Java: Check whether a given string is a valid hex code or not

Last update on May 24 2025 12:58:54 (UTC/GMT +8 hours)

26. Validate Hex Code

Write a Java program to check whether a given string is valid hex code or not.

A hexadecimal color value is a six-digit code preceded by a # sign, and is exactly 6 characters in length. Each character must be an alphabetic character from A-F (uppercase or lowercase.) or a digit from 0-9.

Sample Solution:

Java Code:

public class test {
 
   public static void main(String[] args) {	   
	    String text = "123456";
		System.out.println("Original String: "+text);
		System.out.println("Check the said string is a valid hex code or not? "+validate(text));
		text = "#eaecff";
		System.out.println("\nOriginal String: "+text);
		System.out.println("Check the said string is a valid hex code or not? "+validate(text));
		text = "#FF0000";
		System.out.println("\nOriginal String: "+text);
		System.out.println("Check the said string is a valid hex code or not? "+validate(text));
		text = "#DD5C5C";
		System.out.println("\nOriginal String: "+text);
		System.out.println("Check the said string is a valid hex code or not? "+validate(text));
		text = "#0000000";
		System.out.println("\nOriginal String: "+text);
		System.out.println("Check the said string is a valid hex code or not? "+validate(text));		
	}

   public static boolean validate(String text) {
	   return text.matches("#[0-9A-Fa-f]{6}");
   }
}

Sample Output:

Original String: 123456
Check the said string is a valid hex code or not? false

Original String: #eaecff
Check the said string is a valid hex code or not? true

Original String: #FF0000
Check the said string is a valid hex code or not? true

Original String: #DD5C5C
Check the said string is a valid hex code or not? true

Original String: #0000000
Check the said string is a valid hex code or not? false

Flowchart :

For more Practice: Solve these Related Problems:

• Write a Java program to validate that a string is a proper hex color code starting with '#' followed by six hex digits.
• Write a Java program to check if a string is a valid hex code allowing both 3-digit and 6-digit formats.
• Write a Java program to implement a method that uses regex to confirm whether a string matches a hex code pattern.
• Write a Java program to validate hex codes by checking both the string length and the permitted characters (0-9, A-F, a-f).

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