3.42E-9";
Rounding to 2 decimals. How can I achieve it?
回答1:
Try new DecimalFormat("0.##E0"). Javadoc: DecimalFormat
Example:
public class Test {
private static java.text.DecimalFormat sf = new java.text.DecimalFormat("0.##E0");
public static void main(String[] args) {
System.out.println(sf.format(Double.parseDouble("3.4213946120686956E-9")));
}
};
Output: 3.42E-9
回答2:
This is not the most elegant solution but you could:
EX: String number = "3.4213946120686956E-9";
if the String has a period and an E in it
split the string by the period, and get the first 2 characters after the period = 42
get the last 3 characters at the end = E-9
and then just add it back together with all the characters before the period = 3 + "." + 42 + E-9
回答3:
Read about DecimalFormat.
String number = "3.4213946120686956E-9";
DecimalFormat format = new DecimalFormat("#.##E0");
System.out.println(format.format(new BigDecimal(number)));
来源：https://stackoverflow.com/questions/25692274/java-format-numbers-in-scientific-notation