java文件读写操作大全

public String getInputMessage() throws IOException...{
    System.out.println("请输入您的命令∶");
    byte buffer[]=new byte[1024];
    int count=System.in.read(buffer);
    char[] ch=new char[count-2];//最后两位为结束符，删去不要
    for(int i=0;i<count-2;i++)
        ch[i]=(char)buffer[i];
    String str=new String(ch);
    return str;
}
可以返回用户输入的信息，不足之处在于不支持中文输入，有待进一步改进。

public void copyFile(String src,String dest) throws IOException...{
    FileInputStream in=new FileInputStream(src);
    File file=new File(dest);
    if(!file.exists())
        file.createNewFile();
    FileOutputStream out=new FileOutputStream(file);
    int c;
    byte buffer[]=new byte[1024];
    while((c=in.read(buffer))!=-1)...{
        for(int i=0;i<c;i++)
            out.write(buffer[i]);        
    }
    in.close();
    out.close();
}

public void PrintStreamDemo()...{
    try ...{
        FileOutputStream out=new FileOutputStream("D:/test.txt");
        PrintStream p=new PrintStream(out);
        for(int i=0;i<10;i++)
            p.println("This is "+i+" line");
    } catch (FileNotFoundException e) ...{
        e.printStackTrace();
    }
}

public void StringBufferDemo() throws IOException......{
         File file=new File("/root/sms.log");
         if(!file.exists())
             file.createNewFile();
         FileOutputStream out=new FileOutputStream(file,true);        
         for(int i=0;i<10000;i++)......{
             StringBuffer sb=new StringBuffer();
             sb.append("这是第"+i+"行:前面介绍的各种方法都不关用,为什么总是奇怪的问题 ");
             out.write(sb.toString().getBytes("utf-8"));
         }        
         out.close();
     }

public void renameFile(String path,String oldname,String newname)...{
    if(!oldname.equals(newname))...{//新的文件名和以前文件名不同时,才有必要进行重命名
        File oldfile=new File(path+"/"+oldname);
        File newfile=new File(path+"/"+newname);
        if(newfile.exists())//若在该目录下已经有一个文件和新文件名相同，则不允许重命名
            System.out.println(newname+"已经存在！");
        else...{
            oldfile.renameTo(newfile);
        }
    }         
}

public void changeDirectory(String filename,String oldpath,String newpath,boolean cover)...{
    if(!oldpath.equals(newpath))...{
        File oldfile=new File(oldpath+"/"+filename);
        File newfile=new File(newpath+"/"+filename);
        if(newfile.exists())...{//若在待转移目录下，已经存在待转移文件
            if(cover)//覆盖
                oldfile.renameTo(newfile);
            else
                System.out.println("在新目录下已经存在："+filename);
        }
        else...{
            oldfile.renameTo(newfile);
        }
    }       
}

public String FileInputStreamDemo(String path) throws IOException...{
    File file=new File(path);
    if(!file.exists()||file.isDirectory())
        throw new FileNotFoundException();
    FileInputStream fis=new FileInputStream(file);
    byte[] buf = new byte[1024];
    StringBuffer sb=new StringBuffer();
    while((fis.read(buf))!=-1)...{
        sb.append(new String(buf));    
        buf=new byte[1024];//重新生成，避免和上次读取的数据重复
    }
    return sb.toString();
}

public String BufferedReaderDemo(String path) throws IOException...{
    File file=new File(path);
    if(!file.exists()||file.isDirectory())
        throw new FileNotFoundException();
    BufferedReader br=new BufferedReader(new FileReader(file));
    String temp=null;
    StringBuffer sb=new StringBuffer();
    temp=br.readLine();
    while(temp!=null)...{
        sb.append(temp+" ");
        temp=br.readLine();
    }
    return sb.toString();
}

public Document readXml(String path) throws DocumentException, IOException...{
    File file=new File(path);
    BufferedReader bufferedreader = new BufferedReader(new FileReader(file));
    SAXReader saxreader = new SAXReader();
    Document document = (Document)saxreader.read(bufferedreader);
    bufferedreader.close();
    return document;
}

public void createDir(String path)...{
    File dir=new File(path);
    if(!dir.exists())
        dir.mkdir();
}

public void createFile(String path,String filename) throws IOException...{
    File file=new File(path+"/"+filename);
    if(!file.exists())
        file.createNewFile();
}

public void delFile(String path,String filename)...{
    File file=new File(path+"/"+filename);
    if(file.exists()&&file.isFile())
        file.delete();
}

public void delDir(String path)...{
    File dir=new File(path);
    if(dir.exists())...{
        File[] tmp=dir.listFiles();
        for(int i=0;i<tmp.length;i++)...{
            if(tmp[i].isDirectory())...{
                delDir(path+"/"+tmp[i].getName());
            }
            else...{
                tmp[i].delete();
            }
        }
        dir.delete();
    }
}