*   <li>{@link CharMatcher#ascii} matches ASCII characters and provides text processing methods
 *       which operate only on the ASCII characters of a string.
 * </ul>
 *
 * @author Catherine Berry
 * @author Gregory Kick
 * @since 7.0
 */
@GwtCompatible
public final class Ascii {

  private Ascii() {}

  /* The ASCII control characters, per RFC 20. */
  /**

zhenghua <******@****.***> 1492724018 -0700

    assertEquals(LOWER, Ascii.toLowerCase(UPPER));
    assertSame(LOWER, Ascii.toLowerCase(LOWER));
    assertEquals(IGNORED, Ascii.toLowerCase(IGNORED));
    assertEquals("foobar", Ascii.toLowerCase("fOobaR"));
  }

  public void testToUpperCase() {
    assertEquals(UPPER, Ascii.toUpperCase(LOWER));
    assertSame(UPPER, Ascii.toUpperCase(UPPER));
    assertEquals(IGNORED, Ascii.toUpperCase(IGNORED));

    assertEquals(LOWER, Ascii.toLowerCase(UPPER));
    assertSame(LOWER, Ascii.toLowerCase(LOWER));
    assertEquals(IGNORED, Ascii.toLowerCase(IGNORED));
    assertEquals("foobar", Ascii.toLowerCase("fOobaR"));
  }

  public void testToUpperCase() {
    assertEquals(UPPER, Ascii.toUpperCase(LOWER));
    assertSame(UPPER, Ascii.toUpperCase(UPPER));
    assertEquals(IGNORED, Ascii.toUpperCase(IGNORED));

    assertEquals(ASCII, Files.toString(temp, UTF_8));
  }

  public void testCopyIdenticalFiles() throws IOException {
    File temp1 = createTempFile();
    Files.write(ASCII, temp1, UTF_8);
    File temp2 = createTempFile();
    Files.write(ASCII, temp2, UTF_8);
    Files.copy(temp1, temp2);
    assertEquals(ASCII, Files.toString(temp2, UTF_8));
  }

  public void testEqual() throws IOException {

    return NONALPHA.charAt(random.nextInt(NONALPHA.length()));
  }

  @Benchmark
  int asciiStringToUpperCase(int reps) {
    String string = noWorkToDo ? Ascii.toUpperCase(testString) : testString;

    int dummy = 0;
    for (int i = 0; i < reps; i++) {
      dummy += Ascii.toUpperCase(string).length();
    }
    return dummy;
  }

  @Benchmark
  int asciiCharSequenceToUpperCase(int reps) {

    @Override
    String normalizeWord(String word) {
      return Ascii.toUpperCase(word);
    }

    @Override
    String convert(CaseFormat format, String s) {
      if (format == LOWER_HYPHEN) {
        return Ascii.toLowerCase(s.replace('_', '-'));
      }
      if (format == LOWER_UNDERSCORE) {
        return Ascii.toLowerCase(s);
      }
      return super.convert(format, s);
    }
  };

    @Override
    String normalizeWord(String word) {
      return Ascii.toUpperCase(word);
    }

    @Override
    String convert(CaseFormat format, String s) {
      if (format == LOWER_HYPHEN) {
        return Ascii.toLowerCase(s.replace('_', '-'));
      }
      if (format == LOWER_UNDERSCORE) {
        return Ascii.toLowerCase(s);
      }
      return super.convert(format, s);
    }
  };

  @BeforeExperiment
  public void setUp() {
    // precalculate some random strings of ascii characters.
    StringBuilder sb = new StringBuilder();
    Random random = new Random(0xdeadbeef); // for unpredictable but reproducible behavior
    sb.ensureCapacity(size);
    for (int k = 0; k < size; k++) {
      // [9-127) includes all ascii non-control characters
      sb.append((char) (random.nextInt(127 - 9) + 9));
    }

    StringBuilder builder = new StringBuilder();
    long copied =
        CharStreams.copy(
            wrapAsGenericReadable(new StringReader(ASCII)), wrapAsGenericAppendable(builder));
    assertEquals(ASCII, builder.toString());
    assertEquals(ASCII.length(), copied);

    StringBuilder builder2 = new StringBuilder();
    copied =
        CharStreams.copy(