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java regex pattern validate image file extension


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.

Regular expression image file extension pattern

([^\s]+(\.(?i)(jpg|png|gif|bmp))$)

This regular expression refers to a pattern which must have 1 or more strings (but not white space), follow by dot “.” and string end in “jpg” or “png” or “gif” or “bmp”, and the file extensive is case-insensitive.

Example

package com.codesjava;
 
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 = 
			"^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$";
	public static void main(String args[]){ 
		List<String> values = new ArrayList<String>();	
		values.add("#1f1f1F"); 
		values.add("#1AFFa1"); 
		values.add("123456");
		values.add("F00");
 
		Pattern pattern = Pattern.compile(PATTERN);
		for (String value : values){
		  Matcher matcher = pattern.matcher(value);
		  if(matcher.matches()){
			  System.out.println("Color code "+ value +" is valid");
		  }else{
			  System.out.println("Color code "+ value +" is invalid");
		  }		  
		}
	}
}

Output

Color code #1f1f1F is valid
Color code #1AFFa1 is valid
Color code 123456 is invalid
Color code F00 is invalid
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