Replacing Variables with Data in Java

Question

I am getting a String, for ex.: "The user << a1 >> is << a2 >> 50 years old."
And I also have an array with the data that needs to go in the String! For ex. a[0]= "John" ; a[1]= "30"
So, for this example, I would like to replace << a1 >> with John and << a2 >> with 30.

The only thing I was able to find was the following question: How to replace a set of tokens in a Java String?, but to be honest I did not understand anything and wasn't sure if that's what I'm really looking for.

So, is that really what I need to work with? If it is, I'll go read some tutorials.
Thanks in advance.

EDIT: NOTE: I don't have control over the String coming in though. So it will be exactly the way I typed it. All variables are in the form << a0 >> and the number of variable is unknown (there might even be 10 variables).

How do you connect a gap's name to its value? Is it simply "the first index in the value-array goes into the first gap in the input string"? — aliteralmind, Mar 08 '14 at 00:57

Ted Bigham · Answer 1 · 2014-03-08T00:39:27.990

4

String.format("The user %s is %s 50 years old.", a[0],a[1]);

If you must use <<a1>> and <<a2>> then something like this instead...

String s = "The user <<a1>> is <<a2>> years old.";
String output = s.replace("<<a1>>", a[0]).replace("<<a2>>", a[1]);

edited Mar 08 '14 at 00:39

answered Mar 08 '14 at 00:31

Ted Bigham

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this is probably what the OP actually wanted – stack smasher Mar 08 '14 at 00:32
Using regex is a cleaner solution. – AxiomaticNexus Mar 08 '14 at 00:52
+1 I like this answer too, but after reading up on Regex, I find that's what I was looking for. Thanks for your answer though. – Aftab Safdar Mar 09 '14 at 03:27

AxiomaticNexus · Accepted Answer · 2014-03-08T00:59:45.373

1

If you don't have control over the string, you can replace instances of << a# >> as follows:

String yourString = "The user << a1 >> is << a2 >> years old.";
String transformedString = yourString.replaceAll("<< a\d >>", "%s");

This will replace any instance of << a# >> with %s. That will change your "The user << a1 >> is << a2 >> years old." string to "The user %s is %s years old" which can be used with the string formatter.

Then use the string formatter as follows.

String finalString = String.format(transformedString, a);

edited Mar 08 '14 at 00:59

answered Mar 08 '14 at 00:32

AxiomaticNexus

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I don't have control over the String coming in though. So it will be exactly the way I typed it. All variables are in the form `<< a0 >>` – Aftab Safdar Mar 08 '14 at 00:35
@AftabHussain I have updated my answer once again since you don't know the number of variables. – AxiomaticNexus Mar 08 '14 at 01:01
I'm guessing 'a' in `String.format` is the array. Right? – Aftab Safdar Mar 08 '14 at 01:03
This is not as flexible as other answers because it forces <> and <> to always be in that order. If this is used for localizing text, enforcing the order is not an option. – Ted Bigham Mar 08 '14 at 23:03
+1 to you sir. Thanks for this answer, but I realized other stuff on the incoming String and after reading up on Regex, I'll go with that. – Aftab Safdar Mar 09 '14 at 03:30

jpdymond · Answer 3 · 2014-03-10T01:53:35.500

1

for(int i = 0; str.contains("<< a"+i+" >>"), i++) {
    str = str.replace("<< a"+i+" >>", a[i]);
}

edited Mar 10 '14 at 01:53

answered Mar 08 '14 at 00:42

jpdymond

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+1 for the looping version of my answer. Looks clean except it needs to be str = str.replace... – Ted Bigham Mar 08 '14 at 22:53

aliteralmind · Answer 4 · 2014-03-08T01:17:44.580

There's nothing stopping you from changing the format of your input string, before processing it further. It would give you more options.

That said, this uses a "reluctant" regex to replace all "gaps" as you require. It assumes that there's exactly one character before the index number, but the index can be multiple digits.

 import  java.util.regex.Pattern;
 import  java.util.regex.Matcher;
 /**
    <P>{@code java FillGaps}</P>
  **/
 public class FillGaps  {
    public static final void main(String[] ignored)  {

       String sRegex = "<< (.+?) >>";

       String sToSearch = "The user << a1 >> is << a2 >> years old.";
       String[] values = new String[] {"John", "30"};

       Matcher m = Pattern.compile(sRegex).matcher(sToSearch);
       StringBuffer sb = new StringBuffer();

       while(m.find())  {
          String gapName = m.group(1);
          String idxPlus1AsStr = gapName.substring(1, gapName.length());
          int arrayIdx = Integer.parseInt(idxPlus1AsStr) - 1;
          m.appendReplacement(sb, values[arrayIdx]);
       }
       m.appendTail(sb);

       System.out.println(sb);
    }
 }

Output:

[C:\java_code\]java FillGaps
The user John is 30 years old.

I had no clue what Regex was, but after reading and watching a tutorial, this is exactly what I need right now. Thanks — Aftab Safdar, Mar 09 '14 at 03:30

Replacing Variables with Data in Java

4 Answers4