huffmanframe.java

利用霍夫曼树实现文本压缩。如果是文本可以压缩到40％的大小

package org.galaxy_OPEN.www.datastructures.huffman;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.JFileChooser;
import javax.swing.filechooser.FileFilter;
import java.io.*;
import java.util.*;

public class HuffmanFrame extends JFrame implements ActionListener {
	private FilterFileChooser fileChooser = null;

	private JTextField filePathField = new JTextField(60);

	private JButton jbOpen = new JButton("打开");

	private JButton jbCompress = new JButton("压缩");

	private JButton jbDecompress = new JButton("解压");

	private JTextArea message = new JTextArea();

	private File file = null;

	// construct the frame
	public HuffmanFrame() {
		setTitle("文本压缩 - Galaxy-OPEN");
		setSize(450, 350);
		setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

		Container content = getContentPane();

		filePathField.setEditable(false);
		filePathField.setBackground(Color.WHITE);
		filePathField.setForeground(Color.BLACK);
		jbOpen.addActionListener(this);
		JPanel northPane = new JPanel();
		northPane.setLayout(new FlowLayout());
		northPane.add(filePathField);
		northPane.add(jbOpen);
		content.add(northPane, BorderLayout.NORTH);

		JScrollPane scrollPane = new JScrollPane(message);
		setMessage("文件压缩程序，请选择文件导入。");
		message.setEditable(false);
		message.setWrapStyleWord(true);
		content.add(scrollPane, BorderLayout.CENTER);

		jbCompress.addActionListener(this);
		jbDecompress.addActionListener(this);
		JPanel southPane = new JPanel();
		southPane.setLayout(new FlowLayout());
		southPane.add(jbCompress);
		southPane.add(jbDecompress);
		content.add(southPane, BorderLayout.SOUTH);

		// center the window
		Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
		Dimension frameSize = getSize();
		if (frameSize.height > screenSize.height) {
			frameSize.height = screenSize.height;
		}
		if (frameSize.width > screenSize.width) {
			frameSize.width = screenSize.width;
		}
		setLocation((screenSize.width - frameSize.width) / 2,
				(screenSize.height - frameSize.height) / 2);

		// set look and feel
		try {
			UIManager
					.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
			SwingUtilities.updateComponentTreeUI(this);
		} catch (Exception e) {
			JOptionPane.showMessageDialog(null, "错误！",
					"系统错误，即将退出。请与制作人员联系/[e-mail]",
					JOptionPane.ERROR);
			// e.printStackTrace();
		}

		setResizable(false);
	}

	public void setMessage(String text) {
		String date = (new Date()).toString();
		date = date.substring(11, 19) + "-->";
		message.insert(date + text + "\n", 0);
	}

	public boolean isOutputFileExists(String outPath) {
		File outputFile = new File(outPath);
		return outputFile.exists() ? true : false;
	}

	public String getOperate() {
		String operate = null;
		if (file != null) {
			String name = file.getName();
			int length = name.length();

			if ((name.endsWith(".huf") || name.endsWith(".HUF"))
					&& name.charAt(length - 4) == '.') {
				operate = "decompress";
			} else {
				operate = "compress";
			}
		}
		return operate;
	}

	private void openFile(String op) {
		fileChooser = new FilterFileChooser(op);
		int choice = fileChooser.showOpenDialog(this);
		if (choice == JFileChooser.APPROVE_OPTION) {
			file = fileChooser.getSelectedFile();
			if (file == null) {
				return;
			}
			String filePath = file.getPath();
			setMessage("已选择文件：" + filePath);
			filePathField.setText(filePath);
		}
	}

	private void compressFile() {
		if (file == null) {
			openFile("compress");
		}
		String operate = getOperate();
		if (operate == null) {
			return;
		} else if (operate.equals("compress")) {
			jbCompress.setEnabled(false);
			String inPath = file.getPath();
			String outPath = getPath("compress");
			if (isOutputFileExists(outPath)) {
				JOptionPane.showMessageDialog(this, "文件已经存在！", "警告",
						JOptionPane.WARNING_MESSAGE);
				setMessage(outPath + " 文件已经存在！");
				jbCompress.setEnabled(true);
				filePathField.setText("");
				file = null;
				return;
			}
			setMessage("准备压缩，请稍候……");

			// compress
			try {
				Compress com = new Compress(this, inPath, outPath);
				com.encode();
			} catch (IOException exc) {
				JOptionPane.showMessageDialog(this, "压缩文件\n" + outPath
						+ "\n过程发生错误！", "I/O错误", JOptionPane.ERROR_MESSAGE);
			}
			jbCompress.setEnabled(true);
			filePathField.setText("");
			file = null;
		}
	}

	private void decompressFile() {
		if (file == null) {
			openFile("decompress");
		}
		String operate = getOperate();
		if (operate == null) {
			return;
		} else if (operate.equals("decompress")) {
			jbDecompress.setEnabled(false);
			String inPath = file.getPath();
			String outPath = getPath("decompress");

			if (isOutputFileExists(outPath)) {
				JOptionPane.showMessageDialog(this, "文件已经存在！", "警告",
						JOptionPane.WARNING_MESSAGE);
				setMessage(outPath + " 文件已经存在！");
				jbCompress.setEnabled(true);
				filePathField.setText("");
				file = null;
				return;
			}
			setMessage("准备解压缩，请稍候……");

			// decompress
			try {
				Decompress dec = new Decompress(this, inPath, outPath);
				dec.decode();
			} catch (IOException exc) {
				exc.printStackTrace();
				JOptionPane.showMessageDialog(this, "解压缩文件\n" + outPath
						+ "\n过程发生错误！", "I/O错误", JOptionPane.ERROR_MESSAGE);
			} catch (ClassNotFoundException exc) {
				JOptionPane.showMessageDialog(this, "解压缩文件\n" + outPath
						+ "\n过程发生错误！文件已被损坏！", "错误", JOptionPane.ERROR_MESSAGE);
			}

			jbDecompress.setEnabled(true);
			filePathField.setText("");
			file = null;
		} else if (operate.equals("compress")) {
			JOptionPane.showMessageDialog(null, "该文件尚未压缩，请选择“压缩”！", "错误！",
					JOptionPane.ERROR_MESSAGE);
		}
	}

	private String getPath(String op) {
		String fileExt = null;
		if (op.equals("compress")) {
			fileExt = ".huf";
		} else if (op.equals("decompress")) {
			fileExt = "";
		}
		String filePath = null;
		if (file != null) {
			String fileName = file.getName();
			filePath = file.getPath();
			int extIndex = fileName.indexOf('.');
			int nameIndex = filePath.indexOf(fileName);
			fileName = fileName.substring(0, extIndex) + fileExt;
			filePath = filePath.substring(0, nameIndex) + fileName;
		}
		return filePath;
	}

	public void actionPerformed(ActionEvent e) {
		JButton jb = (JButton) e.getSource();
		if (jb == jbOpen) {
			openFile("all");
		} else if (jb == jbCompress) {
			compressFile();
		} else if (jb == jbDecompress) {
			decompressFile();
		}
	}

	public static void main(String[] args) {
		try {
			HuffmanFrame mf = new HuffmanFrame();
			mf.setVisible(true);
		} catch (Exception e) {
			JOptionPane.showMessageDialog(null,
					"系统内部错误，程序即将退出！请与制作人员联系/[e-mail]", "系统错误",
					JOptionPane.ERROR_MESSAGE);
		}
	}

	public File getFile() {
		return file;
	}
}

// custom file chooser, only choose picture files
class FilterFileChooser extends JFileChooser {
	private FileFilter[] fileFilter = new FileFilter[] { new HuffmanFileFilter(
			"待解压文件(*.huf)", new String[] { ".huf", ".HUF" }) };

	public FilterFileChooser(final String op) {
		if (op.equals("decompress")) {
			addChoosableFileFilter(fileFilter[0]);
		}
		setMultiSelectionEnabled(false);
	}

	// file filter
	private class HuffmanFileFilter extends javax.swing.filechooser.FileFilter {
		protected String desc;

		protected String[] extensions;

		public HuffmanFileFilter(final String desc, final String[] extensions) {
			this.desc = desc;
			this.extensions = (String[]) extensions.clone();
		}

		public boolean accept(final File f) {
			if (f.isDirectory() == true) {
				return true;
			}

			final String name = f.getName();
			final int length = name.length();

			for (int i = 0; i < extensions.length; i++) {
				final String ext = extensions[i];

				if (name.endsWith(ext)
						&& name.charAt(length - ext.length()) == '.') {
					return true;
				}
			}
			return false;
		}

		public String getDescription() {
			return desc;
		}
	}
}