JavaAlgorithms/Others/RemoveDuplicateFromString.java

package Others;

import java.io.BufferedReader;
import java.io.InputStreamReader;

/** @author Varun Upadhyay (https://github.com/varunu28) */
public class RemoveDuplicateFromString {
  public static void main(String[] args) throws Exception {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String inpStr = br.readLine();

    System.out.println("Actual string is: " + inpStr);
    System.out.println("String after removing duplicates: " + removeDuplicate(inpStr));

    br.close();
  }

  /**
   * This method produces a string after removing all the duplicate characters from input string and
   * returns it Example: Input String - "aabbbccccddddd" Output String - "abcd"
   *
   * @param s String from which duplicate characters have to be removed
   * @return string with only unique characters
   */
  public static String removeDuplicate(String s) {
    if (s == null || s.isEmpty()) {
      return s;
    }

    StringBuilder sb = new StringBuilder();
    int n = s.length();

    for (int i = 0; i < n; i++) {
      if (sb.toString().indexOf(s.charAt(i)) == -1) {
        sb.append(String.valueOf(s.charAt(i)));
      }
    }

    return sb.toString();
  }
}