package controller;
/**
 * Created by zhz on 2016/7/18.
 */
public class MainMath {
    public static void main(String[] args) {
        MainMath m  = new MainMath();
System.out.println( m.root(2,0.000000000000001));
}

    /**
     *
     * @param x  要開方的數
     * @param error  允許的誤差範圍
     * @return
*/
public double root
 
(final double x, final double error) {
        double  c = x ;
        double defineStart =  0 ;
        double defineEnd = x ;
        while(defineEnd - defineStart > error){
            double defineMid = (defineStart + defineEnd) / 2.0 ;
            double resultStart =  defineStart*defineStart - c ;
 
            double resultEnd = defineEnd * defineEnd - c ;
            double resultMid = defineMid * defineMid - c ;
            if(resultStart == 0 ){
                return defineStart;
}
            if(resultMid == 0 ){
                return defineMid;
}
            if(resultEnd == 0 ){
                return 
 
defineEnd ;
}
            System.out.println(defineStart + " --- " + defineEnd );
            if( resultStart * resultMid < 0){
                defineEnd = defineMid ;
                continue;
}
            if(resultMid * resultEnd < 0){
                defineStart = defineMid ;
                continue ;
}
        }
        return  defineEnd;
}
}