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java regex pattern validate 24 hours format


Regular expressions

Regular expressions represents a sequence of symbols and characters expressing a string or pattern to be searched for within a longer piece of text. The abbreviation for regular expression is regex. In programming regular expressions are mainly used to define constraint on strings like password, email validation.

([01]?[0-9]|2[0-3]):[0-5][0-9]

This regular expression refers to a pattern which start from 0-23 or 00-23 then a semi colon (:) and follow by 00-59.

Example

package com.tutorialspointexamples;
 
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class RegexTest {
	private static final String PATTERN = 
			"([01]?[0-9]|2[0-3]):[0-5][0-9]";
	public static void main(String args[]){ 
		List<String> values = new ArrayList<String>();	
		values.add("05:00"); 
		values.add("17:01"); 
		values.add("24:00");
		values.add("13:1");
 
		Pattern pattern = Pattern.compile(PATTERN);
		for (String value : values){
		  Matcher matcher = pattern.matcher(value);
		  if(matcher.matches()){
			  System.out.println("Time "+ value +" is valid 24Hours Format");
		  }else{
			  System.out.println("Time "+ value +" is invalid 24Hours Format");
		  }		  
		}
	}
}

Output

Time 05:00 is valid 24Hours Format
Time 17:01 is valid 24Hours Format
Time 24:00 is invalid 24Hours Format
Time 13:1 is invalid 24Hours Format
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