Java :: comparing ronded doubles doesn't work

I want to compare two numbers:

• -3.123
• -3.123456

I will use double to store them and I just want to consider the first 3 decimals, so:

import java.math.RoundingMode;
import java.text.DecimalFormat;

public class DecimalComparator {
    public static void main(String[] args) {
        areEqualByThreeDecimalPlaces(-3.123, -3.123456);
    }

    public static boolean areEqualByThreeDecimalPlaces (double one, double two) {
        boolean same = true;

        DecimalFormat df = new DecimalFormat("#.###");
        df.setRoundingMode(RoundingMode.FLOOR);
        System.out.println(df.format(one));
        System.out.println(df.format(two));

        if (df.format(one).equals(df.format(two))) {
            same = true;
            System.out.println("true");
        } else {
            same = false;
            System.out.println("false");
        }
        return same;
    }
}

The code is returning me:

-3.123
-3.124
false

why the second number is rounding to -3.124?

Hi its just that when u round off 3.123456 it works the below way when decimal 
places are reduced :
 
 3.12346
 3.1235
 3.124
 3.12
 3.1 
 
//commenting the set rounding mode will make it work the way u want.
public static void main (String[] args ) {
        double one =-3.123;
         double two = -3.123456;
        boolean same = true;

        DecimalFormat df = new DecimalFormat("#.###");
        //remove this line
        //df.setRoundingMode(RoundingMode.FLOOR);
       
        System.out.println(df.format(one));
        System.out.println(df.format(two));

        if (df.format(one).equals(df.format(two))) {
            same = true;
            System.out.println("true");
        } else {
            same = false;
            System.out.println("false");
        }
        System.out.println(same);
    }

RoundingMode.FLOOR rounds the number towards the lower side - your code would work for positive numbers, but not for negative numbers. You need to use RoundingMode.DOWN that just removes digits after N places:

df.setRoundingMode(RoundingMode.DOWN);
// Here ------------------------^