Java RegEx – find words by length example shows how to find words by their length (words of a specific or certain length) in a sting using Java regular expression pattern.
How to find words in a Java string by length using a regex pattern?
In order to find words of a specific length, we need to combine two regex expressions. The first one is the word boundary i.e. “\b”. The word boundary “\b”, as the name suggests, matches with any word boundary, for example, at the start or at the end of the string.
Along with that, we also need a pattern repetition expression that is created using curly braces. Please see the below-given table to understand how that works.
|
1 2 3 |
{n} - The previous pattern should match exactly n times {n, } - The previous pattern should match minimum n times {n, m} - The previous pattern should match minimum n times and maximum m times |
We are going to use the first one in our regex pattern as we need to find the word of a certain length. When we combine these two together, our pattern looks like given below.
|
1 |
\\b\\w{5}\\b |
The whole pattern means a word boundary, followed by any word character 5 times, followed by a word boundary. In this example, we are going to find words of length 5.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 |
package com.javacodeexamples.regex; import java.util.regex.Matcher; import java.util.regex.Pattern; public class RegExWordByLength { public static void main(String[] args) { String str = "one two three four five six seven eight"; //create a pattern & a matcher Pattern pattern = Pattern.compile("(\\b\\w{5}\\b)"); Matcher matcher = pattern.matcher(str); while( matcher.find() ) { System.out.println(matcher.group(1)); } } } |
Output
|
1 2 3 |
three seven eight |
You can replace 5 with whatever word length you are looking for. For example, to find a word having the length of 4, the pattern would be “(\\b\\w{4}\\b)”.
The good thing about this pattern is it also works with numbers. See below given example, where I want to find all the numbers having the length of 3 in the string.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 |
package com.javacodeexamples.regex; import java.util.regex.Matcher; import java.util.regex.Pattern; public class RegExWordByLength { public static void main(String[] args) { String str = "1 22 333 4444 55555 666"; Pattern pattern = Pattern.compile("(\\b\\w{3}\\b)"); Matcher matcher = pattern.matcher(str); while( matcher.find() ) { System.out.println(matcher.group(1)); } } } |
Output
|
1 2 |
333 666 |
If you want to find all the words having a minimum length of 2 and a maximum length of 4, the regex pattern will be “(\\b\\w{2,4}\\b)”.
|
1 2 3 4 5 6 7 8 |
String str = "1 22 333 4444 55555 666"; Pattern pattern = Pattern.compile("(\\b\\w{2,4}\\b)"); Matcher matcher = pattern.matcher(str); while( matcher.find() ) { System.out.println(matcher.group(1)); } |
Output
|
1 2 3 4 |
22 333 4444 666 |
As you can see from the output, it found words of length 2, 3, and 4. Similarly, if you want to find all the words having a minimum length of 3 and no maximum limit, you can use the below-given code.
|
1 2 3 4 5 6 7 8 |
String str = "1 22 333 4444 55555 666"; Pattern pattern = Pattern.compile("(\\b\\w{3,}\\b)"); Matcher matcher = pattern.matcher(str); while( matcher.find() ) { System.out.println(matcher.group(1)); } |
Output
|
1 2 3 4 |
333 4444 55555 666 |
As you can see from the output, it found all the words having lengths of more than 3.
If you want to learn more about regular expressions, please visit the Java regex tutorial.
Please let me know your views in the comments section below.
About the author
- Gson – Serialize HashMap null entries - April 5, 2023
- Gson: Convert String to JsonObject without POJO - April 5, 2023
- Gson – Convert JSON to a Typed ArrayList - April 5, 2023
