java 文件操作

按行读取和写入

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 JavaFile {
      public static void main(String[] args) {
            try {
            // read file content from file
            StringBuffer sb= new StringBuffer("");
            FileReader reader = new FileReader("c://test.txt");
            BufferedReader br = new BufferedReader(reader);

            String str = null;
            while((str = br.readLine()) != null) {
                  sb.append(str+"/n");
                  System.out.println(str);
            }
            br.close();
            reader.close();
            // write string to file
            FileWriter writer = new FileWriter("c://test2.txt");
            BufferedWriter bw = new BufferedWriter(writer);
            bw.write(sb.toString());
            bw.close();
            writer.close();
      }catch(FileNotFoundException e) {
            e.printStackTrace();
      }catch(IOException e) {
            e.printStackTrace();
      }
   }
}

package com.file.test;

import java.io.FileWriter;

public class FileMain {
 /**
  * @param args
  * @throws Exception 
  */
 public static void main(String[] args) throws Exception{
  // TODO Auto-generated method stub
  FileManager a = new FileManager("a.txt",new char[]{'\n'});
  FileManager b = new FileManager("b.txt",new char[]{'\n'});
  FileWriter c = new FileWriter("c.txt");
  String aWord = null;
  String bWord = null;
  while((aWord = a.nextWord()) != null){
   c.write(aWord+"\n");
   bWord = b.nextWord();
   if(bWord != null)
    c.write(bWord + "\n");
  }
  while((bWord = b.nextWord())!= null){
   c.write(bWord + "\n");
  }
  c.close();
 }

}

package com.file.test;

import java.io.File;
import java.io.FileReader;

public class FileManager {
    String[] words = null;
    int pos = 0;
    public FileManager(String filename,char[] seperators) throws Exception{
        File f = new File(filename);
        FileReader reader = new FileReader(f);
        char[] buf = new char[(int)f.length()];
        int len = reader.read(buf);
        String results = new String(buf,0,len);
        String regex = null;
        if(seperators.length > 1){
            regex = "" + seperators[0] + "|" +seperators[1];
        }else{
            regex = "" + seperators[0];
        }
        words = results.split(regex);
    }
    
    public String nextWord(){
        if(pos == words.length)
            return null;
        return words[pos++];
    }
}

package com.file.test;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FilenameFilter;
import java.io.InputStream;
import java.io.OutputStream;

public class Jad2Java {
    public static void main(String[] args) throws Exception{
        File srcDir = new File("java");
        if(srcDir.exists()&&srcDir.isDirectory()){
            throw new Exception("目录不存在");
        }
        File[] files = srcDir.listFiles(
                new FilenameFilter(){
                    public boolean accept(File dir,String name){
                        return name.endsWith(".java");
                    }
                }
        );
        System.out.println(files.length);
        File destDir = new File("jad");
        if(!destDir.exists()){
            destDir.mkdir();
        }
        for(File f:files){
            FileInputStream fis = new FileInputStream(f);
            String destFilename = f.getName().replaceAll("\\.java$", ".jad");
            FileOutputStream fos = new FileOutputStream(new File(destDir,destFilename));
            copy(fis,fos);
            fis.close();
            fos.close();
        }
    }
    private static void copy(InputStream ips,OutputStream ops) throws Exception{
        int len = 0;
        byte[] buf = new byte[1024];
        while((len = ips.read(buf))!= -1){
            ops.write(buf,0,len);
        }
    }
}