StringBuilder sb = new StringBuilder();
for (final char character : malformedString.toCharArray()) {
  if (Character.isDefined(character)) {
    sb.append(character);
  }
}
sb.toString();

StringBuilder sb = new StringBuilder();
for (final Character character : malformedString.toCharArray()) {
  if (character != null) {
    sb.append(character);
  }
}
sb.toString();

if (character == ''){
     //
   }

for (char c : string.toCharArray()) {
    System.out.printf("U+%04x ", (int) c);
}

String sanitized = dirty.replaceAll("[uFEFF-uFFFF]", "");

final StringBuilder sb = new StringBuilder();
    for (final char character : body.toCharArray()) {
       if (character != 'uFEFF') {
          sb.append(character);
       }
     }
 final String sanitzedString = sb.toString();

public static String removeUTF8BOM(String s) {
    if (s.startsWith("uFEFF")) {
        s = s.substring(1);
    }
    return s;
}

StringBuilder sb = new StringBuilder();
    for (char character : myString.toCharArray()) {
        int i = (int) character;
        if (i > 0 && i <= 256) {
            sb.append(character);
        }
    }
    return sb.toString();

for (int i = 0; i < s.length(); i++)
    if (s.charAt(i) == ' ') {
        your code....
    }

if (character.equals(' ')){ // }