Password Authentication

password.java

import java.net.PasswordAuthentication;

public class password {
    public static void main(String[] args) {
        String pass="Sagar@123aaa";
        boolean flag0=false;
        boolean flag1=false;
        boolean flag2=false;
        boolean flag3=false;
        int a=pass.length();

        for (int i=0;i<pass.length();i++){

            int b=pass.charAt(i);

            if (b>=65&&b<=97){
                flag0=true;
            }
            else if (b>=97&&b<=122){
                flag1 = true;
            }

            else if (b>=33&&b<=47||b>=91&&b<=96||b>=58&&b<=64||b>=123&&b<=126){
                flag2= true;
            }
            else if (b>=48&&b<=57){
                flag3=true;
            } else{
                System.out.println("PASSWORD INVALID");

            }

        }
        if (flag0==true&&flag1==true&&flag2==true&&flag3==true&&a>=8&&a<=12){
            System.out.println("VALID PASSWORD!");

        }else{
            System.out.println("INVALID PASSWORD!");
        }

    }
}