Java Obtain the first 100 characters of a string

import java.io.*;

public class First100Chars {
   /**
   * This method Obtain the first 100 characters of a string.
   * @param str String to obtain the first 100 characters.
   * @return String Obtains the first 100 characters of a string.
   */   
   public String first100Chars(String str) {
       //Variable to store the first 100 characters
       String first100 = "";
       //Obtain the first 100 characters of the string
       first100 = str.substring(0, 100);
       //Return the first 100 characters of the string
       return first100;
   }

   /**
   * One Example
   */
   public static void main(String args[]) throws IOException {

      First100Chars  first100Chars= new First100Chars ();
      //Example
      String str = "This is a string";
      String first100 = first100Chars.first100Chars(str);
      //Output
      System.out.println("First 100 characters of the string is :" + first100); //This is a string
   }
}