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Can someone explain me how to replace value in .txt file. For example I've got a 'Test.txt' file with a line:

 1,23343,EUR,1.45,${param1},Mr,${param2}

and I've got a HashMap like this one below:

Map map= new HashMap();
    map.put("param1", "1000");
    map.put("param2", "4000");

So now I would like to use the key value of my HashMap and pass it to the .txt file but I have no idea how to do this.

My file Test.txt should look like

1,23343,EUR,1.45,1000,Mr,4000

Please, help me. Thank you in advance.

EdXX
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  • Possible duplicate of [Find and replace words/lines in a file](http://stackoverflow.com/questions/3935791/find-and-replace-words-lines-in-a-file) – azurefrog Jan 14 '16 at 18:35
  • Your file need to be in memory as text and then you can apply a replaceAll on the text. A file is just bytes on a disk, you can't pass anything to it. – Peter Lawrey Jan 14 '16 at 18:38
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    It is not clear what you mean by "pass it to the .txt file". Do you want to write to the file? Do you want to read a particular line from the file, that matches your key? – FredK Jan 14 '16 at 18:39
  • I *think* you're asking how to replace `param1` with `1000` and `param2` with `4000`. What have you tried so far? Look into how to read, parse, and write lines in a text file. This is basic stuff. – tnw Jan 14 '16 at 18:41
  • this isn't javascript / jsp file you dont need ${param1} and you cannot pass it to a text file. you can just create a buffer reader. read from the file, and write values using basic String manipulation tricks – logger Jan 14 '16 at 18:44

2 Answers2

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You could do this on the command line with the envsubst command. 

export param1=1000
export param2=4000

envsubst < original.txt > new.txt

envsubst is a standard command line utility in many linux distros.

njachowski
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https://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/text/StrSubstitutor.html

Example:

 Map map = HashMap();
 map.put("param1", "1000");
 map.put("param2", "4000");
 StrSubstitutor sub = new StrSubstitutor(map);
 String resolvedString = sub.replace("1,23343,EUR,1.45,${param1},Mr,${param2}");

yielding:

1,23343,EUR,1.45,1000,Mr,4000

Alex
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