file not found exception java?

public void actionPerformed(ActionEvent event) throws exception {

Object source = event.getSource();

if (source == b1)

this is where I tried to put it but error, and it wont let you read file without exception handler

import java.awt.BorderLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.JOptionPane;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JTextArea;

import java.io.*;

import java.util.Scanner;

import java.io.IOException;

public class ViewerFrame extends JFrame {

private JButton b1,b2;

private JTextArea field;

private JPanel panel, panel2;

public ViewerFrame(){

super.setTitle("My Reader");

b1 = new JButton("Open");

b2 = new JButton("Clear");

field = new JTextArea(25,25);

panel = new JPanel();

panel2 = new JPanel();

panel.add(b1);

panel.add(b2);

panel2.add(field,BorderLayout.CENTER);

add(panel, BorderLayout.NORTH);

add(panel2, BorderLayout.CENTER);

b1.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent event) {

Object source = event.getSource();

if (source == b1)

{

String input = JOptionPane.showInputDialog(null, "Enter Input:", "Dialog for Input",

JOptionPane.QUESTION_MESSAGE);

setTitle(input);

FileReader fileR = new FileReader(input);

Scanner scan = new Scanner(fileR);

while (scan.hasNextLine() )

{

field.append(scan.nextLine());

}

}

}

}

);

b2.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent event) {

Object source = event.getSource();

if (source == b2)

setTitle("My Reader");

field.setText( "");

}

}

);

}

}