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// This is a sandbox to experiment with CoderPad's execution capabilities.
// It's a temporary, throw-away session only visible to you.

import java.io.*;
import java.util.*;

/*
 * To execute Java, please define "static void main" on a class
 * named Solution.
 *
 * If you need more classes, simply define them inline.
 */

class Solution {
  public static void main(String[] args) {
    Solution solution =new Solution();
    String[] input = {
          null,
          "",
          "GOOGLE"
        };
    for(int i=0;i< input.length;i++) {
      System.out.println("Input: " + input[i] +
                       ", Result: " + solution.possiblePalindromes(input[i]));
    }
  }
    
  public Set<String> possiblePalindromes(String input){
    Set<String> result = new HashSet<>();
    if(input == null || input.length() < 1) {
        return result;   
    }
    for(int i=0;i<input.length();i++){
        expand(i, i, input, result); // odd
        expand(i, i+1, input, result); // even
    }
    return result;
  }
    
  public void expand(int low, int high, String input, Set<String> result) {
      while(low >=0 && high < input.length() && 
            input.charAt(low) == input.charAt(high)){
          result.add(input.substring(low, high + 1));
          low--;
          high++;
      }
  }
}