java - 编码错误导致死循环

Question

我正在尝试编写一个程序，它获取人口的出生率和死亡率，并循环计算年人口，直到它达到 0 或翻倍。

我的问题是它不断循环无穷无尽的难以辨认的数字，我无法修复它。

import java.util.Scanner;
public class Hwk6 {
    public static void main (String[] args) {
        int currentYear, currentPopulation;
        double birthRate, deathRate;
        Scanner stdin = new Scanner(System.in);

        System.out.println("\nPopulation Estimator\n");
        System.out.println("Enter Year");
        currentYear = stdin.nextInt();
        System.out.println("Enter Current Population");
        currentPopulation = stdin.nextInt();
        System.out.println("Enter Birthrate of Population");
        birthRate = stdin.nextDouble();
        System.out.println("Enter Deathrate of Population");
        deathRate = stdin.nextDouble();

        int counter = currentPopulation;
        System.out.println("Population: ");
        while (currentPopulation != -1)
            while (counter < currentPopulation * 2) {
                System.out.print(counter + " ");
                counter = counter + (int)(counter * birthRate - counter * deathRate);
            }
        System.exit(0);
    }
}

Answer 1

在 while 循环的某处更新 currentPopulation 的值，否则 while (currentPopulation != -1) 将总是 计算结果为真(除非 -1 是原始值)，您将陷入无限循环。

或者你的意思是

if (currentPopulation != -1)

代替

while (currentPopulation != -1)