Method precomputedInternal

output/java_guava/1.4.19/CharMatcher.java:563–588

This is the actual implementation of #precomputed, but we bounce calls through a method on Platform so that we can have different behavior in GWT. This implementation tries to be smart in a number of ways. It recognizes cases where the negation is cheaper to precompute than the m

()

   */

  @GwtIncompatible // java.util.BitSet
  CharMatcher precomputedInternal() {
    final BitSet table = new BitSet();
    setBits(table);
    int totalCharacters = table.cardinality();
    if (totalCharacters * 2 <= DISTINCT_CHARS) {
      return precomputedPositive(totalCharacters, table, toString());
    }
    else {
      // TODO(lowasser): is it worth it to worry about the last character of large matchers?
      table.flip(Character.MIN_VALUE, Character.MAX_VALUE + 1);
      int negatedCharacters = DISTINCT_CHARS - totalCharacters;
      String suffix = ".negate()";
      final String description = toString();
      String negatedDescription =
        description.endsWith(suffix)
          ? description.substring(0, description.length() - suffix.length())
          : description + suffix;
      return new NegatedFastMatcher(precomputedPositive(negatedCharacters, table, negatedDescription)) {
        @Override
        public String toString() {
          return description;
        }
      };
    }
  }

  /**
   * Helper method for {@link #precomputedInternal} that doesn't test if the negation is cheaper.