indexOf():
==========
Note:
=====
1) indexOf() method can use to search not only the character it can also search about the string.
and can retur: the first occurrence value.

class IndexOfMethod{
    public static void main(String x[])
    {
        String s1 = "Java Programming langauge is hig-level and Object-Oriented Programming Language";
        
        System.out.println(s1.indexOf('a'));
        System.out.println(s1.indexOf("Program"));
        System.out.println(s1.indexOf("a"));
    }
} 

2) indexOf() can return: "-1"
	when we can search about unknown element (character/string) in the given string.

class IndexOfMethod{
    public static void main(String x[])
    {
        String s1 = "Java Programming langauge is hig-level and Object-Oriented Programming Language";
        
        System.out.println(s1.indexOf('A'));
    }
}

lastIndexOf():
=============
Note:
====
1) lastIndexOf() can also use to search about the string in the given string.

class IndexOfMethod{
    public static void main(String x[])
    {
        String s1 = "Java Programming Language is hig-level and Object-Oriented Programming Language";
        
        System.out.println(s1.lastIndexOf('l'));
        System.out.println(s1.lastIndexOf("Language"));
    }
}

2) lastIndexOf() can return '-1'
	when the searching object is unknown to the given string.

class IndexOfMethod{
    public static void main(String x[])
    {
        String s1 = "Java Programming Language is hig-level and Object-Oriented Programming Language";
        
       System.out.println(s1.lastIndexOf('A'));
    }
}

============================
# If we are searching about "empty string" in the given string:
================================================================
output : 0

class IndexOfMethod{
    public static void main(String x[])
    {
        String s1 = "Java Programming Language is hig-level and Object-Oriented Programming Language";
        
       System.out.println(s1.indexOf(""));
    }
}

==============================
output: Last Character Index

class IndexOfMethod{
    public static void main(String x[])
    {
        String s1 = "Java Programming Language is hig-level and Object-Oriented Programming Language";
        
       System.out.println(s1.lastIndexOf(""));
       System.out.println(s1.length());
    }
}

======================================================
# If we are searching about null value in the given string:
===========================================================
indexOf():
==========
	Null Pointer Exception

class IndexOfMethod{
    public static void main(String x[])
    {
        String s1 = "Java Programming Language is hig-level and Object-Oriented Programming Language";
        
       System.out.println(s1.indexOf(null));
    }
}
=====================
lastIndexOf():
==============
	Null Pointer Exception

class IndexOfMethod{
    public static void main(String x[])
    {
        String s1 = "Java Programming Language is hig-level and Object-Oriented Programming Language";
        
       System.out.println(s1.lastIndexOf(null));
    }
}
===========================================
startsWith():
=============
Syntax:
	str-obj.startsWith("searching-object")

==> return : boolean value (true/false)
==> can use to check whether the given string has begin with given group of characters (string) ot not.

Url: https://www.ashokit.in

// WAP TO CHECK WHETHER THE GIVEN URL IS VALID OR NOT.
import java.util.Scanner;

class URLValidation{
    public static void main(String[] args)
    {
        Scanner sco = new Scanner(System.in);
        
        System.out.println("Enter the URL:");
        String URL = sco.nextLine();
        
        if((URL.startsWith("https://www.")) || (URL.startsWith("http://www.")))
        {
            System.out.println("The Given URL is Valid URL");
        }
        else
        {
            System.out.println("The Given URL is Invalid URL");
        }
    }
}

========================================
endsWith():
==========
Syntax:
	str-object.endsWith("Searching-object")

returns: Boolean Values (true/false)

to check wheter the given string ending with specified group of characters (string) or not.

Ex: "abcd@gmail.com" or "abcd@rediffmail.com" etc.

// WAP TO CHECK WHETHER THE GIVEN MAIL ID IS VALID OR INVALID

import java.util.Scanner;

class Mailvalidator{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);
        
        System.out.println("Enter the user mail id:");
        String mail = scan.next();
        
        if((mail.endsWith("@gmail.com")))
        {
            System.out.println("The Given Mail Id is Valid Mail Id.");
        }
        else
        {
            System.out.println("The Given Mail Id is Invalid mail Id.");
        }
    }
}
==============================================
trim():
=======
"   ravi kumar     "
trim() ==> "ravi kumar"

==> use to trim the blank spaces from the beginning of string and/or from the ending of the string.
Syntax:
	String-object.trim()

class TrimmingoBlankSpaces{
    public static void main(String[] args)
    {
        String s1 = "Hello World!";
        String s2 = "   Hello Java";
        String s3 = "Hi all      ";
        String s4 = "   Java Programs     ";
        
        System.out.println(s1);
        System.out.println(s2);
        System.out.println(s3);
        System.out.println(s4);
        System.out.println();
        
        System.out.println(s1.trim());
        System.out.println(s2.trim());
        System.out.println(s3.trim());
        System.out.println(s4.trim());
    }
}
==========================================
toCharArray():
=============
"hello"
{'h','e','l','l','o'}

==> use to convert a string into a character array.
Syntax:
	str-obj.toCharArray();

class StringToCharacterArray{
    public static void main(String[] args)
    {
        String s = "Hello World!";
        
        System.out.println(s);
        
        char[] ar = s.toCharArray();
        
        // for(char c : s)
        // {
        //     System.out.println(c);
        // }
        
        for(char c:ar)
        {
            System.out.println(c);
        }
    }
}
===========================================
Conversion of Primitive Datatype to String:
==========================================
valueOf():
==========
Syntax:
	String.valueOf(primitive Data variable)

class PrimitiveToString{
    public static void main(String[] args)
    {
        int a = 112;
        float b = 1.12F;
        boolean c = true;
        
        String s1 = String.valueOf(a);
        String s2 = String.valueOf(b);
        String s3 = String.valueOf(c);
        
        System.out.println("s1 = "+s1);
        System.out.println("s2 = "+s2);
        System.out.println("s3 = "+s3);
    }
}

============================================
String Concatenation:
=====================
Joining of two strings into one string is called as "String Concatenation".
Symbol: '+'

Syntax:
	Str3 = str1 + str2

class StringConcatenation{
    public static void main(String[] args)
    {
        int a = 100;
        String s1 = "Hello";
        String s2 = "Java";
        
        String s3 = s1 + s2;
        String s4 = a + s1;
        // joining of an integer to the string
        String s5 = s4 + 123.123;
        // joining the string to the double value
      
        System.out.println(s1);
        System.out.println(s2);
        System.out.println(s3);
        System.out.println(s4);
        System.out.println(s5);
        System.out.println(s5 + true);
        // joining of string to the boolean value
    }
}