java - DecimalFormat 未返回正确的数字

问题描述

下面是这个特定任务的提示：让 x 是任何实数。编写一个程序，使用二分法（ https://docs.python.org/3/library/functions.html#format）计算 x 的平方根。请注意，您应该将此问题简化为对 a 和 b 进行自然选择的二分法（即，用户不需要提供 a 和 b）。注意Math.pow和Math.sqrt是不允许的。

问题是当我输入整数如 100（其根为“10.0”但控制台返回“9.999997615814209”）或 36（“6.0”但控制台返回“5.999997138977051”时，我没有得到正确的答案）。我认为这可能与我正在对数字进行四舍五入的事实有关，或者只是因为我doubles一般使用但我不太了解编程中的数学。谢谢你帮助我。

import java.text.DecimalFormat;
import java.util.Scanner;

public class BisectionMethod {

    public double a = 0;
    public double b;
    public double userInput;
    public int iteration = 0;
    public double midpoint;

    public static void main(String[] args) {
        BisectionMethod testClass = new BisectionMethod();
        System.out.println("Answer: " + testClass.FindAnswer(testClass.FindInput(), testClass.a, testClass.FindInterval()));
    }

    public double FindInput() {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter the number to find the root for: ");
        userInput = sc.nextDouble();
        while (userInput < 0) {
            System.out.println("Please enter a number bigger than 0: ");
            userInput = sc.nextDouble();
        }
        sc.close();
        return userInput;
    }

    public double FindInterval() {
        while (b * b < userInput) {
            b = b + 1;
        }
        return b;
    }

    public double RoundNumber(double number) {
        //Rounds number to 4 decimal places.
        String pattern = "#.####";
        DecimalFormat formatNumber = new DecimalFormat(pattern);
        double rounded = Double.valueOf(formatNumber.format(number));
        return rounded;
    }

    public double FindAnswer(double number, double interval1, double interval2) {

        midpoint = (interval1 + interval2) / 2;
        double difference = (midpoint * midpoint) - number;

        while (RoundNumber(difference) != 0) {
            midpoint = (interval1 + interval2) / 2;
            difference = (midpoint * midpoint) - number;
            if (midpoint * midpoint < number) {
                interval1 = midpoint;
            } else {
                interval2 = midpoint;
            }
            iteration = iteration + 1;
        }
        System.out.println("Iterations: " + iteration);
        return midpoint;
    }
}

标签： javadoubledecimalformat

java - DecimalFormat 未返回正确的数字

问题描述

解决方案

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