Java实现文件的读写，复制

 import java.io.BufferedInputStream;
 import java.io.BufferedOutputStream;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.InputStream;
 import java.io.OutputStream;

 /**
  * 测试文件的读取、写入、复制功能
  * @package :java05
  * @author shaobn
  * @Describe :测试文件的读取、写入、复制功能
  * @Time: 2015-9-5 下午10:50:18
  */
 public class TestCopyText {
     public static void main(String[] args) throws Exception{
         //读取文件并打印
         System.out.println(readText(new FileInputStream("D:\\hello.txt")));
         //写入内容至文件
         writeText(new FileOutputStream("D:\\hellocopy.txt"), "您好，读写文件一般都用字符流，这种方式不推荐！");
         //复制文件，上面写入文件内容不变
         writeText(new FileOutputStream("D:\\hellocopy.txt",true),readText(new FileInputStream("D:\\hello.txt")));
     }
     //用FileInputStream读取文件
     public static String readText(InputStream is){
         BufferedInputStream bis = null;
         String str = null;
         try {
             bis = new BufferedInputStream(is);
             int len = 0;
             byte[] by = new byte[1024];
             while((len=bis.read(by))!=-1){
                 str = new String(by,0,len);
             }
         } catch (Exception e) {
             // TODO: handle exception
             e.printStackTrace();
         }finally{
             try {
                 if(bis!=null){
                     bis.close();
                     return str;
                 }
             } catch (Exception e2) {
                 // TODO: handle exception
                 e2.printStackTrace();
             }
         }
         return str;
     }
     //用FileOutputStream写入文件
     public static void writeText(OutputStream os,String str){
         BufferedOutputStream bos = null;
         try {
             bos = new BufferedOutputStream(os);
             bos.write(str.getBytes());
         } catch (Exception e) {
             // TODO: handle exception
             e.printStackTrace();
         }finally{
             try{
             if(bos!=null){
                 bos.close();
             }
             }catch (Exception e) {
                 // TODO: handle exception
                 e.printStackTrace();
             }

         }

     }
 }

声明一下：一般读写文本文件均为字符流，笔者用字节流来写，推荐大家使用字符流读写文本文件。