In java language,
How to use the regular expression to deal with the string
$.store.book[Random(1,9)].title
and replace the part of Random(1,9) to a real random number between 1 to 9?
So basically, the result string will like $.store.book[3].title or $.store.book[5].title
Anybody who can help me?
The easiest way I can think of would be using String.replace():
String str = "$.store.book[Random(1,9)].title";
str = str.replace("Random(1,9)", String.valueOf((int)(Math.random() * 9 + 1)));
System.out.println(str);
Sample output being:
$.store.book[7].title
Using a regular expression to capture arbitrary numbers would be (see online demo here):
String input= "$.store.book[Random(1,9)].title";
System.out.println("Input: "+ input);
Pattern p = Pattern.compile("(?<=\\[)Random\\((\\d+),(\\d+)\\)(?=\\])");
Matcher m = p.matcher(input);
String output = input;
if(m.find()) {
int min = Integer.valueOf(m.group(1));
int max = Integer.valueOf(m.group(2));
int rand = min + (int)(Math.random() * ((max - min) + 1));
output = output.substring(0, m.start()) + rand + output.substring(m.end());
}
System.out.println("Output: "+ output );
Example output:
Input: $.store.book[Random(1,9)].title
Output: $.store.book[6].title
Online demo for code below.
public static String replaceRandom(String input) {
Pattern p = Pattern.compile("(?<=\\[)Random\\((\\d+),(\\d+)\\)(?=\\])");
Matcher m = p.matcher(input);
String output = input;
if (m.find()) {
int min = Integer.valueOf(m.group(1));
int max = Integer.valueOf(m.group(2));
int rand = min + (int)(Math.random() * ((max - min) + 1));
output = output.substring(0, m.start()) +rand+ output.substring(m.end());
}
return output;
}
public static void main(String[] args) {
System.out.println("(1,9): "
+ replaceRandom("$.store.book[Random(1,9)].title"));
System.out.println("(1,999): "
+ replaceRandom("$.store.book[Random(1,999)].title"));
System.out.println("(50,200): "
+ replaceRandom("$.store.book[Random(50,200)].title"));
}
Example output:
(1,9): $.store.book[4].title
(1,999): $.store.book[247].title
(50,200): $.store.book[71].title
You will have to do this in three steps.
First you will have to find the "Random(1,9)" string. You can use a regular expression with capture groups to parse out the value range. See http://docs.oracle.com/javase/tutorial/essential/regex/groups.html.
Next you will have to generate your random number.
Finally you can use String.replaceFirst to replace the string with the number you've generated.
If you want to support multiple occurrences per string, repeat that until there are none left.
Edit: That said, if your range is always 1 to 9, Jlewis071's answer is sufficient and straightforward.
Random rnd = new Random(System.currentTimeMillis())
Pattern pattern = Pattern.compile(".*Random\\((\\d+),(\\d+)\\).*");
Matcher matcher = pattern.matcher(str);
while (matcher.find()) {
int min = matcher.group(1);
int max = matcher.group(2);
int newInt = rnd.nextInt(max-min+1) + min;
str = str.replaceFirst("Random\\([^)]+\\)",String.valueOf(newInt));
matcher = pattern.matcher(str);
}
And I probably messed up the regexes... and I see acdcjunior just posted it all, complete with an online IDE to verify it. So I'll post my answer anyway so people appreciate my effort! But his answer is error free for sure, and along the same lines :) Then again, mine does repeat the replacement throughout the entire string, as suggested by other answers.
Try using String.replace();
Example to suit your requirement:
String data = "$.store.book[Random(1,9)].title";
Random random = new Random();
// Replace the sub-string
String replacedData = data.replace("Random(1,9)", String.valueOf(random.nextInt() / 10000));
System.out.println(replacedData); // after replacement
