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Character Class in Java (Part 2)

>

The Character Class: (Part 1)

Methods of Character class:


  • Example: Method -> isDigit() [validating name]
    // Using isDigit() to check whether name or any string entered by user has a digit or not.
    import java.util.Scanner;
    class test {
    public static void main(String ar[]) {
    Scanner sc=new Scanner(System.in);
    boolean flag =false; // keep the switch/flag off in the beginning.
    System.out.println("Enter name:");
    String name = sc.nextLine();
    // extract each character from name by charAt() method.
    for(int i=0;i<name.length();i++)
    {
    char ch = name.charAt(i); // get the 0th character, 1st character and so on..
    // if ch is a digit, its invalid for name.
    if(Character.isDigit(ch))
    {
    flag=true; // if the digit is found, set flag to true.
    System.out.println("NAME CANNOT CONTAIN DIGITS.. ");// no need to check rest of characters now. so break the loop.
    break;
    }
    }
    if(flag==false) // if flag was still holding old value (false), then the string/name is valid.
    {
    System.out.println("VALID NAME!!");
    }
    }
    }
    view raw test.java hosted with ❤ by GitHub
  • Example: Method -> isLetter() [validating mobile number]
    // Using isLetter() to check whether contact number or any integer input entered by user has a letter or not.
    import java.util.Scanner;
    class test {
    public static void main(String ar[]) {
    Scanner sc=new Scanner(System.in);
    boolean flag =false; // keep the switch/flag off in the beginning.
    System.out.println("Enter phone number:");
    String number = sc.nextLine();
    if(number.length()==10){
    // extract each character from number by charAt() method.
    for(int i=0;i<number.length();i++)
    {
    char ch = number.charAt(i); // get the 0th character, 1st character and so on..
    // if ch is a letter, its invalid for contact number.
    if(Character.isLetter(ch))
    {
    flag=true; // if a letter is found, set flag to true.
    System.out.println("MOBILE NUMBER CANNOT CONTAIN LETTERS.. ");// no need to check rest of characters now. so break the loop.
    break;
    }
    }
    if(flag==false) {// if flag was still holding old value (false), then the contact-number is valid.
    System.out.println("VALID MOBILE NUMBER!!");
    }
    }
    else
    {
    System.out.println("INVALID LENGTH MOBILE NUMBER!!");
    }
    }
    }
    /* OUTPUT:
    Enter phone number:
    123
    INVALID LENGTH MOBILE NUMBER!!
    Enter phone number:
    121313DS
    INVALID LENGTH MOBILE NUMBER!!
    Enter phone number:
    123456789P
    MOBILE NUMBER CANNOT CONTAIN LETTERS..
    Enter phone number:
    1234567890
    VALID MOBILE NUMBER!!
    */
    view raw test.java hosted with ❤ by GitHub
  • Example: Method -> isLetterOrDigit() [validating user_id / username]
    // Using isLetterOrDigit() to check whether user_id or any string entered by user has a digit and/or letter and no other symbols or characters.
    import java.util.Scanner;
    class test {
    public static void main(String ar[]) {
    Scanner sc=new Scanner(System.in);
    boolean flag =false; // keep the switch/flag off in the beginning.
    System.out.println("Enter user_id:");
    String user_id = sc.nextLine();
    // extract each character from user_id by charAt() method.
    for(int i=0;i<user_id.length();i++)
    {
    char ch = user_id.charAt(i); // get the 0th character, 1st character and so on..
    // if ch is a letter and/or digit, its valid for user_id. If not, its invalid.
    if(! Character.isLetterOrDigit(ch)) // using ! to check the invlaid condition.
    {
    flag=true; // if any special symbol is found, set flag to true.
    System.out.println("USER ID CAN ONLY CONTAIN LETTERS AND DIGITS.. ");// no need to check rest of characters now. so break the loop.
    break;
    }
    }
    if(flag==false) {// if flag was still holding old value (false), then the user_id is valid.
    System.out.println("VALID USER ID!!");
    }
    }
    }
    /* OUTPUT
    Enter user_id:
    user_1
    USER ID CAN ONLY CONTAIN LETTERS AND DIGITS..
    Enter user_id:
    user@123
    USER ID CAN ONLY CONTAIN LETTERS AND DIGITS..
    Enter user_id:
    user1
    VALID USER ID!!
    */
    view raw test.java hosted with ❤ by GitHub
  • Example: Method -> isLowerCase()
    // Using isLowerCase() to check whether name or any string entered by user is lowercase.
    import java.util.Scanner;
    class test {
    public static void main(String ar[]) {
    Scanner sc=new Scanner(System.in);
    System.out.println("Enter any string:");
    String name = sc.nextLine();
    // extract each character from user_id by charAt() method.
    for(int i=0;i<name.length();i++)
    {
    char ch = name.charAt(i); // get the 0th character, 1st character and so on..
    // if ch is a lowercase character or not
    if(Character.isLowerCase(ch))
    {
    System.out.println("Lowercase character: "+ ch);
    }
    else
    {
    System.out.println("Non-Lowercase character: "+ ch);
    }
    }
    }
    }
    /* OUTPUT:
    Enter any string:
    hEllo!
    Lowercase character: h
    Non-Lowercase character: E
    Lowercase character: l
    Lowercase character: l
    Lowercase character: o
    Non-Lowercase character: !
    */
    view raw test.java hosted with ❤ by GitHub
  • Example: Method -> isUpperCase()
    // Using isUpperCase() to check whether name or any string entered by user is uppercase or not.
    import java.util.Scanner;
    class test
    {
    public static void main(String ar[])
    {
    Scanner sc=new Scanner(System.in);
    System.out.println("Enter any string:");
    String name = sc.nextLine();
    // extract each character from name by charAt() method.
    for(int i=0;i<name.length();i++)
    {
    char ch = name.charAt(i); // get the 0th character, 1st character and so on..
    // if ch is a uppercase character or not
    if(Character.isUpperCase(ch))
    {
    System.out.println("Uppercase character: "+ ch);
    }
    else
    {
    System.out.println("Non-Uppercase character: "+ ch);
    }
    }
    }
    }
    /* OUTPUT:
    Enter any string:
    JaVA
    Uppercase character: J
    Non-Uppercase character: a
    Uppercase character: V
    Uppercase character: A
    */
    view raw test.java hosted with ❤ by GitHub
  • Example: Method -> toUpperCase() and toLowerCase()
    // Convert uppercase to lowercase and vice-versa.
    import java.util.Scanner;
    class test {
    public static void main(String ar[]) {
    Scanner sc=new Scanner(System.in);
    System.out.println("Enter any string:");
    String name = sc.nextLine();
    String ans="";
    // extract each character from user_id by charAt() method.
    for(int i=0;i<name.length();i++)
    {
    char ch = name.charAt(i); // get the 0th character, 1st character and so on..
    if(Character.isUpperCase(ch)) // if character is uppercase, convert to lowercase and append in the final ans.
    {
    ans = ans + Character.toLowerCase(ch);
    }
    else
    {
    ans = ans + Character.toUpperCase(ch); // vice-versa
    }
    }
    System.out.println("Converted String: "+ans);
    }
    }
    /* OUTPUT:
    Enter any string:
    Java Programming
    Converted String: jAVA pROGRAMMING
    */
    view raw test.java hosted with ❤ by GitHub
Click HERE for the list of Methods of Character class.
Click HERE for the ASCII Table for different Characters

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