Finding the angle between two bearings is often confusing.[1]



Task

Find the angle which is the result of the subtraction b2 - b1, where b1 and b2 are the bearings.


Input bearings are expressed in the range   -180   to   +180   degrees.

The  result  is also expressed in the range   -180   to   +180   degrees.



Compute the angle for the following pairs:

 20 degrees (b1) and 45 degrees (b2)
 -45 and 45
 -85 and 90
 -95 and 90
 -45 and 125
 -45 and 145
 29.4803 and -88.6381
 -78.3251 and -159.036


Optional extra
 
Allow the input bearings to be any (finite) value.



Test cases

 -70099.74233810938 and 29840.67437876723
 -165313.6666297357 and 33693.9894517456
 1174.8380510598456 and -154146.66490124757
 60175.77306795546 and 42213.07192354373


public class AngleDifference {
 
    public static double getDifference(double b1, double b2) {
        double r = (b2 - b1) % 360.0;
        if (r < -180.0)
            r += 360.0;
        if (r >= 180.0)
            r -= 360.0;
        return r;
    }
 
    public static void main(String[] args) {
        System.out.println("Input in -180 to +180 range");
        System.out.println(getDifference(20.0, 45.0));
        System.out.println(getDifference(-45.0, 45.0));
        System.out.println(getDifference(-85.0, 90.0));
        System.out.println(getDifference(-95.0, 90.0));
        System.out.println(getDifference(-45.0, 125.0));
        System.out.println(getDifference(-45.0, 145.0));
        System.out.println(getDifference(-45.0, 125.0));
        System.out.println(getDifference(-45.0, 145.0));
        System.out.println(getDifference(29.4803, -88.6381));
        System.out.println(getDifference(-78.3251, -159.036));
 
        System.out.println("Input in wider range");
        System.out.println(getDifference(-70099.74233810938, 29840.67437876723));
        System.out.println(getDifference(-165313.6666297357, 33693.9894517456));
        System.out.println(getDifference(1174.8380510598456, -154146.66490124757));
        System.out.println(getDifference(60175.77306795546, 42213.07192354373));
    }
}