Extract data from string and reframe it into another

Question

I have got a string in below format:

String test = '11, -22|32.45, 34|32, 41|32, 12.12';

I am trying to convert it into below format:

{"a":11,"b":-22|"a":32.45,"b":34|"a":32,"b":41| "a":32,"b":12.12}

I tried using the logic by split() and then using join but couldn't achieve it and logic fails.

List<String> numVar = test.split('\\|');
String finalStr = '{';
for(String st : numVar){
finalStr += 'a:'+st.split(',')[0]+',';
finalStr += 'b:'+st.split(',')[1];
    //trying to add join by | logic here.
}
finalStr += '}';```

Answer 1

You can use String.replaceAll to match patterns

String testString = '11, -22|32.45, 34|32, 41|32, 12.12';
String resultString = '{'+testString.replaceAll('(-?[\\d+\\.]+), ?(-?[\\d+\\.]+)','"a":$1,"b":$2')+'}';
System.debug(resultString); // {"a":11,"b":-22|"a":32.45,"b":34|"a":32,"b":41|"a":32,"b":12.12}

This avoids the need to split and/or use any loops at all.

---

Edit:

For the regular expression, we have the following concepts:

• In Apex, a literal \ must be escaped, because Apex uses this as an escape character, too.
• To match a literal \ in Regex, we need to escape it: \\ (not used here).
• So, to match a literal \ in Regex/Apex, we need to write \\\\ (not used here).
• [...] specifies a character set, for which we use [0123456789\.]+, which is also simply [\d\.].
• ? means "match zero or once".
• + means "match at least once".
• (...) is a "capture group", which we can later reference as $1, $2, etc for each group from left to right.

For a more complete regular expression tutorial, consider a site like regex101.com, regular-expressions.info, etc.

Answer 2

Note that the first split on the pipe (|) is going to give you a list of strings like
['11, -22', '32.45, 34', '32, 41', '32, 12.12']

So to process this further, you'll either need to split() again, or just use replace() with a simple regex.

ex.

// Doesn't hurt to do this outside of the loop, but it also doesn't help
//List<String> parts = testStr.split('\\|');

List<String> processed = new List<String>();
for(String part :testStr.split('\\|')){
    system.debug(part); // should print things like '32.45, 34'

    // Using some simple regex with capturing groups to get the a/b part of the format
    // The $1 and $2 get replaced with the first and second capturing groups
    //   (the stuff contained inside the `()`) respectively
    // [0-9.-]+ covers integer strings, decimal strings, and negative numbers
    processed.add(part.replace('([0-9\\-.]+), ([0-9\\-.]+)', '"a":$1,"b":$2));
}

The result of that should be ['"a":11,"b":-22', "a":32.45,"b":34', '"a":32,"b":41','"a":32,"b":12.12']. The square braces just indicate that it's part of a list.

From there, it should be a simple String.join() to get the final output