How to do string concatenation in Scala

Question

I have the following code that based on the input (args) I want to create a string but the answer is incorrect. I have args(0) is a path, args(1) is an operand like "+", and args(2) is a number (and I want to put space between them:

 //some code .. var Statement="" for (j<-0 to 2) { if (Files.exists(Paths.get(args(j)))){ Statement.concat(inputXml) Statement.concat(" ") } else{ Statement.concat(args(j)) Statement.concat(" ") } println(args(j)) println(Statement) } println(Statement) //some code ...

the output is a blank! I have used this link as reference. Would you please help me on this I am new in Scala. Thanks.

also: a.concat(b) should be written as a+b

dhg
– dhg

2015-05-28 19:43:33 +00:00
Commented May 28, 2015 at 19:43 — dhg
– dhg, Commented May 28, 2015 at 19:43

Karl · Accepted Answer · 2015-05-28 19:39:16Z

String.concat returns an entirely new String object. It will not mutate your current Statement variable at all. Now I wouldn't recommend you do the following, but all you technically need to change is reassign Statement to the return value of all your concat calls:

 //some code .. var Statement="" for (j<-0 to 2) { if (Files.exists(Paths.get(args(j)))){ Statement = Statement.concat(inputXml) Statement = Statement.concat(" ") } else{ Statement = Statement.concat(args(j)) Statement = Statement.concat(" ") } println(args(j)) println(Statement) } println(Statement) //some code ...

A more performant solution would be to use a StringBuilder instead.

val Statement = StringBuilder.newBuilder Statement.append(...) println(Statement.toString)

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