写一个Java版的保留精度

import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        double a = in.nextDouble();
        double b = in.nextDouble();
        double c = in.nextDouble();
        java.text.DecimalFormat df = new java.text.DecimalFormat("#.0");
        if(a+b > c && a+c > b && b+c>a){
            System.out.println("Perimetro = " + df.format(a+b+c));
        }else{
            System.out.println("Area = "+ df.format((a+b)*c/2.0));
        }
    }


}