继承中的Default constructor cannot handle exception type问题，求大神指点

package it.cast.day21_2930;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.Reader;

public class MyBufferReaderDemo2 extends BufferedReader {
public MyBufferReaderDemo2(Reader in) {
super(in);
// TODO Auto-generated constructor stub
}

public String readLine() throws IOException {
return super.readLine();
}
}


package it.cast.day21_2930;

import java.io.FileReader;

public class MyBufferReaderDemoTest2 {
MyBufferReaderDemo2 mbf2 = new MyBufferReaderDemo2(new FileReader("a.txt"));
[color=#FF0000]//在这里会提示：Default constructor cannot handle exception type FileNotFoundException thrown by implicit super constructor. Must define an explicit constructor 请问怎么解决[/color]

}