为什么我的弹力球程序在第 5 次反弹后没有停止？

Question

我在一段时间内嵌套了一个 for 循环来跟踪时间。如果满足某个条件，while 循环会跟踪反弹。只要满足该条件，for 循环就会继续计数。但是一旦满足条件，循环就会停止。但是，无论 while 循环内的条件如何，它都会继续。

/*
     * @Author Lawton C Mizel
     * @Version 1.0, 07 October 2014
     * 
     * A program that simulates a ball bouncing by computing 
     * its height in feet and each "second" as time passes on 
     * a simulated clock.
     * 
*/
public class bouncyballs001 {
    public static void main(String[] args) {

        // create and connect scanner object
        Scanner keyboard = new Scanner(System.in);

        //introduce program
        System.out.println("Welcome to the bouncing ball program!");

        //prompts the user
        System.out.println("Please enter the initial velocity: ");

        double vel = keyboard.nextInt();

        //initial variables

        double height = 0;
        int bounce = 0;
        while (bounce < 5) {
            for (int time = 0; time <= 30; time++) //counter
            {
                if (time >= 0) {
                    height = height + vel;
                    vel = vel - 32.0;
                }

                if (height < 0) {
                    height = height * -0.5;
                    vel = vel * -0.5;
                    System.out.println("BOUNCE!");
                    bounce++;
                }
                System.out.println("time: " + time + " " + "height: " + height);
            }
        }
    }
}

Answer 1

在时间增加 30 倍之前，您不会到达外部 while 循环。您可以将反弹要求添加到 for 循环并删除 while 循环。发生的情况是，在外部 while 循环中检查反弹之前，您可以在 for 循环中反弹 30 次。

    for(int time=0; time <= 30 && bounce < 5; time++) //counter, bails out if bounce > 5
    {
        if(time >= 0)
        {
        height = height + vel;
        vel = vel - 32.0;
        }

        if(height < 0)
        {
            height = height * -0.5;
            vel = vel * -0.5;
            System.out.println("BOUNCE!");
            bounce++;
        }
        System.out.println("time: "+time+" "+"height: "+height);
    }

或者，您可以使用 if 语句和 break。

Answer 2

你在一个永远不会被调用的条件中有bounce++。

if (height < 0)

永远不会是真的，因为高度从 0 开始并上升（即永远不会是负数）。

这意味着反弹永远不会只是 0。