java - 如何在不中断的情况下停止while循环

Question

谁能帮帮我。

子弹从大炮中发射出来，一直飞到落地。如果击中目标(红色)则打印“目标已被击中”，如果没有“击中目标”。

Battle area

但主要问题是我无法停止循环，如果我错过了目标，我就无法使用break;根本没有，只有 while、if、else 或 else if。

No hit和 Hit the target

public static void main(String[] args) {
  Scanner sc=new Scanner(System.in);
  double g=8.86,a=40,delta_t=0.05; // a=angle
  double v0,x,y,t,x0,y0;
  boolean hitTarget = false;

  System.out.println("191RDB107 Vladislavs Fedotovs");
  System.out.println("While operators,07,Urans");

  System.out.print("v0=");
  if (sc.hasNextDouble()) {
    v0 = sc.nextDouble();
  } else {
    System.out.println("input-output error");
    sc.close();
    return;
  }

  sc.close();
  System.out.println("result:");
  System.out.println("t \t x \t y");
  t = 0.1;
  while(hitTarget!=true) {
    
    x =v0*t*Math.cos(Math.toRadians(a));
    y =v0*t*Math.sin(Math.toRadians(a))-(g*Math.pow(t, 2))/2;
    System.out.printf("%3.2f\t%7.3f\t%7.3f\n", t, x, y); // red target
    if ((x >= 12  && x <= 17) && (y <=-2 && y >=-4)) {
      hitTarget=true;
      System.out.print("the target was destroyed");
      t+=0.1;
    } else if (x<=10 && y<=0 || x>=10 && x<=12 && y>=-4 || x>17 && y>=-4) { // green "grass"
      System.out.print("shot off the target");
      t+=0.1;
    } else {
      System.out.print("shot is in the air");
    }

    t+=0.1;
}

Formula which I'm using

Should be something like that.

**基本上，在子弹击中地面(y)后，它应该停止循环。谢谢!!

Answer 1

不要使用“hitTarget”作为 while 循环条件。将其更改为一个单独的变量，让您知道子弹是否在飞行中。当子弹击中目标时，您可以将“hitTarget”设置为 true 以供稍后使用。如果子弹击中目标或者击中草地，可以将bulletInFlight设置为false来退出循环。

boolean bulletInFlight = true;
boolean hitTarget = false;
while (bulletInFlight) {
    x =v0*t*Math.cos(Math.toRadians(a));                    
    y =v0*t*Math.sin(Math.toRadians(a))-(g*Math.pow(t, 2))/2;
    System.out.printf("%3.2f\t%7.3f\t%7.3f\n", t, x, y); // red target
    if ((x >= 12  && x <= 17) && (y <=-2 && y >=-4)) {
        bulletInFlight = false;
        hitTarget = true;
        System.out.print("the target was destroyed");
        t+=0.1;
    } else if (x<=10 && y<=0 || x>=10 && x<=12 && y>=-4 || x>17 && y>=-4) {
        bulletInFlight = false;
        System.out.print("shot off the target");
        t+=0.1;
    } else {
        System.out.print("shot is in the air");
        t+=0.1;
    } 
}
// Now do whatever you need to do once you know the target has been hit or not hit.