• java文件读写操作大全


    一.获得控制台用户输入的信息

         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。

         二.复制文件
         1.以文件流的方式复制文件

         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();
         }
         该方法经过测试,支持中文处理,并且可以复制多种类型,比如txt,xml,jpg,doc等多种格式

         三.写文件

         1.利用PrintStream写文件


         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写文件
    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();
         }
         该方法可以设定使用何种编码,有效解决中文问题。
    四.文件重命名
        
         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);
                 }
             }         
         }

      五.转移文件目录
         转移文件目录不等同于复制文件,复制文件是复制后两个目录都存在该文件,而转移文件目录则是转移后,只有新目录中存在该文件。
        
         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);
                 }
             }       
         }
         六.读文件
         1.利用FileInputStream读取文件

        
         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();
         }
    2.利用BufferedReader读取

         在IO操作,利用BufferedReader和BufferedWriter效率会更高一点


        
         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读取xml文件

        
         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.创建文件(文件夹)


    1.创建文件夹  
         public void createDir(String path)...{
             File dir=new File(path);
             if(!dir.exists())
                 dir.mkdir();
         }
    2.创建新文件
         public void createFile(String path,String filename) throws IOException...{
             File file=new File(path+"/"+filename);
             if(!file.exists())
                 file.createNewFile();
         }
         八.删除文件(目录)
    1.删除文件     
         public void delFile(String path,String filename)...{
             File file=new File(path+"/"+filename);
             if(file.exists()&&file.isFile())
                 file.delete();
         }
    2.删除目录
    要利用File类的delete()方法删除目录时,必须保证该目录下没有文件或者子目录,否则删除失败,因此在实际应用中,我们要删除目录,必须利用递归删除该目录下的所有子目录和文件,然后再删除该目录。  
         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();
             }
         }

    From zhuocheng (cnblogs.com/zhuocheng)
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  • 原文地址:https://www.cnblogs.com/avivahe/p/5658260.html
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