分支-16. 计算分段函数(输入实数)

import java.text.DecimalFormat;
import java.util.Scanner; 
public class Main 
{
    public static void main(String[] args)
    {
        DecimalFormat df = new DecimalFormat("0.00");
        Scanner input = new Scanner(System.in);
        String num = input.nextLine();/*这个是重点，可满足输入实数（包括整数和小数）*/
        double x = Double.parseDouble(num);
    　　String string = "f("+df.format(x)+")"+" = ";
       if(x >= 0)
           string += df.format(Math.sqrt(x));
       else
           string += df.format(Math.pow((x + 1),2) + 2 * x + 1 / x);
       System.out.print(string);
    }
}