Control keyboard input in Java

Question

I have this program to write and have no idea how to control keyboard input:

Write a method to check whether the word entered is valid or not. Valid word should:

1. Have at least 10 characters
2. Start with a letter
3. Contain a letter in upper case
4. Contain at least 3 digits
5. Contain a special character (e.g. @,$.% …etc)
6. Contain a space

Answer 1

You don't need to validate it on every key stroke, wait till the user has entered the word, then validate. Assuming you are using console input:

System.out.print("Enter something > ");
Scanner input = new Scanner(System.in);

String inputString = input.nextLine();

//perform validations on inputString, heres the first one:
//regex could be used instead of multiple if statements
if(inputString.length() < 10) {
    System.out.println("Validation failed, word was too short");
}
else if ... 

Answer 2

You can use this regular expression:

String REGEX = "(^[a-zA-Z](?=.*\\d{3,})(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%])(?=\\s+).{10,})";
String INPUT = "your password";
Pattern pattern = Pattern.compile(REGEX);
Matcher matcher = pattern.matcher(INPUT);
System.out.println("matches(): "+matcher.matches());


^[a-zA-Z]           # Start with a letter
(?=.*\\d{3,})       # at least three digits must occur
(?=.*[a-z])         # a lower case letter must occur at least once
(?=.*[A-Z])         # an upper case letter must occur at least once
(?=.*[@#$%])        # a special character must occur at least once
(?=\\s+)            # a space must occur at least once
.{10,}              # anything, at least ten places though
$                   # end-of-string

To use this, read your password (from file,swing elements,...) and call a method, say validate(String pass), inside validate check it against the regex.

Answer 3

Scanner input=new Scanner(System.in);
System.out.print("Enter Number");

//in here "input" is a Scanner name you can use any name for it as OBAMA.

int x=input.nextInt();

//here you can assigne the key board value for "x".

System.out.println(x);

then you can print it.