Java I/O classic code example

Package IO; import java. Io. *; public class filedirectorydemo {public static void main (string [] ARGs) {// if no parameter is specified, the default value is the current directory. If (ARGs. Length = 0) {ARGs = new string [] {"." };}try {// create a file object in the specified directory. File currentpath = new file (ARGs [0]); // create a file object in the temp directory in the specified directory. File temppath = new file (currentpath, "Temp"); // use the "temppath" object to create the temp directory under the specified directory. Temppath. mkdir (); // create two files in the temp directory. File temp1 = new file (temppath, "temp1.txt"); temp1.createnewfile (); file temp2 = new file (temppath, "temp2.txt"); temp2.createnewfile (); // recursively display the content of the specified directory. System. Out. println ("display the content of the specified directory"); listsubdir (currentpath); // modify the file name to "temp1.txtworkflow ". File temp1new = new file (temppath, "temp.txt"); temp1.renameto (temp1new); // recursively display the contents of the temp subdirectory. System. Out. println ("show temp sub-directory content after file name change"); listsubdir (temppath); // Delete the “temp2.txt file ". Temp2.delete (); // recursively display the contents of the temp sub-directory. System. out. println ("the contents of the temp subdirectory are displayed after the file is deleted"); listsubdir (temppath);} catch (ioexception e) {system. err. println ("ioexception") ;}// recursively display the content of the specified directory. Static void listsubdir (File currentpath) {// gets the list of contents in the specified directory. String [] filenames = currentpath. list (); try {for (INT I = 0; I <filenames. length; I ++) {file F = new file (currentpath. getpath (), filenames [I]); // if it is a directory, the directory NAME IS DISPLAYED, recursively called, and the sub-directory content is displayed. If (F. isdirectory () {// display the directory in a standard path format. System. Out. println (F. GetCanonicalPath (); // recursively calls and displays subdirectories. Listsubdir (f);} // if it is a file, the file name is displayed, excluding the path information. Else {system. out. println (F. getname () ;}} catch (ioexception e) {system. err. println ("ioexception") ;}} package IO; import Java. io. *; public class fileexample {public fileexample () {super (); // call the constructor of the parent class} public static void main (string [] ARGs) {try {string OUTFILE = "demoout. XML "; // defines a variable used to identify the output file string infile =" demoin. XML "; // defines a variable used to identify the input file dataoutputstream dt = new dataoutpu Tstream (New bufferedoutputstream (New fileoutputstream (OUTFILE);/*** use fileoutputstream to define an input stream file, * Then use buferedoutputstream to call the fileoutputstream object to generate a buffer output stream * Then use dataoutputstream to call the buferedoutputstream object to generate a data formatting output stream */bufferedwriter newfile = new bufferedwriter, "GBK"); // processing of Chinese data datainputstream raffile1 = new datainputstream (New bufferedinputstream (New fileinputstream (infil E);/*** use fileinputstream to define an input stream file. * Then use buferedinputstream to call the fileinputstream object to generate a buffer output stream *, then, use datainputstream to call the buferedinputstream object to generate a data formatted output stream */bufferedreader raffile = new bufferedreader (New inputstreamreader (raffile1, "GBK ")); // processing of Chinese Characters String xmlcontent = ""; char tag = 0; // The file ends with zero characters while (tag! = (Char) (-1) {xmlcontent = xmlcontent + tag + raffile. readline () + '';} newfile. write (xmlcontent); newfile. flush (); // clear the newfile buffer. close (); raffile. close (); system. GC (); // force immediate garbage collection to release the memory.} Catch (nullpointerexception exc) {exc. printstacktrace ();} catch (Java. lang. indexoutofboundsexception outb) {system. out. println (outb. getmessage (); outb. printstacktrace ();} catch (filenotfoundexception Fex) {system. out. println ("Fex" + Fex. getmessage ();} catch (ioexception iex) {system. out. println ("iex" + iex. getmessage () ;}} package IO; import Java. io. *; public class filerandomrw {// The number of persons to be entered. Public static int number = 3; public static void main (string [] ARGs) {persons [] People = new persons [number]; people [0] = new persons ("Zhang Feng", 26,200 0, "N"); People [1] = new persons ("yanna", 25,500 00, "Y"); People [2] = new persons ("Li Peng", 50,700 0, "F"); try {dataoutputstream out = new dataoutputstream (New fileoutputstream ("peoplerandom. dat "); // Save the personnel data to" peoplerandom. dat. Writedata (people, out); // close the stream. Out. Close (); // read data in reverse order from the binary file "peoplerandom. dat. Randomaccessfile inout = new randomaccessfile ("peoplerandom. dat", "RW"); persons [] inpeople = readdatareverse (inout); // output the read data. System. out. println ("Raw data:"); For (INT I = 0; I <inpeople. length; I ++) {system. out. println (inpeople [I]);} // modify the third record of the file. Inpeople [2]. setsalary (4500); // write the Modification result to a file. Inpeople [2]. writedata (inout, 3); // close the stream. Inout. Close (); // The third record read from the file and output it to verify the Modification result. Randomaccessfile in = new randomaccessfile ("peoplerandom. dat", "R"); Persons in3people = new persons (); // read the third record randomly. In3people. readdata (in, 3); // close the stream. In. close (); system. out. println ("modified records"); system. out. println (in3people);} catch (ioexception exception) {system. err. println ("ioexception") ;}// write data to the output stream. Static void writedata (persons [] P, dataoutputstream out) throws ioexception {for (INT I = 0; I <p. length; I ++) {P [I]. writedata (out) ;}// reads data from the input stream in reverse order. Static persons [] readdatareverse (randomaccessfile in) throws ioexception {// obtain the number of records. Int record_num = (INT) (IN. Length ()/persons. record_length); persons [] P = new persons [record_num]; // reads data in reverse order. For (INT I = record_num-1; I> = 0; I --) {P [I] = new persons (); // locate the file. In. seek (I * persons. record_length); P [I]. readdata (in, I + 1);} return P ;}} class persons {private string name; private int age; // 4 bytes private double salary; // eight bytes private string married; public static final int name_length = 20; // Name Length public static final int married_length = 2; // marital status length public static final int record_length = name_length * 2 + 4 + 8 + married_length * 2; public persons () {} Public persons (string N, int A, double S) {name = N; age = A; salary = s; married = "F";} public persons (string N, int A, double S, string m) {name = N; age = A; salary = s; married = m;} Public String getname () {return name ;} public int getage () {return age;} public double getsalary () {return salary;} Public String getmarried () {return married;} Public String setname (string N) {n Ame = N; return name;} public int setage (int A) {age = A; return age;} public double setsalary (double S) {salary = s; return salary ;} public String setmarried (string m) {married = m; return married;} // set the output format. Public String tostring () {return getclass (). getname () + "[name =" + name + ", age =" + age + ", salary =" + salary + ", married = "+ Married +"] ";} // write a fixed-length record, that is, a person's data to the output stream. Public void writedata (dataoutput out) throws ioexception {fixstringio. writefixstring (name, name_length, out); out. writeint (AGE); out. writedouble (salary); fixstringio. writefixstring (married, married_length, out);} // write a fixed-length record to the random read file. Private void writedata (randomaccessfile out) throws ioexception {fixstringio. writefixstring (name, name_length, out); out. writeint (AGE); out. writedouble (salary); fixstringio. writefixstring (married, married_length, out);} // randomly write a fixed-length record to the specified position of the output stream. Public void writedata (randomaccessfile out, int N) throws ioexception {out. seek (n-1) * record_length); writedata (out);} // randomly reads a record from the input stream, that is, a person's data. Private void readdata (randomaccessfile in) throws ioexception {name = fixstringio. readfixstring (name_length, In); age = in. readint (); salary = in. readdouble (); married = fixstringio. readfixstring (married_length, In);} // randomly reads records at the specified position from the input stream. Public void readdata (randomaccessfile in, int N) throws ioexception {In. seek (n-1) * record_length); readdata (in );}} // read and write fixed-length Unicode strings from the file class fixstringio {// read the fixed-length Unicode string. Public static string readfixstring (INT size, datainput in) throws ioexception {stringbuffer B = new stringbuffer (size); int I = 0; Boolean more = true; while (more & I <size) {char CH = in. readchar (); I ++; If (CH = 0) {more = false;} else {B. append (CH) ;}// skip the remaining bytes. In. skipbytes (2 * (size-I); return B. tostring () ;}// write a fixed-length Unicode string. Public static void writefixstring (string S, int size, dataoutput out) throws ioexception {int I; for (I = 0; I <size; I ++) {char CH = 0; if (I <S. length () {CH = S. charat (I);} Out. writechar (CH) ;}} package IO; import Java. io. *; import Java. util. *; public class filerw {// number of persons to be entered. Public static int number = 3; public static void main (string [] ARGs) {person [] People = new person [number]; // temporary string array that temporarily holds the input data. String [] field = new string [4]; // initialize the field array. For (INT I = 0; I <4; I ++) {field [I] = "" ;}// Io operations must capture Io exceptions. Try {// adds control to the field array. Int fieldcount = 0; // use system. In to construct inputstreamreader and then bufferedreader. Bufferedreader stdin = new bufferedreader (New inputstreamreader (system. in); For (INT I = 0; I <number; I ++) {fieldcount = 0; system. out. println ("the number" + (I + 1) + "person"); system. out. println ("Enter name, age, salary, married (optional), please separate fields by ':'"); // read a row. String personstr = stdin. Readline (); // you can specify the delimiter. Stringtokenizer ST = new stringtokenizer (personstr, ":"); // you can determine whether a separator is available. While (St. hasmoretokens () {field [fieldcount] = ST. nexttoken (); fieldcount ++;} // if married is input, field [3] is not blank and the person constructor with four parameters is called. If (field [3]! = "") {People [I] = new person (field [0], integer. parseint (field [1]), double. parsedouble (field [2]), field [3]); // leave field [3] Blank for future input. Field [3] = "";} // if married is not input, field [3] Is null and the person constructor with three parameters is called. Else {People [I] = new person (field [0], integer. parseint (field [1]), double. parsedouble (field [2]) ;}// Save the input data to "people. dat. Printwriter out = new printwriter (New bufferedwriter (New filewriter ("People. dat"); writedata (people, out); // close the stream. Out. Close (); // read data from the file "People. dat. Bufferedreader in = new bufferedreader (New filereader ("People. dat"); person [] inpeople = readdata (in); // close the stream. In. Close (); // output the data read from the file. For (INT I = 0; I <inpeople. length; I ++) {system. out. println (inpeople [I]);} catch (ioexception exception) {system. err. println ("ioexception") ;}// write all data to the output stream. Static void writedata (person [] P, printwriter out) throws ioexception {// Number of write records, that is, the number of people. Out. println (P. length); For (INT I = 0; I <p. length; I ++) {P [I]. writedata (out) ;}// read all data from the input stream. Static person [] readdata (bufferedreader in) throws ioexception {// obtain the number of records, that is, the number of people. Int n = integer. parseint (in. readline (); person [] P = new person [N]; for (INT I = 0; I <n; I ++) {P [I] = new person (); P [I]. readdata (in) ;}return P ;}} class person {private string name; private int age; private double salary; private string married; Public Person () {} public person (string N, int A, double S) {name = N; age = A; salary = s; married = "F";} public person (string N, int A, Dou Ble S, string m) {name = N; age = A; salary = s; married = m;} Public String getname () {return name;} public int getage () {return age;} public double getsalary () {return salary;} Public String getmarried () {return married;} // you can specify the output format. Public String tostring () {return getclass (). getname () + "[name =" + name + ", age =" + age + ", salary =" + salary + ", married = "+ Married +"] ";} // write a record, that is, a person's data to the output stream. Public void writedata (printwriter out) throws ioexception {// format the output. Out. println (name + ":" + age + ":" + salary + ":" + married) ;}// read a record from the input stream, that is, a person's data. Public void readdata (bufferedreader in) throws ioexception {string S = in. readline (); stringtokenizer T = new stringtokenizer (S, ":"); name = T. nexttoken (); age = integer. parseint (T. nexttoken (); salary = double. parsedouble (T. nexttoken (); married = T. nexttoken () ;}} package IO; import Java. io. ioexception; public class filestdread {public static void main (string [] ARGs) throws ioexception {int B = 0; char c = ''; system. Out. println (" Enter: "); While (C! = 'Q') {int A = system. in. read (); C = (char) A; B ++; system. out. println (char) A);} system. err. print ("counted" + B + "totalbytes. ") ;}} // read the input data until the Letter Q exists in the data, then package IO; import Java. io. *; public class iostreamexample {public static void main (string [] ARGs) throws ioexception {// 1. read a row of data: bufferedreader in = new bufferedreader (New filereader ("filestdread. java "); string S, S2 = New String (); While (S = in. Readline ())! = NULL) {S2 + = S + "";} In. close (); bufferedreader stdin = new bufferedreader (New inputstreamreader (system. in); system. out. print ("enter a line:"); system. out. println (stdin. readline (); // 2. read stringreader in2 = new stringreader (S2); int C; while (C = in2.read () from memory ())! =-1) {system. out. print (char) C);} // 3. format the memory input try {datainputstream in3 = new datainputstream (New bytearrayinputstream (s2.getbytes (); While (true) {system. out. print (char) in3.readbyte () ;}} catch (eofexception e) {system. err. println ("End of stream");} // 4. file input try {bufferedreader in4 = new bufferedreader (New stringreader (S2); printwriter out1 = new printwriter (New bufferedwriter (New filewriter ("iodemo. Out"); int linecount = 1; while (S = in4.readline ())! = NULL) {out1.println (linecount ++ ":" + S) ;}out1.close () ;}catch (eofexception e) {system. err. println ("End of stream");} // 5. receiving and saving data try {dataoutputstream out2 = new dataoutputstream (New bufferedoutputstream (New fileoutputstream ("data.txt"); out2.writedouble (3.14159); out2.writeutf ("that was Pi "); out2.writedouble (1.41413); out2.writeutf ("square root of 2"); out2.close (); datainputst Ream in5 = new datainputstream (New bufferedinputstream (New fileinputstream ("data.txt"); system. out. println (in5.readdouble (); system. out. println (in5.readutf (); system. out. println (in5.readdouble (); system. out. println (in5.readutf ();} catch (eofexception e) {Throw new runtimeexception (E);} // 6. random reading of file content randomaccessfile Rf = new randomaccessfile ("rtest. dat "," RW "); For (INT I = 0; I <10; I ++) {Rf. writedouble (I * 1.414);} RF. close (); Rf = new randomaccessfile ("rtest. dat "," RW "); RF. seek (5*8); RF. writedouble (1, 47.0001); RF. close (); Rf = new randomaccessfile ("rtest. dat "," R "); For (INT I = 0; I <10; I ++) {system. out. println ("value" + I + ":" + RF. readdouble ();} RF. close () ;}} package IO; import Java. io. *;/*** <p> * Title: Java advanced tips * </P> ** Zhang Feng * 1.0 */public class makedir Ectoriesexample {Private Static void fileattrib (file F) {system. out. println ("absolute path:" + F. getabsolutepath () + "readable attribute:" + F. canread () + "customizable attributes:" + F. canwrite () + "file name:" + F. getname () + "parent directory:" + F. getparent () + "current path:" + F. getpath () + "file length:" + F. length () + "Last Updated Date:" + F. lastmodified (); If (F. isfile () {system. out. println ("input is a file");} else if (F. isdirectory () {system. out. println (" The input is a directory ") ;}} public static void main (string [] ARGs) {If (ARGs. length <1) {ARGs = new string [3];} ARGs [0] = "D"; ARGs [1] = "test1.txt "; ARGs [2] = "test2.txt"; file old = new file (ARGs [1]), rname = new file (ARGs [2]); old. renameto (rname); fileattrib (old); fileattrib (rname); int COUNT = 0; Boolean del = false; If (ARGs [0]. equals ("D") {count ++; del = true ;}count --; while (++ count <args. leng Th) {file F = new file (ARGs [count]); If (F. exists () {system. out. println (F + "file already exists"); If (DEL) {system. out. println ("delete file" + F); F. delete () ;}} else {// if the object does not exist if (! Del) {f. mkdirs (); system. Out. println ("Create File:" + F) ;}} fileattrib (f );}}}