二分法求常数E，常数π，根号2

进行单元测试数据

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public class Test {

    public static void main(String[] args) {

        // TODO Auto-generated method stub

        System.out.println(bin(-1000000000,9999,0.00000001));

    }

    //提供的接口

    //区间[a,b] 和 区间精度d

    static double  bin(double a,double b,double d){

        while(true){

            double mid = (a+b)/2;   //第一步

            if(f3(a)*f3(mid)<0)     //若 ：第二步

                b=mid;

            else

                a=mid;

            if(f3(mid)==0 || b-a<=d)//若 ：第三步

                return (a+b)/2;

        }

    }

    static boolean judge(double a,double b){

        if(a*b<0)

            return true;

        else

            return false;

    }

    static double f1(double x){  // y=x^2 -2 输入x得到函数值y

        return x*x - 2;

    }

    static double f2(double x){ // y=sinx

        return Math.sin(x);

    }

    static double f3(double x){ // y=x-e

        return x-Math.E;

    }

}