private boolean isPrintableChar(char ch) {
    if (Character.isISOControl(ch)) {
      return false;
    }
    Character.UnicodeBlock block = Character.UnicodeBlock.of(ch);
    return block != null && !block.equals(Character.UnicodeBlock.SPECIALS);
  }
This generates {@link KeyPress} objects from the given input stream and offers them to the given
queue.
hbase-hbtop/src/main/java/org/apache/hadoop/hbase/hbtop/terminal/impl/KeyPressGenerator.java