how to replace strings in a file by other strings in java -

i have file every line contains strings :

usual,proper,complete,1,convenient,convenient,nonprob,recommended,recommend 

i want replace every word such code :

1000, 100, 110, 110, 111, 001, 111, 111, 1000 

here code used still incomplete :

public class codage {     bufferedreader in;      public codage() {         try {             in = new bufferedreader(new filereader("nursery.txt"));             fileoutputstream fos2 = new fileoutputstream("nursery.txt");             dataoutputstream output = new dataoutputstream(fos2);             string str;              while (null != ((str = in.readline()))) {                  string delims = ",";                 string[] tokens = str.split(delims);                 int tokencount = tokens.length;                 (int j = 0; j < tokencount; j++) {                     if (tokens[j].equals("usual")) {                         tokens[j] = "1000";                         output.writechars(tokens[j]);                      }                     //continue other cases                 }                 system.out.print(str);             }              in.close();          } catch (ioexception e) {              system.out.println("there problem:" + e);         }     }      public static void main(string[] args) {         codage c = new codage();     }  } 

my code replace values incorrectly.

first of all, code wrote here not working, because when open outputstream exact file try read from, empty source file , statement in.readline() returns null. if real code maybe problem.

i assume know should separate file opening read , 1 want write into. is, when open nursery.txt read from, should create outputstream temp file called nursery.tmp in same path, , after process finished, can delete nursery.txt , rename nursery.tmp nursery.txt.

also if you, wouldn't job using if-else structure. seams have unique keys like:

usual, proper, complete, convenient, convenient, nonprob, recommended, recommend

so maybe more convenient use map structure lookup replacing value:

usual, proper, complete, convenient, convenient, nonprob, recommended, recommend, ...

1000, 100, 110, 110, 111, 001, 111, 111, ...

but these guesses , know how manage business logic.

after part think better idea create output data string lines , write them line line nursery.tmp:

public class codage {      private bufferedreader in;     private bufferedwriter out;      private hashmap<string, string> replacingvaluesbykeys = new hashmap<string, string>();      public codage() {         initialize();     }      private void initialize() {         // assumed have rule key "proper" goes "100"         // initialize map between keys , replacing values:          replacingvaluesbykeys.put("usual", "1000");         replacingvaluesbykeys.put("proper", "100");         replacingvaluesbykeys.put("complete", "110");         replacingvaluesbykeys.put("convenient", "110");         replacingvaluesbykeys.put("nonprob", "111");         replacingvaluesbykeys.put("recommended", "001");         replacingvaluesbykeys.put("recommend", "1000");     }      public void dorelpacementinfile(){         try {             in = new bufferedreader(new filereader("c:/nursery.txt"));             out = new bufferedwriter(new filewriter("c:/nursery.tmp"));              string str = in.readline();             while (null != str) {                 iterator<string> = replacingvaluesbykeys.keyset().iterator();                 while(it.hasnext())                 {                     string tobereplaced = it.next();                     string replacementvalue = replacingvaluesbykeys.get(tobereplaced);                     // \\b word boundary, because have both recommend , recommended                     //        , not want replacing [recommend] part of recommended.                     str = str.replaceall("\\b"+tobereplaced+"\\b", replacementvalue);                 }                 // write replaced line temp file:                 out.append(str);                 out.newline();                  // not forget read next line:                 str = in.readline();             }          } catch (ioexception e) {             system.out.println("there problem:" + e);         } finally{             try {                 in.close();                 out.close();             } catch (ioexception e) {                 e.printstacktrace();             }         }           file f = new file("c:/nursery.txt");         f.delete();          file f2 = new file("c:/nursery.tmp");         f2.renameto(new file("c:/nursery.txt"));     }       public static void main(string[] args) {         codage c = new codage();         c.dorelpacementinfile();     }  } 

hope snippets helpful,

good luck.