Checking letter case (Upper/Lower) within a string in Java
The problem that I am having is that I can't get my Password Verification Program to check a string to ensure that, 1 of the characters is in upper case and one is in lower case, it will check the whole string for one of the other and print the error message based on which statement it is checking.
I have looked over this site and the internet for an answer and I am unable to find one. This is homework.
Below is my current code.
import java.util.Scanner;
public class password
{
public static void main(String[] args)
{
Scanner stdIn = new Scanner(System.in);
String password;
String cont = "y";
char ch;
boolean upper = false;
boolean lower = false;
System.out.println("Setting up your password is easy. To view requirements enter Help.");
System.out.print("Enter password or help: ");
password = stdIn.next();
ch = password.charAt(0);
while (cont.equalsIgnoreCase("y"))
{
while (password.isEmpty())
{
System.out.print("Enter password or help: ");
password = stdIn.next();
}
if (password.equalsIgnoreCase("help"))
{
System.out.println("Password must meet these requirements." +
"\nMust contain 8 characters.\nMust contain 1 lower case letter." +
"\nMust contain 1 upper case letter.\nMust contain 1 numeric digit." +
"\nMust contain 1 special character !@#$%^&*\nDoes not contain the word AND or NOT.");
password = "";
}
else if (password.length() < 8)
{
System.out.println("Invalid password - Must contain 8 charaters.");
password = "";
}
else if (!(Character.isLowerCase(ch)))
{
for (int i=1; i<password.length(); i++)
{
ch = password.charAt(i);
if (!Character.isLowerCase(ch))
{
System.out.println("Invalid password - Must have a Lower Case character.");
password = "";
}
}
}
else if (!(Character.isUpperCase(ch)))
{
for (int i=0; i<password.length(); i++)
{
ch = password.charAt(i);
if (!Character.isUpperCase(ch))
{
System.out.println("Invalid password - Must have an Upper Case character.");
password = "";
}
}
}
else
{
System.out.println("Your password is " + password);
System.out.print("Would you like to change your password? Y/N: ");
cont = stdIn.next();
password = "";
}
while (!cont.equalsIgnoreCase("y") && !cont.equalsIgnoreCase("n"))
{
System.out.print("Invalid Answer. Please enter Y or N: ");
cont = stdIn.next();
}
}
}
}
Solution 1:
To determine if a String contains an upper case and a lower case char, you can use the following:
boolean hasUppercase = !password.equals(password.toLowerCase());
boolean hasLowercase = !password.equals(password.toUpperCase());
This allows you to check:
if(!hasUppercase)System.out.println("Must have an uppercase Character");
if(!hasLowercase)System.out.println("Must have a lowercase Character");
Essentially, this works by checking if the String is equal to its entirely lowercase, or uppercase equivalent. If this is not true, then there must be at least one character that is uppercase or lowercase.
As for your other conditions, these can be satisfied in a similar way:
boolean isAtLeast8 = password.length() >= 8;//Checks for at least 8 characters
boolean hasSpecial = !password.matches("[A-Za-z0-9 ]*");//Checks at least one char is not alpha numeric
boolean noConditions = !(password.contains("AND") || password.contains("NOT"));//Check that it doesn't contain AND or NOT
With suitable error messages as above.
Solution 2:
A loop like this one:
else if (!(Character.isLowerCase(ch)))
{
for (int i=1; i<password.length(); i++)
{
ch = password.charAt(i);
if (!Character.isLowerCase(ch))
{
System.out.println("Invalid password - Must have a Lower Case character.");
password = "";
}
// end if
} //end for
}
Has an obvious logical flaw: You enter it if the first character is not lowercase, then test if the second character is not lower case. At that point you throw an error.
Instead, you should do something like this (not full code, just an example):
boolean hasLower = false, hasUpper = false, hasNumber = false, hasSpecial = false; // etc - all the rules
for ( ii = 0; ii < password.length(); ii++ ) {
ch = password.charAt(ii);
// check each rule in turn, with code like this:
if Character.isLowerCase(ch) hasLower = true;
if Character.isUpperCase(ch) hasUpper = true;
// ... etc for all the tests you want to do
}
if(hasLower && hasUpper && ...) {
// password is good
}
else {
// password is bad
}
Of course the code snippet you provided, besides the faulty logic, did not have code to test for the other conditions that your "help" option printed out. As was pointed out in one of the other answers, you could consider using regular expressions to help you speed up the process of finding each of these things. For example,
hasNumber : use regex pattern "\d+" for "find at least one digit"
hasSpecial : use regex pattern "[!@#$%^&*]+" for "find at least one of these characters"
In code:
hasNumber = password.matches(".*\\d.*"); // "a digit with anything before or after"
hasSpecial = password.matches(".*[!@#$%^&*].*");
hasNoNOT = !password.matches(".*NOT.*");
hasNoAND = !password.matches(".*AND.*");
It is possible to combine these things in clever ways - but especially when you are a novice regex user, it is much better to be a little bit "slow and tedious", and get code that works first time (plus you will be able to figure out what you did six months from now).