anyone provide good youtube channels so that i can solve questions like these how the guys came to know about sc.hasnext thing i saw it for the first time

public static void main(String[] args) {

   Scanner sc = new Scanner(System.in);

   int lineNum = 1;//How many sentences will be write

   while(sc.hasNext()==true){ // has next is boolean for loop you need true value
      String s = sc.nextLine(); //Reads the next line of input and assigns it to variable s 
      System.out.println(lineNum+" "+s); // print format
      lineNum++; // increase line number for next iteration
   }


}

}

import java.io.; import java.util.; import java.text.; import java.math.; import java.util.regex.*;

public class Solution {

public static void main(String[] args) { Scanner sc = new Scanner(System.in);

    int numberline = 1;
    String n = null;
    while (sc.hasNextLine()) {
        n = sc.nextLine();
        System.out.println(numberline + " " + n);

        numberline++;


    }
}

}

import java.util.Scanner; public class Solution {

public static void main(String[] args) {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT. Your class should be named Solution. */
    Scanner sc = new Scanner(System.in);
    int i = 1;
    while(sc.hasNextLine()){
         String st = sc.nextLine();

         System.out.println(i+" "+st);
         i++;

    }


            //this shit works all conditions passed 


}

}