Using Regular Expression in Java to extract information from a String

Question

I have one input String like this:

"I am Duc/N Ta/N Van/N" 

String "/N" present it is the Name of one person.
The expected output is:

Name: Duc Ta Van

How can I do it by using regular expression?

Answer 1

Here is the regex to use to capture every "name" preceded by a /N

(\w+)\/N

Validate with Regex101

Now, you just need to loop on every match in that String and concatenate the to get the result :

String pattern = "(\\w+)\\/N";
String test = "I am Duc/N Ta/N Van/N";
Matcher m = Pattern.compile(pattern).matcher(test);

StringBuilder sbNames = new StringBuilder(); 
while(m.find()){
    sbNames.append(m.group(1)).append(" ");
}
System.out.println(sbNames.toString());

Duc Ta Van

It is giving you the hardest part. I let you adapt this to match your need.

Note :
In java, it is not required to escape a forward slash, but to use the same regex in the entire answer, I will keep "(\\w+)\\/N", but "(\\w+)/N" will work as well.

Answer 2

You can use Pattern and Matcher like this :

String input = "I am Duc/N Ta/N Van/N";
Pattern pattern = Pattern.compile("([^\\s]+)/N");
Matcher matcher = pattern.matcher(input);
String result = "";
while (matcher.find()) {
    result+= matcher.group(1) + " ";
}

System.out.println("Name: " + result.trim());

Output

Name: Duc Ta Van

---

Another Solution using Java 9+

From Java9+ you can use Matcher::results like this :

String input = "I am Duc/N Ta/N Van/N";
String regex = "([^\\s]+)/N";
Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(input);
String result = matcher.results().map(s -> s.group(1)).collect(Collectors.joining(" "));

System.out.println("Name: " + result); // Name: Duc Ta Van

Answer 3

I've used "[/N]+" as the regular expression.

Regex101

[] = Matches characters inside the set

\/ = Matches the character / literally (case sensitive)

+ = Matches between one and unlimited times, as many times as possible, giving back as needed (greedy)