@NullUnmarked
public class DoubleUtilsTest extends TestCase {
  @AndroidIncompatible // no FpUtils and no Math.nextDown in old versions
  public void testNextDown() throws Exception {
    Method jdkNextDown = getJdkNextDown();
    for (double d : FINITE_DOUBLE_CANDIDATES) {
      assertEquals(jdkNextDown.invoke(null, d), DoubleUtils.nextDown(d));
    }
  }

  private static Method getJdkNextDown() throws Exception {
    try {

            ? roundArbitrarily
            : DoubleUtils.nextDown(roundArbitrarily);
      case CEILING:
        return (cmpXToRoundArbitrarily <= 0) ? roundArbitrarily : Math.nextUp(roundArbitrarily);
      case DOWN:
        if (sign(x) >= 0) {
          return (cmpXToRoundArbitrarily >= 0)
              ? roundArbitrarily
              : DoubleUtils.nextDown(roundArbitrarily);
        } else {

        .setExpectation(DoubleUtils.nextDown(-Math.pow(2, 54)), FLOOR, UP)
        .roundUnnecessaryShouldThrow()
        .test();
  }

  public void testRoundToDouble_negativeTwoToThe54MinusThree() {
    new RoundToDoubleTester(BigDecimal.valueOf((-1L << 54) - 3))
        .setExpectation(-Math.pow(2, 54), DOWN, CEILING)
        .setExpectation(

    new RoundToDoubleTester(BigInteger.valueOf((-1L << 53) - 1))
        .setExpectation(-Math.pow(2, 53), DOWN, CEILING, HALF_DOWN, HALF_EVEN)
        .setExpectation(DoubleUtils.nextDown(-Math.pow(2, 53)), FLOOR, UP, HALF_UP)
        .roundUnnecessaryShouldThrow()
        .test();
  }

  @J2ktIncompatible
  @GwtIncompatible
  public void testRoundToDouble_negativeTwoToThe54MinusOne() {

import java.math.BigInteger;

/**
 * Utilities for {@code double} primitives.
 *
 * @author Louis Wasserman
 */
@GwtIncompatible
final class DoubleUtils {
  private DoubleUtils() {}

  static double nextDown(double d) {
    return -Math.nextUp(-d);
  }

  // The mask for the significand, according to the {@link
  // Double#doubleToRawLongBits(double)} spec.
  static final long SIGNIFICAND_MASK = 0x000fffffffffffffL;

import java.math.BigInteger;

/**
 * Utilities for {@code double} primitives.
 *
 * @author Louis Wasserman
 */
@GwtIncompatible
final class DoubleUtils {
  private DoubleUtils() {}

  static double nextDown(double d) {
    return -Math.nextUp(-d);
  }

  // The mask for the significand, according to the {@link
  // Double#doubleToRawLongBits(double)} spec.
  static final long SIGNIFICAND_MASK = 0x000fffffffffffffL;

            ? roundArbitrarily
            : DoubleUtils.nextDown(roundArbitrarily);
      case CEILING:
        return (cmpXToRoundArbitrarily <= 0) ? roundArbitrarily : Math.nextUp(roundArbitrarily);
      case DOWN:
        if (x >= 0) {
          return (cmpXToRoundArbitrarily >= 0)
              ? roundArbitrarily
              : DoubleUtils.nextDown(roundArbitrarily);
        } else {

      for (int direction : new int[] {1, -1}) {
        double d = Double.longBitsToDouble(Double.doubleToLongBits(Math.scalb(1.0, i)) + direction);
        // Math.nextUp/nextDown
        if (d != Math.rint(d)) {
          fractionalBuilder.add(d);
        }
      }
    }
    for (double d :
        Doubles.asList(
            0,
            1,
            2,

      } while (approxCmp > 0);
    } else {
      BigInteger nextPow = BigInteger.TEN.multiply(approxPow);
      int nextCmp = nextPow.compareTo(x);
      while (nextCmp <= 0) {
        approxLog10++;
        approxPow = nextPow;
        approxCmp = nextCmp;
        nextPow = BigInteger.TEN.multiply(approxPow);
        nextCmp = nextPow.compareTo(x);
      }
    }

    int floorLog = approxLog10;