Java - Math.floor() method example

The Math.floor() function returns an integer value that is smaller than or equal to the argument - the result of round down operation.  

public class MathExample {

    public static void main(String[] args) {
        System.out.println( Math.floor(  5     ) ); //  5.0

        System.out.println( Math.floor(  2.49  ) ); //  2.0
        System.out.println( Math.floor(  2.50  ) ); //  2.0
        System.out.println( Math.floor(  2.51  ) ); //  2.0

        System.out.println( Math.floor( -2.49  ) ); // -3.0
        System.out.println( Math.floor( -2.50  ) ); // -3.0
        System.out.println( Math.floor( -2.51  ) ); // -3.0

        System.out.println( Math.floor(  0.999 ) ); //  0.0
        System.out.println( Math.floor(  1.001 ) ); //  1.0
        System.out.println( Math.floor( -1.001 ) ); // -2.0
    }
}

1. Documentation

package java.lang;

public final class Math {

    public static double floor(double number) { ... }

}

2. Rounding with precision down-to n places example

public class MathExample {
    
    static double floorPrecised(double number, int precision) {
        double power = Math.pow(10, precision);

        return Math.floor(number * power) / power;
    }

    public static void main(String[] args) {
        System.out.println( floorPrecised(     5  ,  0 ) ); // 5.0
        System.out.println( floorPrecised(     5. ,  0 ) ); // 5.0
        System.out.println( floorPrecised(      .5,  0 ) ); // 0.0

        System.out.println( floorPrecised(  1.1234,  0 ) ); // 1.0
        System.out.println( floorPrecised(  1.1234,  1 ) ); // 1.1
        System.out.println( floorPrecised(  1.1235,  2 ) ); // 1.12
        System.out.println( floorPrecised(  1.1235,  3 ) ); // 1.123

        System.out.println( floorPrecised( -1.1234,  0 ) ); // -2.0
        System.out.println( floorPrecised( -1.1234,  1 ) ); // -1.2
        System.out.println( floorPrecised( -1.1234,  2 ) ); // -1.13
        System.out.println( floorPrecised( -1.1234,  3 ) ); // -1.124

        System.out.println( floorPrecised(    1234, -1 ) ); // 1230.0
        System.out.println( floorPrecised(    1234, -2 ) ); // 1200.0
        System.out.println( floorPrecised(    1234, -3 ) ); // 1000.0

        System.out.println( floorPrecised(  5_000.000_001,  0 ) ); // 5000.0
        System.out.println( floorPrecised(  5_000.000_001,  6 ) ); // 5000.000001
        System.out.println( floorPrecised(  5_000.000_001, -3 ) ); // 5000.0
    }
}

References

1. Floor and ceiling functions - Wikipedia