[Datastructure] A useful util class for reading and writing files

Faced with the upcoming exam, some useful methods referred to file operation drew tremenous attention. Now I make a summary to reading file.

Import Java. io. bufferedreader; import Java. io. bufferedwriter; import Java. io. file; import Java. io. fileinputstream; import Java. io. filenotfoundexception; import Java. io. fileoutputstream; import Java. io. ioexception; import Java. io. inputstreamreader; import Java. io. outputstreamwriter; import Java. util. arraylist; import Java. util. hashmap; import Java. util. list; import Java. util. map; public class fileutil {public St Atic final string Sep = ":"; public static final string encoding = "UTF-8";/*** read the content from file, the format of content is like "key: value "* todo ** @ time Jul 17,201 4 11:21:50 am * @ Param filepath * @ return * @ throws exception * @ return Map <string, string> */public static Map <string, string> readfiletomap (string filepath) throws exception {system. out. println ("Read File [" + filepath + "] On Start... "); Map <string, string> contents = new hashmap <string, string> (); file = new file (filepath); bufferedreader reader = NULL; try {reader = new bufferedreader (New inputstreamreader (New fileinputstream (file), encoding); string info = NULL; while (Info = reader. readline ())! = NULL) {contents. put (info. split (SEP) [0], info. split (SEP) [1]) ;}} catch (filenotfoundexception e) {system. out. println ("file [" + filepath + "] Not found. "); throw E;} catch (ioexception e) {system. out. println ("file IO operation error, exception information:" + E. getmessage (); throw E;} catch (exception e) {system. out. println ("file read error, exception information:" + E. getmessage (); throw E;} finally {If (reader! = NULL) {try {reader. close ();} catch (ioexception e) {system. out. println ("An error occurred while disabling the IO stream. Exception information:" + E. getmessage (); throw e ;}} system. out. println ("Read File [" + filepath + "] ends. "); Return contents;}/*** read the content from file, every line will be an element of list. ** @ time Jul 17,201 4 11:39:07 am * @ Param filename * @ return list <string> */public static list <string> readfiletolist (S Tring filename) throws exception {list <string> Infos = new arraylist <string> (); bufferedreader reader = NULL; try {reader = new bufferedreader (New inputstreamreader (New fileinputstream (new file (filename), "UTF-8"); string info = NULL; while (Info = reader. readline ())! = NULL) {Infos. add (Info) ;}} catch (filenotfoundexception e) {system. out. println ("file [" + filename + "] Not found. "); throw E;} catch (ioexception e) {system. out. println ("file IO operation error, exception information:" + E. getmessage (); throw E;} finally {try {If (reader! = NULL) {reader. close () ;}} catch (ioexception e) {e. printstacktrace () ;}} return Infos;}/*** read all the content from filepath at a time. ** @ time Jul 17,201 4 11:45:55 am * @ Param filepathorfilename * @ return string */public static string readfiletostring (string filepath) throws exception {inputstreamreader isreder = NULL; bufferedreader BR = NULL; stringbuffer sb = new strin Gbuffer (); try {file F = new file (filepath); If (F. isfile () & F. exists () {isreder = new inputstreamreader (New fileinputstream (F), "UTF-8"); BR = new bufferedreader (isreder); string line; while (line = BR. readline ())! = NULL) {sb. append (line ). append ("\ r \ n") ;}} catch (exception e) {system. out. println ("exception when reading the file" + filepath); throw E;} finally {If (isreder! = NULL) {try {isreder. Close () ;}catch (ioexception e) {e. getmessage () ;}} if (BR! = NULL) {try {BR. close ();} catch (ioexception e) {e. getmessage () ;}} return sb. tostring ();} /*** Write result to the filename ** @ time Jul 17,201 4 4:57:57 * @ Param result * @ Param filename * @ return void */public static void writefile (string result, string filename) {file F = new file (filename); outputstreamwriter OSW = NULL; bufferedwriter BW = NULL; try {If (! F. exists () {f. createnewfile ();} OSW = new outputstreamwriter (New fileoutputstream (F), "UTF-8"); // "GBK" BW = new bufferedwriter (OSW); BW. write (result);} catch (ioexception e) {system. out. println ("ioexception when writing result," + E. getmessage ();} catch (exception e) {system. out. println ("exception when writing result," + E. getmessage ();} finally {If (BW! = NULL) {try {BW. close ();} catch (ioexception e) {system. out. println ("ioexception when closing filewriter," + E. getmessage () ;}} if (OSW! = NULL) {try {OSW. close ();} catch (ioexception e) {system. out. println ("ioexception when closing bufferwriter," + E. getmessage () ;}}} public static void main (string [] ARGs) throws exception {Map <string, string> testmap = fileutil. readfiletomap ("input.txt"); system. out. println ("---------------------"); For (map. entry <string, string> entry: testmap. entryset () {system. out. println (entry. getkey () + ":" + entry. getvalue ();} system. out. println ("---------------------"); List <string> testlist = fileutil. readfiletolist ("input.txt"); For (string STR: testlist) {system. out. println (STR);} system. out. println ("---------------------"); string test = fileutil. readfiletostring ("input.txt"); fileutil. writefile (test, "output.txt ");}}