初级弧度/度转换程序

Question

在Java方面，我是个初学者，我创建了这个小代码来帮助我掌握一些小的主题。它允许它的用户将一个激进度量转换为一个度度量，将一个度度量转换为一个激进度量。这是我的最后代码：

import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader;
import java.util.ArrayList; 

public class MainClass {

    public static void dtr (BufferedReader dRead) throws IOException {

        ArrayList<Integer> divisors = new ArrayList<Integer>();
        ArrayList<Integer> gcd = new ArrayList<Integer>();


        int d = Integer.parseInt(dRead.readLine());
        for (int pd = 1; pd <= d; pd++) {
            if (d % pd == 0) {
                divisors.add(pd);               
            }
        }

        for (int index = 0; index < divisors.size(); ++index) {
            if (180.0 % divisors.get(index) == 0) {
                gcd.add(divisors.get(index));
            }

        }

        int dem = (180 / gcd.get(gcd.size() - 1));
        if ((d / (gcd.get(gcd.size() - 1))) == 1) {
            System.out.print("Radical: pi / " + dem);
        } else {
            System.out.print("Radical: " + (d / (gcd.get(gcd.size() - 1))) + "pi / " + dem);
        }

    }

    public static void rtd (BufferedReader rnRead, BufferedReader rdRead) throws IOException {

        int rn = Integer.parseInt(rnRead.readLine());
        int rd = Integer.parseInt(rdRead.readLine());

        int dividend = rn * 180;

        System.out.print("Degrees: " + (dividend / rd));

    }

    public static void main(String[] args) throws IOException {

        System.out.println("Do you want to convert from radicals to degrees, or degrees to radicals?");
        System.out.print("Use \"R\" for radials to degrees, and \"D\" for degrees to radicals: ");
        BufferedReader userInput = new BufferedReader(new InputStreamReader(System.in));
        String userChoice = userInput.readLine();

        if (userChoice.contains("D") || userChoice.contains("d")) {

            System.out.print("Degrees: ");
            BufferedReader dRead = new BufferedReader(new InputStreamReader(System.in));
            dtr(dRead);

        } else if (userChoice.contains("R") || userChoice.contains("r")) {

            System.out.println("Radical numerator (omit pi): ");
            BufferedReader rnRead = new BufferedReader(new InputStreamReader(System.in));
            System.out.println("Radical denominator: ");
            BufferedReader rdRead = new BufferedReader(new InputStreamReader(System.in));
            rtd(rnRead, rdRead);

        } else {

            System.out.println("Invalid response. Please restart the program.");

        }

    }

}

我知道这段代码有多糟糕，但我只想知道是否有任何方法可以优化这些代码的功能，因为我想将这些概念应用到将来的所有工作中。

Answer 1

现在，通常忽略赋值右侧的泛型类型，而不是

 ArrayList<Integer> divisors = new ArrayList<Integer>(); 

你可以写

 ArrayList<Integer> divisors = new ArrayList<>(); 

由于您没有使用任何ArrayList特定的功能，所以将divisors声明为List (gcd也是如此)是比较干净的。

 List<Integer> divisors = new ArrayList<>();

调用gcd.get(gcd.size() )需要一个具有合理名称的单独方法。

对于BufferedReader userInput ...，虽然在本例中不关闭IO资源是无害的，但通常这样做是很好的做法。查看“尝试使用资源语句”：https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html。

同样常见的做法是重用Reader，而不是每次需要执行读取操作时都创建一个新的阅读器。考虑到这一点，您将得到如下内容：

public static void main(String[] args) throws IOException {
    System.out.println("Do you want to convert from radicals to degrees, or degrees to radicals?");
    System.out.print("Use \"R\" for radials to degrees, and \"D\" for degrees to radicals: ");
    try (BufferedReader userInput = new BufferedReader(new InputStreamReader(System.in))) {
        String userChoice = userInput.readLine();

        if (userChoice.contains("D") || userChoice.contains("d")) {

            System.out.print("Degrees: ");
            dtr(userInput);

        } else if (userChoice.contains("R") || userChoice.contains("r")) {

            System.out.println("Radical numerator (omit pi): ");
            System.out.println("Radical denominator: ");
            rtd(userInput);

        } else {

            System.out.println("Invalid response. Please restart the program.");
        }
    }
}

注意，现在rtd只需要一个参数。因为您在读取用户输入之前进行打印，所以用户可以看到

 Radical numerator (omit pi): 
 Radical denominator: 

在她有机会提供任何意见之前。这些语句应该移动到与读取用户输入交织的rtd中。

 if (userChoice.contains("D") || userChoice.contains("d"))

可以简化如下：

if (userChoice.toLowerCase().contains("d")) {     

Answer 2

欧氏算法是计算两个整数最大公因子的一种著名而有效的方法.

与您的方法相比，欧几里德算法速度更快，代码更少，并且不需要额外的存储。

例如，使用

// https://rosettacode.org/wiki/Greatest_common_divisor#Iterative_Euclid.27s_Algorithm
public static int gcd(int a, int b) {
    while (b > 0) {
        int c = a % b;
        a = b;
        b = c;
    }
    return a;
}

将分数简化为

int degrees = Integer.parseInt(dRead.readLine());
int commonDivisor = gcd(degrees, 180);
int numerator = degrees / commonDivisor;
int denominator = 180 / commonDivisor;