04747_Java语言程序设计（一）_第9章_输入和输出流

例9.1一个文件复制应用程序，将某个文件的内容全部复制到另一个文件。

import java.io.*;

public class Example9_1 {
	public static void main(String arg[]) {
		File inputFile = new File("file1.txt");
		File outputFile = new File("file2.txt");
		int ch;
		try {
			FileReader in = new FileReader(inputFile);
			FileWriter out = new FileWriter(outputFile);
			System.out.print("文件复制程序开始工作：");
			while ((ch = in.read()) != -1) {
				out.write(ch);
			}
			in.close();
			out.close();
			System.out.print("文件复制程序工作结束：");
		} catch (FileNotFoundException e1) {
			System.out.print("文件没有找到！" + e1);
		} catch (IOException e2) {
			System.out.print("File read Error:" + e2);
		}
	}
}

例9.2说明BufferedReader类的用法的应用程序。

import java.io.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

class MyWindow extends JFrame implements ActionListener {
	JTextArea text;
	BufferedReader in;
	JButton button;
	FileReader file;

	MyWindow() {
		super("缓冲式流的读取");
		Container con = this.getContentPane();// 获得内容面板
		con.setSize(100, 400);
		con.setLayout(new BorderLayout());
		button.addActionListener(this);
		text = new JTextArea(20, 30);
		text.setBackground(Color.cyan);
		JScrollPane jsp = new JScrollPane(text);
		con.add(jsp, BorderLayout.CENTER);
		con.add(button, "South");
		this.setVisible(true);
		this.pack();
		try {
			File f = new File("Example9_3.java");// 指定文件
			file = new FileReader(f);// 创建FileReader对象
			in = new BufferedReader(file);// 接到BufferedReader类对象上
		} catch (FileNotFoundException e1) {
			text.setText("文件没有找到");
			button.removeActionListener(this);
		}
	}

	public void actionPerformed(ActionEvent e) {
		String s;
		if (e.getSource() == button) {
			try {
				while ((s = in.readLine()) != null)// 按行输入
				{
					text.append(s + '\n');// 从文件读出的内容在文本区中输出
				}
			} catch (IOException exp) {
			}
		}
	}
}

public class Example9_2 {
	public static void main(String args[]) {
		MyWindow myWin = new MyWindow();
	}
}

例9.3说明BufferedWriter类用法的应用程序。

import java.util.*;
import java.io.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

class MyWindow extends JFrame implements ActionListener {
	JTextArea text;
	JButton button;
	FileWriter writefile;
	BufferedWriter out;

	MyWindow() {
		super("缓冲式样流的输出");
		Container con = this.getContentPane();// 获得内容面板
		text = new JTextArea(20, 30);
		text.setBackground(Color.cyan);
		button = new JButton("写文件");
		button.addActionListener(this);
		con.setLayout(new BorderLayout());
		con.setSize(40, 40);
		con.setVisible(true);
		con.add(text, "Center");
		con.add(button, "South");
		try {
			writefile = new FileWriter("line.txt");
			out = new BufferedWriter(writefile);
		} catch (IOException e) {
		}
	}

	public void actionPerformed(ActionEvent e) {
		String s;
		if (e.getSource() == button) {// 将文本区内容采用缓冲式输出到文件
			try {
				out.write(text.getText(), 0, (text.getText()).length());
				out.flush();
				text.setText(null);
				System.exit(0);
			} catch (IOException exp) {
				text.setText("文件写出错！\n");
				System.exit(-1);
			}
		}
	}
}

public class Example9_3 {
	public static void main(String args[]) {
		MyWindow myWin = new MyWindow();
		myWin.pack();
	}
}

例9.4一个文件随机读写的应用程序。

import java.io.*;

public class Example9_4 {
	public static void main(String args[]) {
		RandomAccessFile inOut = null;
		long data[] = { 151, 278, 235, 206, -170, 32, 43, 21, 83, 47 };
		try {
			inOut = new RandomAccessFile("longData.dat", "rw");
			for (int i = 0; i < data.length; i++) {
				inOut.writeLong(data[i]);
			}
			for (int i = data.length - 1; i >= 0; i--) {
				inOut.seek(i * 8);// long型数据占8个字节，第i个整数自i*8字节开始
				System.out.print(" " + inOut.readLong() + ((i == 0) ? "\n" : ","));
			}
			inOut.close();
		} catch (FileNotFoundException e1) {
			System.out.println("文件找不到！" + e1);
		} catch (IOException e2) {
			System.out.println("文件读写错！" + e2);
		}
	}
}

例9.5应用程序逐行读取自己的源代码显示。

import java.io.*;

public class Example9_5 {
	public static void main(String args[]) {
		try {
			RandomAccessFile file = new RandomAccessFile("Example9_5.java", "rw");
			long fileCurPos = 0;
			long fileLength = file.length();
			while (fileCurPos < fileLength) {
				String s = file.readLine();
				System.out.println(s);
				fileCurPos = file.getFilePointer();
			}
			file.close();
		} catch (FileNotFoundException e1) {
			System.out.println("文件找不到！" + e1);
		} catch (IOException e2) {
			System.out.println("文件读写错！" + e2);
		}
	}
}

例9.6应用程序利用文件对话框确定数据文件。

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

public class Example9_6 {
	public static void main(String args[]) {
		FrameFileDialog f = new FrameFileDialog();
	}
}

class FrameFileDialog extends JFrame implements ActionListener {
	JFileChooser filedialog = null;
	JLabel label = new JLabel("", JLabel.CENTER);
	JButton b1, b2;
	JTextArea text;

	FrameFileDialog() {
		super("带文件对话框的窗口");
		Container con = this.getContentPane();
		con.setLayout(new BorderLayout());
		con.setSize(40, 50);
		JPanel p = new JPanel();
		b1 = new JButton("打开文件");
		b2 = new JButton("保存文件");
		b1.addActionListener(this);
		b2.addActionListener(this);
		p.add(b1);
		p.add(b2);
		text = new JTextArea(20, 30);
		JScrollPane jsp = new JScrollPane(text);
		filedialog = new JFileChooser("D:\\workspace");
		/* 建立一个JFileChooser对象，并指定目录为默认文件对话框路径 */
		filedialog.setControlButtonsAreShown(true);// 显示打开和撤销按钮
		filedialog.addChoosableFileFilter(new MyFileFilter("txt"));
		filedialog.addChoosableFileFilter(new MyFileFilter("java"));
		text.setBackground(Color.cyan);
		con.add(jsp, BorderLayout.CENTER);
		con.add(label, BorderLayout.NORTH);
		con.add(p, BorderLayout.SOUTH);
		this.setVisible(true);
		this.pack();
	}

	public void actionPerformed(ActionEvent e) {
		File file = null;
		int result;
		if (e.getSource() == b1)// 打开文件
		{
			filedialog.setDialogTitle("打开文件");
			result = filedialog.showOpenDialog(this);
			text.setText("");
			if (result == JFileChooser.APPROVE_OPTION) {
				file = filedialog.getSelectedFile();
				label.setText("你选择打开的文件名称是：" + file.getName());
			} else if (result == JFileChooser.CANCEL_OPTION) {
				label.setText("你没有选择任何文件");
			}
			FileInputStream fileStream = null;
			if (file != null) {
				try {
					fileStream = new FileInputStream(file);
				} catch (FileNotFoundException nfe) {
					label.setText("文件没有找到");
					return;
				}
				int readByte;
				try {
					while ((readByte = fileStream.read()) != -1) {
						text.append(String.valueOf((char) readByte));
					}
					fileStream.close();
				} catch (IOException ie) {
					label.setText("读取文件出错");
				}
			}
		} else if (e.getSource() == b2)// 保存文件
		{
			filedialog.setDialogTitle("保存文件");
			result = filedialog.showSaveDialog(this);
			file = null;
			String fileName;
			if (result == JFileChooser.APPROVE_OPTION) {
				file = filedialog.getSelectedFile();
				label.setText("你选择保存的文件名称是：" + file.getName());
			} else if (result == JFileChooser.CANCEL_OPTION) {
				label.setText("你没有选择任何文件");
			}
			FileOutputStream fileStream = null;
			if (file != null) {
				try {
					fileStream = new FileOutputStream(file);
				} catch (FileNotFoundException nfe) {
					label.setText("文件没有找到");
					return;
				}
				String content = text.getText();
				try {
					fileStream.write(content.getBytes());
					fileStream.close();
				} catch (IOException ie) {
					label.setText("写文件出错");
				}
			}
		}
	}
}

class MyFileFilter extends FileFilter {
	String ext;

	MyFileFilter(String t) {
		ext = t;
	}

	public boolean accept(File file) {
		if (file.isDirectory()) {
			return true;
		}
		String fn = file.getName();
		int index = fn.lastIndexOf(',');
		if (index > 0 && index < fn.length() - 1) {
			String extension = fn.substring(index + 1).toLowerCase();
			if (extension.equals(ext)) {
				return true;
			}
		}
		return false;
	}

	public String getDescription() {
		if (ext.equals("java")) {
			return "JAVA Source File(*.java)";
		}
		if (ext.equals("txt")) {
			return "TXT File(*.txt)";
		}
		return "";
	}
}