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;
    }

}