In this example, let’s us see how to validate password with regular expression in Java.

Source Code

package com.beginner.examples;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class ValidatePassword {
	
	private static final String PASSWORD_PATTERN = 
            "((?=.*d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%]).{6,20})";

	public static void main(String[] args) {
		
		String testPassWord1 = "hujashdfu@H156";
		String testPassWord2 = "jisdjf";
		String testPassWord3 = "hujashdfuH156";
		
		System.out.println(validate(testPassWord1));
		System.out.println(validate(testPassWord2));
		System.out.println(validate(testPassWord3));
	}
	
	public static boolean validate(final String password){
		Pattern pattern = Pattern.compile(PASSWORD_PATTERN);
		Matcher  matcher = pattern.matcher(password);
		return matcher.matches();
	  }

}

Output:

true
false
false

References

Imported packages in Java documentation:

• Matcher
• Pattern