Java acm入门
Java acm入门
提问于 2017-08-04 01:11:24
这里才刚刚开始。我以前上过编程课程，但我是Java新手，没有丰富的经验。这个节目来自梅赫兰·萨哈米在斯坦福大学的演讲，并上传到Youtube上。https://www.youtube.com/watch?v=YpZCKVG4s5k&t=1996s从大约32分钟开始，代码是可见的。这是一个简单的图形程序，显示了一个弹跳球。对我来说，这是一个开始尝试设置的好地方，用一个对象替换另一个对象，并总体上习惯于语法如何与屏幕上显示的内容相关。但是，我甚至不能到达比喻的起跑门！我尝试剪切并粘贴到Sololearn仿真器中，但得到了相同的错误。我认为这一定与acm库有关，但是。。。什么？
下面是代码，下面是错误消息。
import acm.program.*;
import acm.graphics.*;
public class BouncingBall extends GraphicsProgram {
private static final int DIAM_BALL = 30;
private static final double GRAVITY = 3;
private static final int DELAY = 50;
private static final double X_START = DIAM_BALL / 2;
private static final double Y_START = 100;
//x velocity
private static final double X_VEL = 5;
//Y velocity determined by gravity and bounce
private static final double BOUNCE_REDUCE = 0.9;
//Starting coords
private double xVel = X_VEL;
private double yVel = 0.0;
//private instance variable
private GOval ball;
}
public void run(){
setup(){
while (ball.getX() < getWidth()) {
moveBall();
checkForCollision();
pause(DELAY);
}
}
//create and place ball
private void setup(){
ball=new GOval(X_START,Y_START,DIAM_BALL,DIAM_BALL);
ball.setFilled(true);
add(ball);
}
//update and move ball
private void moveBall(){
yVel+=GRAVITY;
ball.move(xVel,yVel);
}
//Collision detection
private void checkForCollision(){
if(ball.getY()>getHeight()-DIAM_BALL){
yVel=-yVel*BOUNCE_REDUCE;
double diff=ball.getY()-(getHeight()-DIAM_BALL);
ball.move(0,-2*diff);
}
}
}
}"Error: Java: class，interface，or enum expected“大约有12个，指定(22,12)，(26,17)，(27,17)，(28,13)，(33,13)，(34,13)。。。
我有一种感觉，当我明白为什么其中一些是一个问题时，我将能够解决所有这些问题。
提前感谢！
回答 1
Stack Overflow用户
发布于 2017-08-04 02:44:24
我在文件末尾删除了setup(){和a}，我认为这是问题的原因。
import acm.program.*;
import acm.graphics.*;
public class BouncingBall extends GraphicsProgram {
private static final int DIAM_BALL = 30;
private static final double GRAVITY = 3;
private static final int DELAY = 50;
private static final double X_START = DIAM_BALL / 2;
private static final double Y_START = 100;
//x velocity
private static final double X_VEL = 5;
//Y velocity determined by gravity and bounce
private static final double BOUNCE_REDUCE = 0.9;
//Starting coords
private double xVel = X_VEL;
private double yVel = 0.0;
//private instance variable
private GOval ball;
public void run(){
setup();
while (ball.getX() < getWidth()) {
moveBall();
checkForCollision();
pause(DELAY);
}
}
//create and place ball
private void setup(){
ball=new GOval(X_START,Y_START,DIAM_BALL,DIAM_BALL);
ball.setFilled(true);
add(ball);
}
//update and move ball
private void moveBall(){
yVel+=GRAVITY;
ball.move(xVel,yVel);
}
//Collision detection
private void checkForCollision(){
if(ball.getY()>getHeight()-DIAM_BALL){
yVel=-yVel*BOUNCE_REDUCE;
double diff=ball.getY()-(getHeight()-DIAM_BALL);
ball.move(0,-2*diff);
}
}
}查看35:03的视频，它准确地显示了上面的内容。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/45490655
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