java檔案讀寫操作大全

一.獲得控制台使用者輸入的資訊

     public String getInputMessage() throws IOException...{
         System.out.println("請輸入您的命令∶");
         byte buffer[]=new byte[1024];
         int count=System.in.read(buffer);
         char[] ch=new char[count-2];//最後兩位為結束符，刪去不要
         for(int i=0;i<count-2;i++)
             ch[i]=(char)buffer[i];
         String str=new String(ch);
         return str;
     }
     可以返回使用者輸入的資訊，不足之處在於不支援中文輸入，有待進一步改進。

     二.複製檔案
     1.以檔案流的方式複製檔案

     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();
     }
     該方法經過測試，支援中文處理，並且可以複製多種類型，比如txt，xml，jpg，doc等多種格式

     三.寫檔案

     1.利用PrintStream寫檔案

     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();
         }
     }
     2.利用StringBuffer寫檔案
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("這是第"+i+"行:前面介紹的各種方法都不關用,為什麼總是奇怪的問題 ");
             out.write(sb.toString().getBytes("utf-8"));
         }        
         out.close();
     }
     該方法可以設定使用何種編碼，有效解決中文問題。
四.檔案重新命名
    
     public void renameFile(String path,String oldname,String newname)...{
         if(!oldname.equals(newname))...{//新的檔案名稱和以前檔案名稱不同時,才有必要進行重新命名
             File oldfile=new File(path+"/"+oldname);
             File newfile=new File(path+"/"+newname);
             if(newfile.exists())//若在該目錄下已經有一個檔案和新檔案名稱相同，則不允許重新命名
                 System.out.println(newname+"已經存在！");
             else...{
                 oldfile.renameTo(newfile);
             }
         }         
     }

  五.轉移檔案目錄
     轉移檔案目錄不等同於複製檔案，複製檔案是複製後兩個目錄都存在該檔案，而轉移檔案目錄則是轉移後，只有新目錄中存在該檔案。
    
     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())...{//若在待轉移目錄下，已經存在待轉移檔案
                 if(cover)//覆蓋
                     oldfile.renameTo(newfile);
                 else
                     System.out.println("在新目錄下已經存在："+filename);
             }
             else...{
                 oldfile.renameTo(newfile);
             }
         }       
     }
     六.讀檔案
     1.利用FileInputStream讀取檔案
    
     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];//重建，避免和上次讀取的資料重複
         }
         return sb.toString();
     }
2.利用BufferedReader讀取

     在IO操作，利用BufferedReader和BufferedWriter效率會更高一點

    
     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();
     }

     3.利用dom4j讀取xml檔案

    
     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;
     }
     七.建立檔案(檔案夾)

1.建立檔案夾  
     public void createDir(String path)...{
         File dir=new File(path);
         if(!dir.exists())
             dir.mkdir();
     }
2.建立新檔案
     public void createFile(String path,String filename) throws IOException...{
         File file=new File(path+"/"+filename);
         if(!file.exists())
             file.createNewFile();
     }
     八.刪除檔案(目錄)
1.刪除檔案     
     public void delFile(String path,String filename)...{
         File file=new File(path+"/"+filename);
         if(file.exists()&&file.isFile())
             file.delete();
     }
2.刪除目錄
要利用File類的delete()方法刪除目錄時，必須保證該目錄下沒有檔案或者子目錄，否則刪除失敗，因此在實際應用中，我們要刪除目錄，必須利用遞迴刪除該目錄下的所有子目錄和檔案，然後再刪除該目錄。  
     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();
         }
     }

轉自:http://www.cnblogs.com/zhuocheng/archive/2011/12/12/2285290.html