填空题

本题的功能是用流式布局管理器来管理窗口中的按钮。在执行程序时指定生成按钮的个数，并把这些按钮都放置在流式布局管理器的窗口中。
import java. awt. * ;
import java. awt. event. * ;
import javax. swing. * ;
public class java2

public static void main(String[] args)

if(args. length!=1)

System. out. println("请指定按钮的个数")
System. exit(0);

String buttonString=args[0];
int buttonNumber=______;
ButtonFrame frame=new ButtonFrame(buttonNumber);
frame. setDefaultCloseOperation(JFrame. EXIT_ON_CLOSE);
frame. show();


class ButtonFrame extends JFrame

public ButtonFrame(______)

buttons=buttonNumber;
setTitle("java2");
setSize(WIDTH, HEIGHT);
JPanel buttonPanel=new JPanel();
for(int i=0; i＜buttons; i++)

JButton addButton=new JButton("add"+i);
buttonPanel. add(addButton);

Container contentPane=getContentPane();
contentPane. add(buttonPanel);
public static final int WIDTH=350;
public static final int HEIGHT=200;
private int buttons;