import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
public class a extends JFrame
{
JTextArea box=new JTextArea(100,100);
public a()
{
super("read");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(600,300);
JScrollPane pane=new JScrollPane(box);
getContentPane().add(pane);
try {
//File f=new File(".txt");
FileReader file = new
FileReader("123.txt");
BufferedReader buff = new
BufferedReader(file);
//boolean eof = false;
StringBuffer buf=new StringBuffer();
/* while (!eof) {
String line = buff.readLine();

if (line == null)
eof = true;
else
buf.append(line+"\n");
}*/
String s=null;
if(buff!=null)
{
while((s=buff.readLine())!=null)
{

if(s.startsWith("**"));
//break;
buf.append("\n"+s);
if(s.startsWith("endend"))
{box.setText(buf.toString());
buff.close();}
}
}

} catch (IOException e) {
System.out.println("Error -- " + e.toString());
}
show();
}
public static void main(String args[])
{
new a();
}
}
这个程序的目的是一次只读出一个题目，但是实现不了？各位高手给个意见，谢谢！

1.Which interface does java.util.Hashable implement?
A. java.util.Map
B. java.util.List
C. java.util.Hashable
D. java.util.Collection
** Given:
（1）. public class X {
（2）. public object m () {
（3）. object o = new Float (3.14F);
（4）. object [] oa = new object [1];
（5）. oa[0]= o;
（6）. o = null;
（7）. oa[0] = null;
（8）.return o;
（9）. }
（10）. }
2.When is the float object created in line 3, eligible for garbage collection?
A. Just after line 5
B. Just after line 6
C. Just after line 7
D. Just after line 8(that is, as the method returns)
就好像这样的题目，一次只能读出一个

不同的题目有不同的实现方法吗？