How to test if two words are anagram using a StringBuilder in java?

Question:

How to test if two words are anagram using a StringBuilder?

Code:

import java.util.Scanner;
 
public class Anagram {
 
  public static void main(String[] args) {
 
    Scanner sc = new Scanner(System.in);
    System.out.print("Enter first word: ");
    String word1 = sc.nextLine();
    System.out.print("Enter second word: ");
    String word2 = sc.nextLine();
 
    System.out.println("Anagram: " + isAnagram(word1,word2));
 
   }
 
 
  // Test if two words are Anagram using StringBuilder
  public static boolean isAnagram(String word1, String word2) {
 
    word1 = word1.toLowerCase();
    word2 = word2.toLowerCase();
 
    char[] characters = word1.toCharArray();
    StringBuilder sb = new StringBuilder(word2);
    for (char ch : characters) {
      int index = sb.indexOf("" + ch);
      if (index != -1) {
         sb.deleteCharAt(index);
      } else {
         return false;
      }
    }
    return sb.length() == 0 ? true : false;
  }
}

Output:

$ java Anagram
Enter first word: Star
Enter second word: rats
Anagram: true

$ java Anagram
Enter first word: rate
Enter second word: tree
Anagram: false