How to validate Time in 24 Hours format with regular expression

Time in 24-Hour Format Regular Expression Pattern

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

Description

(				#start of group #1
 [01]?[0-9]			#  start with 0-9,1-9,00-09,10-19
 |				#  or
 2[0-3]				#  start with 20-23
)				#end of group #1
 :				#    follow by a semi colon (:)
  [0-5][0-9]			#      follw by 0..5 and 0..9, which means 00 to 59

The 24-hour clock format is start from 0-23 or 00-23 then a semi colon (:) and follow by 00-59.

Java Regular Expression Example

package com.mkyong.regex;

import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class Time24HoursValidator{
	
	  private Pattern pattern;
	  private Matcher matcher;
 
	  private static final String TIME24HOURS_PATTERN = 
                 "([01]?[0-9]|2[0-3]):[0-5][0-9]";
	  
	  public Time24HoursValidator(){
		  pattern = Pattern.compile(TIME24HOURS_PATTERN);
	  }
	  
	  /**
	   * Validate time in 24 hours format with regular expression
	   * @param time time address for validation
	   * @return true valid time fromat, false invalid time format
	   */
	  public boolean validate(final String time){
		  
		  matcher = pattern.matcher(time);
		  return matcher.matches();
	    	    
	  }
}

Time format that match:

1. “01:00”, “02:00”, “13:00”,
2. “1:00”, “2:00”, “13:01”,
3. “23:59″,”15:00”
4. “00:00″,”0:00”

Time format doesn’t match:

1. “24:00” – hour is out of range [0-23]
2. “12:60” – minute is out of range [00-59]
3. “0:0” – invalid format for minute, at least 2 digits
4. “13:1” – invalid format for minute, at least 2 digits
5. “101:00” – hour is out of range [0-23]

Unit Test – Time24HoursValidatorTest

package com.mkyong.regex;

import org.testng.Assert;
import org.testng.annotations.*;
 
/**
 * Time 24 hours format validator Testing
 * @author mkyong
 *
 */
public class Time24HoursValidatorTest {
 
	private Time24HoursValidator time24HoursValidator;
    
	@BeforeClass
        public void initData(){
		time24HoursValidator = new Time24HoursValidator();
        }
	
	@DataProvider
	public Object[][] ValidTime24HoursProvider() {
		return new Object[][]{
			new Object[] {"01:00"}, new Object[] {"02:00"},
                        new Object[] {"13:00"}, new Object[] {"1:00"}, 
                        new Object[] {"2:00"},new Object[] {"13:01"},
		        new Object[] {"23:59"}, new Object[] {"15:00"},
		        new Object[] {"00:00"}, new Object[] {"0:00"}
		};
	}	
	
	@DataProvider
	public Object[][] InvalidTime24HoursProvider() {
		return new Object[][]{
			new Object[] {"24:00"},new Object[] {"12:60"},
			new Object[] {"0:0"},new Object[] {"13:1"},
			new Object[] {"101:00"}
		};
	}

	@Test(dataProvider = "ValidTime24HoursProvider")
	public void ValidTime24HoursTest(String time) {
	    boolean valid = time24HoursValidator.validate(time);
	    System.out.println("Time24Hours is valid : " + time + " , " + valid);
	    Assert.assertEquals(true, valid);
	}
	
	@Test(dataProvider = "InvalidTime24HoursProvider", 
                 dependsOnMethods="ValidTime24HoursTest")
	public void InValidTime24HoursTest(String time) {
	    boolean valid = time24HoursValidator.validate(time);
	    System.out.println("Time24Hours is valid : " + time + " , " + valid);
	    Assert.assertEquals(false, valid); 
	}	
}

Unit Test – Result

Time24Hours is valid : 01:00 , true
Time24Hours is valid : 02:00 , true
Time24Hours is valid : 13:00 , true
Time24Hours is valid : 1:00 , true
Time24Hours is valid : 2:00 , true
Time24Hours is valid : 13:01 , true
Time24Hours is valid : 23:59 , true
Time24Hours is valid : 15:00 , true
Time24Hours is valid : 00:00 , true
Time24Hours is valid : 0:00 , true
Time24Hours is valid : 24:00 , false
Time24Hours is valid : 12:60 , false
Time24Hours is valid : 0:0 , false
Time24Hours is valid : 13:1 , false
Time24Hours is valid : 101:00 , false
PASSED: ValidTime24HoursTest("01:00")
PASSED: ValidTime24HoursTest("02:00")
PASSED: ValidTime24HoursTest("13:00")
PASSED: ValidTime24HoursTest("1:00")
PASSED: ValidTime24HoursTest("2:00")
PASSED: ValidTime24HoursTest("13:01")
PASSED: ValidTime24HoursTest("23:59")
PASSED: ValidTime24HoursTest("15:00")
PASSED: ValidTime24HoursTest("00:00")
PASSED: ValidTime24HoursTest("0:00")
PASSED: InValidTime24HoursTest("24:00")
PASSED: InValidTime24HoursTest("12:60")
PASSED: InValidTime24HoursTest("0:0")
PASSED: InValidTime24HoursTest("13:1")
PASSED: InValidTime24HoursTest("101:00")

===============================================
    com.mkyong.regex.Time24HoursValidatorTest
    Tests run: 15, Failures: 0, Skips: 0
===============================================


===============================================
mkyong
Total tests run: 15, Failures: 0, Skips: 0
===============================================

Reference

http://en.wikipedia.org/wiki/24-hour_clock

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