Operations on files in Java

Operations on files in Java

Java provides I/O class libraries, allowing you to easily perform operations on files using Java. The following describes how to use Java to implement these operations.

1. Create directory

<% @ Page contenttype = "text/html; charset = gb2312" %>

<%

String filepath = "C:/AAA /";

Filepath = filepath. tostring (); // Chinese Conversion

Java. Io. File myfilepath = new java. Io. File (filepath );

If (! Myfilepath. exists ())

Myfilepath. mkdir ();

%>

2. Create a file

<% @ Page contenttype = "text/html; charset = gb2312" %>

<% @ Page import = "Java. Io. *" %>

<%

String filepath = "C:/harhat.txt ";

Filepath = filepath. tostring ();

File myfilepath = new file (filepath );

If (! Myfilepath. exists ())

Myfilepath. createnewfile ();

Filewriter resultfile = new filewriter (myfilepath );

Printwriter myfile = new printwriter (resultfile );

String strcontent = "Chinese test". tostring ();

Myfile. println (strcontent );

Resultfile. Close ();

%>

3. Delete an object

<% @ Page contenttype = "text/html; charset = gb2312" %>

<%

String filepath = "C:/withdrawal ticket .xls ";

Filepath = filepath. tostring ();

Java. Io. File mydelfile = new java. Io. File (filepath );

Mydelfile. Delete ();

%>

4. File copy

<% @ Page contenttype = "text/html; charset = gb2312" %>

<% @ Page import = "Java. Io. *" %>

<%

Int bytesum = 0;

Int byteread = 0;

File: // read to the stream

Inputstream instream = new fileinputstream ("C:/aaa.doc ");

Fileoutputstream FS = new fileoutputstream ("D:/aaa.doc"); byte [] buffer = new byte [1444];

Int length;

While (byteread = instream. Read (buffer ))! =-1)

{

Out. println ("<DT> <B>" + byteread + "</B> </DT> ");

Bytesum + = byteread;

System. Out. println (bytesum );

FS. Write (buffer, 0, byteread );

}

Instream. Close ();

%>

5. Copy the entire folder

<% @ Page contenttype = "text/html; charset = gb2312" %>

<% @ Page import = "Java. Io. *" %>

<% String url1 = "C:/AAA ";

String url2 = "D:/Java /";

(New file (url2). mkdirs ();

File [] file = (new file (url1). listfiles ();

For (INT I = 0; I <file. length; I ++ ){

If (file [I]. isfile ()){

File [I]. tostring ();

Fileinputstream input = new fileinputstream (file [I]);

Fileoutputstream output = new fileoutputstream (url2 + "/" + (file [I]. getname (). tostring ());

Byte [] B = new byte [1, 1024*5];

Int Len;

While (LEN = input. Read (B ))! =-1 ){

Output. Write (B, 0, Len );

}

Output. Flush ();

Output. Close ();

Input. Close ();

}

}

%>

6. File Download

<% @ Page contenttype = "text/html; charset = gb2312" %>

<% @ Page import = "Java. Io. *" %>

<%

String filename = "zsc104.swf". tostring ();

// Reading the stream

Inputstream instream = new fileinputstream ("C:/zsc104.swf ");

// Set the output format

Response. Reset ();

Response. setcontenttype ("bin ");

Response. addheader ("content-disposition", "attachment; filename = \" "+ filename + "\"");

// Cyclically retrieve the data in the stream

Byte [] B = new byte [100];

Int Len;

While (LEN = instream. Read (B)> 0)

Response. getoutputstream (). Write (B, 0, Len );

Instream. Close ();

%>

7. Download files from database fields

<% @ Page contenttype = "text/html; charset = gb2312" %>

<% @ Page import = "Java. SQL. *" %>

<% @ Page import = "Java. Lang. *" %>

<% @ Page import = "Java. Io. *" %>

<% @ Page import = "com. jspsmart. Upload. *" %>

<% @ Page import = "dbstep. idbmanager2000. *" %>

<%

Int bytesum = 0;

Int byteread = 0;

// Open the database

Resultset result = NULL;

String SQL = NULL;

Preparedstatement prestmt = NULL;

Dbstep. idbmanager2000 dbaobj = new dbstep. idbmanager2000 ();

Dbaobj. openconnection ();

// Obtain data in the database

SQL = "select * From t_local_zhongzhuan ";

Result = dbaobj. executequery (SQL );

Result. Next ();

File: // read data from the database to the stream

Inputstream instream = result. getbinarystream ("content ");

Fileoutputstream FS = new fileoutputstream ("C:/dffdsafd.doc ");

Byte [] buffer = new byte [1444];

Int length;

While (byteread = instream. Read (buffer ))! =-1)

{

Out. println ("<DT> <B>" + byteread + "</B> </DT> ");

Bytesum + = byteread;

System. Out. println (bytesum );

FS. Write (buffer, 0, byteread );

}

%>

8. Save a webpage as a file

<% @ Page import = "Java. Text. *" %>

<% @ Page import = "Java. util. *" %>

<% @ Page import = "Java. Io. *" %>

<% @ Page import = "java.net. *" %>

<%

URL stdurl = NULL;

Bufferedreader stdin = NULL;

Printwriter stdout = NULL;

Try {

Stdurl = new URL ("http://www.163.com ");

}

Catch (malformedurlexception e ){

Throw E;

}

Try {

Stdin = new bufferedreader (New inputstreamreader (stdurl. openstream ()));

Stdout = new printwriter (New bufferedwriter (New filewriter ("C:/163.html ")));

}

Catch (ioexception e ){

}

/*** Read the page specified by the URL as a stream and write it as a specified file ***/

Try {

String strhtml = "";

While (strhtml = stdin. Readline ())! = NULL ){

Stdout. println (strhtml );

}

}

Catch (ioexception e ){

Throw E;

}

Finally {

Try {

If (stdin! = NULL)

Stdin. Close ();

If (stdout! = NULL)

Stdout. Close ();

}

Catch (exception e ){

System. Out. println (E );

}

}

%>

9. Download online files directly

<% @ Page import = "Java. Io. *" %>

<% @ Page import = "java.net. *" %>

<%

Int bytesum = 0;

Int byteread = 0;

URL url = new URL ("http://pimg.163.com/sms/micheal/logo.gif ");

Urlconnection conn = URL. openconnection ();

Inputstream instream = conn. getinputstream ();

Fileoutputstream FS = new fileoutputstream ("C:/abc.gif ");

Byte [] buffer = new byte [1444];

Int length;

While (byteread = instream. Read (buffer ))! =-1)

{

Out. println ("<DT> <B>" + byteread + "</B> </DT> ");

Bytesum + = byteread;

System. Out. println (bytesum );

FS. Write (buffer, 0, byteread );

}

%>

10. Read files by row

<% @ Page contenttype = "text/html; charset = gb2312" %>

<% @ Page import = "Java. Io. *" %>

<% Filereader myfilereader = new filereader ("C:/ha.txt .txt ");

Bufferedreader mybufferedreader = new bufferedreader (myfilereader );

String mystring = NULL;

String resultstring = new string ();

While (mystring = mybufferedreader. Readline ())! = NULL) {resultstring = resultstring + mystring + "<br> ";}

Out. println (resultstring); myfilereader. Close ();

%>