how to replace parameter value into the txt file?

Question

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.

Possible duplicate of Find and replace words/lines in a file — azurefrog
– azurefrog, Commented Jan 14, 2016 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
– Peter Lawrey, Commented Jan 14, 2016 at 18:38
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
– FredK, Commented Jan 14, 2016 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
– tnw, Commented Jan 14, 2016 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
– logger, Commented Jan 14, 2016 at 18:44

njachowski · Accepted Answer · 2016-01-14 18:43:35Z

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.

Alex · Accepted Answer · 2017-02-22 10:41:34Z

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

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