java - Find String and replace it in the text document -

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i trying replace ? question marker - hyphen in text document being found not replaced

bad schwartau ? stockelsdorf ? zob/hbf. ? sandstr. ? universitätsklinikum ? grillenweg   9 haltestellen montag ? freitag bad schwartau/zob ... 04:21 04:54 05:40 06:03 06:18 06:33 06:48 07:03 07:21 07:33 08:03 11:03 

code:

try {     scanner = new scanner(file);      int linenum = 0;     while (scanner.hasnextline()) {         string line = scanner.nextline();         linenum++;         if(line.contains("?")) {              line.replace("?", "-");             system.out.println("i found on line " + linenum);         }     } }  

a java string immutable - means cannot changed, replaced.

try instead -

 line = line.replace("?", "-");