private static final int EXTENDED_ASCII_CODES = 256;
...
public static boolean isAnagram(String str1, String str2) {
  int[] chCounts = new int[EXTENDED_ASCII_CODES];
  char[] chStr1 = str1.replaceAll("\\s",
    "").toLowerCase().toCharArray();
  char[] chStr2 = str2.replaceAll("\\s",
    "").toLowerCase().toCharArray();

  if (chStr1.length != chStr2.length) {
    return false;
  }

  for (int i = 0; i < chStr1.length; i++) {
    chCounts[chStr1[i]]++;
    chCounts[chStr2[i]]--;
  }

  for (int i = 0; i < chCounts.length; i++) {
    if (chCounts[i] != 0) {
      return false;
    }
  }

  return true;
}