Question

我正在尝试编写一个程序，该程序需要一个人口的出生率和死亡率并循环年度人口，直到它达到0或两倍。

我的问题是，它不断地循环无数的难以辨认的数字，我无法解决它。

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currentPopulation循环中的某处更新while的值，否则while (currentPopulation != -1)将始终评估为true（除非-1是原始值价值），你将最终陷入无限循环。

或许你的意思是

if (currentPopulation != -1)

而不是

while (currentPopulation != -1)

Answer 2

while (currentPopulation != -1)

你的状态永远是真的，因此它将无限迭代。因为您没有在任何地方更改while循环内的currentPopulation值。

在内部while循环结束后，您需要在外部while循环中的某处更改currentPopulation的值。

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

    // Change your `currentPopulation` here
}

编码错误导致无限循环

2 个答案: