问题描述:

`public class BouncingBalls`

{

public static void main(String[] args)

{

double[] balls = new double [10];

double[] x = new double[1];

double[] y = new double[1];

double[] xspeed = new double[1];

double[] yspeed= new double[1];

for(int i = 0; i < 10; i++)

{

x[i] = 0.5;

y[i] = 0.5;

double r = 0.05;

xspeed[i] = Math.random() / (5 * 24);

yspeed[i] = Math.random() / (5 * 24);

while(true)

{

StdDraw.clear();

StdDraw.circle(x[i],y[i],r);

x[i] = x[i] + xspeed[i];

y[i] = y[i] + yspeed[i];

if (x[i] > 1 || x[i] < 0)

xspeed[i] = xspeed[i] * -1;

if (y[i] > 1 || y[i] < 0)

yspeed[i] = yspeed[i] * -1;

StdDraw.show(1000/ 24);

}

}

}

}

I need to print 10 bouncing balls onto the screen and i can not figure out what i am doing wrong that it wont print all 10.

I do not know how to use any of the import methods or any thing like that. so if someone could please help me that would be great!!!

Your draw loop is inside of your for loop. Generally in animation, your draw loop should be the outermost loop.

```
public class BouncingBalls
{
public static void main(String[] args)
{
int balls = 10;
double[] x = new double[balls];
double[] y = new double[balls];
double[] xspeed = new double[balls];
double[] yspeed= new double[balls];
double r = 0.05;
/* initialize balls */
for(int i = 0; i < balls; i++)
{
x[i] = 0.5;
y[i] = 0.5;
xspeed[i] = Math.random() / (5 * 24);
yspeed[i] = Math.random() / (5 * 24);
}
/* draw loop */
while(true)
{
StdDraw.clear();
for(int i = 0; i < balls; i++)
{
/* Draw and update a ball */
StdDraw.circle(x[i],y[i],r);
x[i] = x[i] + xspeed[i];
y[i] = y[i] + yspeed[i];
if (x[i] > 1 || x[i] < 0)
xspeed[i] = xspeed[i] * -1;
if (y[i] > 1 || y[i] < 0)
yspeed[i] = yspeed[i] * -1;
}
StdDraw.show(1000/ 24);
}
}
}
```

You might start by changing you while(true) loop, which will never terminate.