Java中的无限循环问题

Question

当我在这段代码的底部运行 for 循环时，我得到一个无限循环，每次使用 iif 语句中的输出> 每次都会增加并且不会停止。我很确定这是一个小问题，我只是无法指出......

    import java.util.Scanner;

public class HW2johnson_pp1 {

    public static void main(String args[]) {

        Scanner keyboard = new Scanner(System.in);

        System.out.printf("Please enter the species with the higher" + 
                          " population first\n");
        System.out.printf("Enter the name of your first species ");
        String Species1 = keyboard.nextLine();
        System.out.printf("Enter the species' population: ");
        int Pop1 = keyboard.nextInt();
        System.out.printf("Enter the species' growth rate: ");
        int Growth1 = keyboard.nextInt();

        System.out.printf("Enter the name of your second species: ");
        String Species2 = keyboard.nextLine();
        System.out.printf("Enter the species' population: ");
        int Pop2 = keyboard.nextInt();
        System.out.printf("Enter the species' growth rate: ");
        int Growth2 = keyboard.nextInt();

        if (Pop2 > Pop1) {
            System.out.printf("The first population must be higher. \n");
            System.exit(0);
        }


        Species input1 = new Species();
        input1.name = Species1;
        input1.population = Pop1;
        input1.growthRate = Growth1;

        Species input2 = new Species();
        input2.name = Species2;
        input2.population = Pop2;
        input2.growthRate = Growth2;

        if ((input1.predictPopulation(1) - input2.predictPopulation(1)) <= 
            (input1.predictPopulation(2) - input2.predictPopulation(2))){

            System.out.printf(Species2 + " will never out-populate " + 
                              Species1 + "\n");
        }
        else {

            for (int i = 0; input2.predictPopulation(i) <= 
                            input1.predictPopulation(i); i++) {

                if (input2.predictPopulation(i) == input1.predictPopulation(i)) {
                    System.out.printf(" will out-populate \n");
                }
            }
        }
    }
}

---

public int predictPopulation(int years)
        {
            int result = 0;
            double populationAmount = population;
            int count = years;
            while ((count > 0) && (populationAmount > 0))
            {
                populationAmount = (populationAmount +
                              (growthRate / 100) * populationAmount);
                count--;
            }
            if (populationAmount > 0)
                result = (int)populationAmount;

            return result;
        }

Answer 1

这：

        if (Pop2 > Pop1) {
            Species2 = Species1;
            Pop2 = Pop1;
            Growth1 = Growth2;
        }

没有道理。显然，您的目的是“交换”两个总体的值，但相反，您只是使两个总体相同，因此对于任何 years 值，predictPopulation(years ) 对于两个对象来说是相同的。

---

编辑添加：此测试：

        if ((input1.predictPopulation(1) - input2.predictPopulation(1)) < 
            (input1.predictPopulation(2) - input2.predictPopulation(2)))

不是查看物种 2 最终是否会超过物种 1 的有效方法。如果物种 2 具有更高的比例增长率（GrowthRate），那么它最终将超过物种 1，即使在最初几年，它的绝对增长率较低。 （这仅与您的无限循环无关 - Dampsquid 指出，如果您' d 有 <= 而不是 < — 但这是您需要解决的问题。）

Answer 2

你的问题在这里

 for (int i = 0; input2.predictPopulation(i) <= 
                    input1.predictPopulation(i);我++）{

input1 的人口永远不会少于 input2，这与以下情况之一有关：

1. input1 正在获取一个参数值，该值不允许其“人口”少于 input2（检查输入范围以确保这种情况可能会发生，例如确保 input2 的增长率 > input1)

2. 类本身有问题，强制 input1 始终等于或大于 input2。

编辑：既然您已经发布了 PredictPopulation 的代码，它看起来就像是第一。确保输入 2 的增长率始终大于输入 1。