java学习【文件IO】

博客:http://blog.csdn.net/muyang_ren

1.快速读取一个文本文件，将文件的内容输出到一个新文件；

package lhy.java_day3.oop;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class Test_BuffeRead {

    private static BufferedReader bfReader;
    private static BufferedWriter bfWriter;
    private static String str;

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub

        try {
            bfReader = new BufferedReader(new FileReader("f:/java_day3.txt"));
            bfWriter = new BufferedWriter(new FileWriter("f:/write.txt"));
            while ((str=bfReader.readLine() )!= null) {
                System.out.println(str);
                bfWriter.write(str+"\r\n");
                bfWriter.flush();
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

2.列出某一目录下的后缀为”.java”的文件列表

package lhy.java_day3.oop;

import java.io.File;



public class Test_File {

    private static File fs;

    /**
     * @param args
     */
    public static void main(String[] args) {
        String pathname = "e:\\test";
        try {
            fs = new File(pathname);
            String[] str=fs.list();
            for (String string : str) {
                if(string.endsWith(".java"))
                    System.out.println(string);
            }   
        } catch (NullPointerException e) {
            // TODO: handle exception
            System.out.println("打开目录失败!");
        }   
    }
}

3.复制图片文件

package lhy.java_day3.oop;


import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;


public class Test_picture {

    private static FileInputStream fis;
    private static FileOutputStream fos;
    private static int ret;
    private static byte[] b = new byte[2048]; 
    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub      
        try {
            fis = new FileInputStream("f:\\tu1.jpg");
            fos = new FileOutputStream("f:\\tu2.jpg");

            while (true) {
                ret = fis.read(b, 0, b.length);
                if(ret!=-1){
                    fos.write(b, 0, ret);
                }else {
                    break;
                }           
            }
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}