java - Object wont move based on angle given? -

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so i've been trying make object move based on 2 speeds creates using atan(). every test results in same movement of going straight up.

so decided take out , replace inputted angles oddly work the 4 angles 90 180 270 0.

i'm not sure why goes directions here's code:

public void update() {      updatedir();     move(); }  public void updatedir(){     dir = math.atan(spdy/spdx);       dir =20; //i know here used test if change     dir = dir * math.pi / 180.0;     system.out.println("dir: " + dir); }   public void move() {     x +=   (spd*math.cos(dir));     y -=  (spd * math.sin(dir)); }

any reason why goes in 4 directions?

what @nishant shreshth says true. super important use floating points (like float or double) instead of int dir, x , y variable. otherwise decimal part dir value might truncated, pretty of problem when use radians , trigonometric functions.

also note want use math.atan2(spdy, spdx) instead of default atan method use. approach fail spdx gets zero: divide zero. atan2 take care of these edge cases. wikipedia gives details on function.


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