java文件读写操作大全

来自：http://blog.sina.com.cn/s/blog_4fd11d0a0100xll5.html

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();
?????????}
?????}