java string class

OBJECTIVE

Study Java String class & Java String Buffer.

THEORY

Strings, which are widely used in Java programming, are a sequence of characters. In Java programming language, strings are objects.

Java platform provide the String class to create and manipulate strings.

Creating Strings:

Most direct way to create a string is to write:

String greeting = "Hello world!";    //aamirjamil

Whenever it encounters a string literal in your code, the compiler creates a String object with its value in this case, "Hello world!'.

As with any other object, you can create String objects by using the new keyword and a constructor. The String class has eleven constructors that allow you to provide the initial value of the string using different sources, such as an array of characters:

public class StringDemo{

   public static void main(String args[]){     //made by aamirjamil

      char[] helloArray = { 'h', 'e', 'l', 'l', 'o', '.'};

      String helloString = new String(helloArray);  

      System.out.println( helloString );

   }

}

AND THE OUTPUT WILL BE:

hello.

Note: String class is immutable, so that once it's created a String object can't be changed. If there's a necessity to make alot of modifications to Strings of characters then you should use String Buffer and String Builder Classes.              

String Methods:

Here are the list methods supported by String class:

PROGRAM 1: 

A PALINDROME is a word which has SAME SPELLING whether it is read from Left to Right or from Right to Left. Example: MOM, DAD, DEED, PEEP and NOON. Other words which are not PALINDROME are HELLO, DOOR and FEET. Write a program that can take a String as user input in Capital Letters and then Print YES as Output if the Input is a PALINDROME otherwise NO.

SOURCE CODE:

import java.util.Scanner;

public class Palindrome{  // made by aamirjmail

       public static void main (String[] args){

              Scanner input=new Scanner(System.in);

              String s1 = new String();

              String s2= new String();

              String s3= new String();

              System.out.println("Enter Your PALINDROME : ");

              s1=input.nextLine();

              for(int i=0; i<s1.length(); i++) {

                     s3 = s1.substring(((s1.length())-(i+1)),((s1.length())-i));  

                     s2 = s2+s3;

              }

              if(s1.equals(s2))

                     System.out.println("YES ITS A PALINDROME");    

              else

                     System.out.println("NO IT IS NOT A PALINDROME");   

       }

} 

OUTPUT:

PROGRAM 2: 

Write a program that extracts username & domain information from Email address.

For eg:, if the email address is "user@my.com", your program will print

User name = user              

Domain = my                             

Extension = com 

SOURCE CODE:

import java.util.Scanner;

public class email {   //by aamirjamil

      public static void main(String[] args) {

            Scanner enter = new Scanner(System.in);

            String email = new String();

            email = enter.nextLine();

            String uname, ext, dom;

            uname = email.substring(0,(email.indexOf('@')));

            System.out.print("Username : "+uname);

            dom = email.substring((email.indexOf('@')+1),(email.indexOf('.')));

            System.out.print("\nDomain : "+dom);

            ext = email.substring((email.indexOf('.')+1),email.length());

            System.out.print("\nExtension : "+ext);

      }

}

OUTPUT: