builder.setUnsafeReplacement("X");
    builder.addEscape(' ', "_");
    Escaper first = builder.build();
    // Modify one of the existing mappings before creating a new escaper.
    builder.addEscape(' ', "-");
    builder.addEscape('!', "$");
    Escaper second = builder.build();
    // This should have no effect on existing escapers.
    builder.addEscape(' ', "*");

    // Test both escapers after modifying the builder.

        builder.addEscape(c, "\uFFFD");
      }
    }

    // Build the content escaper first and then add quote escaping for the
    // general escaper.
    builder.addEscape('&', "&");
    builder.addEscape('<', "&lt;");
    builder.addEscape('>', "&gt;");
    XML_CONTENT_ESCAPER = builder.build();
    builder.addEscape('\'', "&apos;");
    builder.addEscape('"', "&quot;");

     * @return the builder instance
     * @throws NullPointerException if {@code replacement} is null
     */
    @CanIgnoreReturnValue
    public Builder addEscape(char c, String replacement) {
      checkNotNull(replacement);
      // This can replace an existing character (the builder is re-usable).
      replacementMap.put(c, replacement);
      return this;
    }

@NullUnmarked
public class CharEscaperBuilderTest extends TestCase {

  public void testAddEscapes() {
    char[] cs = {'a', 'b', 'c'};
    CharEscaperBuilder builder = new CharEscaperBuilder().addEscapes(cs, "Z");
    Escaper escaper = builder.toEscaper();
    assertThat(escaper.escape("abcdef")).isEqualTo("ZZZdef");
  }

@NullUnmarked
public class CharEscaperBuilderTest extends TestCase {

  public void testAddEscapes() {
    char[] cs = {'a', 'b', 'c'};
    CharEscaperBuilder builder = new CharEscaperBuilder().addEscapes(cs, "Z");
    Escaper escaper = builder.toEscaper();
    assertThat(escaper.escape("abcdef")).isEqualTo("ZZZdef");
  }