Checking letter case Upper Lower within a string in Java

Question

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        amp   nDoes not contain the word AND or NOT                      password                                 else if  password length    lt  8                                System out println  Invalid password - Must contain 8 charaters                     password                                 else if    Character isLowerCase ch                                  for  int i 1  i lt 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 lt 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    amp  amp   cont equalsIgnoreCase  n                                  System out print  Invalid Answer  Please enter Y or N                      cont   stdIn next

User · Answer

This is quite old and  SinkingPoint already gave a great answer above  Now  with functional idioms available in Java 8 we could give it one more twist  You would have two lambdas   Function lt String  Boolean gt  hasLowerCase   s - gt  s chars   filter c - gt  Character isLowerCase c   count    gt  0  Function lt String  Boolean gt  hasUpperCase   s - gt  s chars   filter c - gt  Character isUpperCase c   count    gt  0    Then in code we could check password rules like this   if   hasUppercase apply password   System out println  Must have an uppercase Character    if   hasLowercase apply password   System out println  Must have a lowercase Character      As to the other checks   Function lt String Boolean gt  isAtLeast8   s - gt  s length    gt   8    Checks for at least 8 characters Function lt String Boolean gt  hasSpecial     s - gt   s matches   A-Za-z0-9        Checks at least one char is not alpha numeric Function lt String Boolean gt  noConditions   s - gt    s contains  AND      s contains  NOT      Check that it doesn t contain AND or NOT   In some cases  it is arguable  whether creating the lambda adds value in terms of communicating intent  but the good thing about lambdas is that they are functional

User · Answer

That s what I got       Scanner scanner   new Scanner System in       System out println  Please enter a nickname         while   scanner hasNext   a-zA-Z  3 8                System out println  Nickname should contain only Alphabetic letters  At least 3 and max 8 letters            scanner next              String nickname   scanner next        System out println  Thank you  Got     nickname     Read about regex Pattern here  https   docs oracle com javase 7 docs api java util regex Pattern html

User · Answer

A loop like this one   else if    Character isLowerCase ch                                  for  int i 1  i lt 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  lt  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  amp  amp  hasUpper  amp  amp              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          amp      for  find at least one of these characters    In code   hasNumber    password matches      d           a digit with anything before or after  hasSpecial   password matches            amp         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

User · Answer

I have streamlined the answer of  Quirliom above into functions that can be used   private static boolean hasLength CharSequence data        if  String valueOf data  length    gt   8  return true      else return false     private static boolean hasSymbol CharSequence data        String password   String valueOf data       boolean hasSpecial    password matches   A-Za-z0-9           return hasSpecial     private static boolean hasUpperCase CharSequence data        String password   String valueOf data       boolean hasUppercase    password equals password toLowerCase         return hasUppercase     private static boolean hasLowerCase CharSequence data        String password   String valueOf data       boolean hasLowercase    password equals password toUpperCase         return hasLowercase

User · Answer

package passwordValidator   import java util Scanner   public class Main                   author felipe mello               private static Scanner scanner   new Scanner System in                   Create a password validator from an input string  via TDD        The validator should return true if         The Password is at least 8 characters long         The Password contains uppercase Letters atLeastOne          The Password contains digits at least one          The Password contains symbols at least one                public static void main String   args            System out println  Please enter a password            String password   scanner nextLine                checkPassword password                                 param checkPassword the method check password is validating the input from the the user and check if it matches the password requirements         return             public static boolean checkPassword String password           boolean upperCase    password equals password toLowerCase       check if the input has a lower case letter         boolean lowerCase    password equals password toUpperCase       check if the input has a CAPITAL case letter         boolean isAtLeast8   password length   gt  8                       check if the input is greater than 8 characters         boolean hasSpecial    password matches   A-Za-z0-9               check if the input has a special characters         boolean hasNumber    password matches      d                    check if the input contains a digit         if  isAtLeast8               System out println  Your Password is not big enough n please enter a password with minimun of 8 characters                return true           else if  upperCase               System out println  Password must contain at least one UPPERCASE letter                return true           else if  lowerCase               System out println  Password must contain at least one lower case letter                return true           else if  hasSpecial               System out println  Password must contain a special character                return true           else if hasNumber               System out println  Password must contain at least one number                return true           else              System out println  Your password    password    sucessfully match the requirements                return true

User · Answer

function TellFirstCharacterType inputString       var firstCharacter   inputString 0       if isNaN firstCharacter            if firstCharacter    firstCharacter toUpperCase                 return  It s a uppercase character                     else              return  It s a lowercase character                       else          return  It s a Number

User · Answer

A quick look through the documentation on regular expression sytanx should bring up ways to tell if it contains a lower upper case character at some point

User · Answer

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    gt   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

User · Answer

Although this code is likely beyond the understanding of a novice  it can be done in one line using a regex with positive and negative look-aheads   boolean ok        password matches         A-Z               amp           d       AND NOT     a-z

[java] Checking letter case (Upper/Lower) within a string in Java

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