去除重复字符

import java.util.*;


public class Solution {
  /**
   * 
   * @param str string字符串 
   * @return string字符串
   */
  public String removeDuplicatedChars (String str) {
    StringBuilder ansBuilder = new StringBuilder();
    boolean[] flags = new boolean[128];
    for (int i = 0, n = str.length(); i < n; i++) {
      char c = str.charAt(i);
      if (!flags[c]) {
        ansBuilder.append(c);
        flags[c] = true;
      }
    }
    return ansBuilder.toString();
  }
}