保留N位小数

通过DecimalFormat类实现

import java.util.Scanner;
import java.text.DecimalFormat;

public class Main 
{
	public static void main(String[] args) 
	{
		double value;
		
		Scanner cin = new Scanner(System.in);
		
		value = cin.nextDouble();
		
		// 保留两位小数
		DecimalFormat df = new DecimalFormat("#.00");
		String result = df.format(value);
		
		System.out.println(result);
	}
}

format

public StringBuffer format(double number,
                           StringBuffer result,
                           FieldPosition fieldPosition)

Formats a double to produce a string.

Specified by:

format in class NumberFormat

Parameters:

number - The double to format

result - where the text is to be appended

fieldPosition - On input: an alignment field, if desired. On output: the offsets of the alignment field.

Returns:

The formatted number string

Throws:

ArithmeticException - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY

See Also:

FieldPosition