ProgressMonitorInputStream

 Swing类包中有一个很有用的流过滤器，ProgressMonitorInputStream，它可以自动弹出一个对话框，监视已经读取了多少流。

进度监视器流使用InputStream类的available方法来确定流中的总字节数。不过available方法只报告流中可访问的、未中断的字节数。
进度监视器适用于文件以及HTTP URL,因为它们的长度都是事先可知道的，但它不适用于所有的流。

package swing.progress;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.util.Scanner;

import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.ProgressMonitorInputStream;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;

/*2015-7-6*/
public class ProgressMonitorInputStreamTest {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                JFrame frame = new TextFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setVisible(true);
                frame.setLocationRelativeTo(null);
            }
        });
    }

}

class TextFrame extends JFrame {
    private static final long serialVersionUID = 1L;

    private JMenuItem openItem;
    private JMenuItem exitItem;
    private JTextArea textArea;
    private JFileChooser chooser;
    public static final int DEFAULT_WIDTH = 300;
    public static final int DEFAULT_HEIGHT = 200;

    public TextFrame() {
        setTitle("ProgressMonitorInputStreamTest");
        setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

        textArea = new JTextArea();
        add(new JScrollPane(textArea));

        chooser = new JFileChooser();
        chooser.setCurrentDirectory(new File("."));

        JMenuBar menuBar = new JMenuBar();
        setJMenuBar(menuBar);
        JMenu fileMenu = new JMenu("File");
        menuBar.add(fileMenu);
        openItem = new JMenuItem("Open");
        openItem.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                try {
                    openFile();
                } catch (FileNotFoundException e1) {
                    e1.printStackTrace();
                }

            }
        });

        fileMenu.add(openItem);
        exitItem = new JMenuItem("Exit");
        exitItem.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                System.exit(0);
            }
        });
        fileMenu.add(exitItem);

    }

    protected void openFile() throws FileNotFoundException {
        int r = chooser.showOpenDialog(this);
        if (r != JFileChooser.APPROVE_OPTION) {
            return;
        }

        File f = chooser.getSelectedFile();

        FileInputStream fileIn = new FileInputStream(f);
        ProgressMonitorInputStream progressIn = new ProgressMonitorInputStream(this, "Reading " + f.getName(), fileIn);
        final Scanner in = new Scanner(progressIn);
        textArea.setText("");
        SwingWorker<Void, Void> worker = new SwingWorker<Void, Void>() {

            @Override
            protected Void doInBackground() throws Exception {
                while (in.hasNextLine()) {
                    String line = in.nextLine();
                    textArea.append(line);
                    textArea.append("
");
                }
                in.close();
                return null;
            }

        };
        worker.execute();
    }

}