W3School TIY Editor

public class Main { public static void main(String[] args) { System.out.println(Math.acos(0.64)); System.out.println(Math.acos(-0.4)); System.out.println(Math.acos(0)); System.out.println(Math.acos(1)); System.out.println(Math.acos(-1)); System.out.println(Math.acos(2)); } }