float.java

gcc的组建

   *
   * @param v the <code>float</code> to compare
   * @return whether the argument is <code>NaN</code>
   */
  public static boolean isNaN(float v)
  {
    // This works since NaN != NaN is the only reflexive inequality
    // comparison which returns true.
    return v != v;
  }

  /**
   * Return <code>true</code> if the <code>float</code> has a value
   * equal to either <code>NEGATIVE_INFINITY</code> or
   * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
   *
   * @param v the <code>float</code> to compare
   * @return whether the argument is (-/+) infinity
   */
  public static boolean isInfinite(float v)
  {
    return v == POSITIVE_INFINITY || v == NEGATIVE_INFINITY;
  }

  /**
   * Return <code>true</code> if the value of this <code>Float</code>
   * is the same as <code>NaN</code>, otherwise return <code>false</code>.
   *
   * @return whether this <code>Float</code> is <code>NaN</code>
   */
  public boolean isNaN()
  {
    return isNaN(value);
  }

  /**
   * Return <code>true</code> if the value of this <code>Float</code>
   * is the same as <code>NEGATIVE_INFINITY</code> or
   * <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
   *
   * @return whether this <code>Float</code> is (-/+) infinity
   */
  public boolean isInfinite()
  {
    return isInfinite(value);
  }

  /**
   * Convert the <code>float</code> value of this <code>Float</code>
   * to a <code>String</code>.  This method calls
   * <code>Float.toString(float)</code> to do its dirty work.
   *
   * @return the <code>String</code> representation
   * @see #toString(float)
   */
  public String toString()
  {
    return toString(value);
  }

  /**
   * Return the value of this <code>Float</code> as a <code>byte</code>.
   *
   * @return the byte value
   * @since 1.1
   */
  public byte byteValue()
  {
    return (byte) value;
  }

  /**
   * Return the value of this <code>Float</code> as a <code>short</code>.
   *
   * @return the short value
   * @since 1.1
   */
  public short shortValue()
  {
    return (short) value;
  }

  /**
   * Return the value of this <code>Integer</code> as an <code>int</code>.
   *
   * @return the int value
   */
  public int intValue()
  {
    return (int) value;
  }

  /**
   * Return the value of this <code>Integer</code> as a <code>long</code>.
   *
   * @return the long value
   */
  public long longValue()
  {
    return (long) value;
  }

  /**
   * Return the value of this <code>Float</code>.
   *
   * @return the float value
   */
  public float floatValue()
  {
    return value;
  }

  /**
   * Return the value of this <code>Float</code> as a <code>double</code>
   *
   * @return the double value
   */
  public double doubleValue()
  {
    return value;
  }

  /**
   * Return a hashcode representing this Object. <code>Float</code>'s hash
   * code is calculated by calling <code>floatToIntBits(floatValue())</code>.
   *
   * @return this Object's hash code
   * @see #floatToIntBits(float)
   */
  public int hashCode()
  {
    return floatToIntBits(value);
  }

  /**
   * Returns <code>true</code> if <code>obj</code> is an instance of
   * <code>Float</code> and represents the same float value. Unlike comparing
   * two floats with <code>==</code>, this treats two instances of
   * <code>Float.NaN</code> as equal, but treats <code>0.0</code> and
   * <code>-0.0</code> as unequal.
   *
   * <p>Note that <code>f1.equals(f2)</code> is identical to
   * <code>floatToIntBits(f1.floatValue()) ==
   *    floatToIntBits(f2.floatValue())</code>.
   *
   * @param obj the object to compare
   * @return whether the objects are semantically equal
   */
  public boolean equals(Object obj)
  {
    if (! (obj instanceof Float))
      return false;

    float f = ((Float) obj).value;

    // Avoid call to native method. However, some implementations, like gcj,
    // are better off using floatToIntBits(value) == floatToIntBits(f).
    // Check common case first, then check NaN and 0.
    if (value == f)
      return (value != 0) || (1 / value == 1 / f);
    return isNaN(value) && isNaN(f);
  }

  /**
   * Convert the float to the IEEE 754 floating-point "single format" bit
   * layout. Bit 31 (the most significant) is the sign bit, bits 30-23
   * (masked by 0x7f800000) represent the exponent, and bits 22-0
   * (masked by 0x007fffff) are the mantissa. This function collapses all
   * versions of NaN to 0x7fc00000. The result of this function can be used
   * as the argument to <code>Float.intBitsToFloat(int)</code> to obtain the
   * original <code>float</code> value.
   *
   * @param value the <code>float</code> to convert
   * @return the bits of the <code>float</code>
   * @see #intBitsToFloat(int)
   */
  // GCJ LOCAL: We diverge from Classpath for efficiency.
  public static native int floatToIntBits(float value);
  // END GCJ LOCAL

  /**
   * Convert the float to the IEEE 754 floating-point "single format" bit
   * layout. Bit 31 (the most significant) is the sign bit, bits 30-23
   * (masked by 0x7f800000) represent the exponent, and bits 22-0
   * (masked by 0x007fffff) are the mantissa. This function leaves NaN alone,
   * rather than collapsing to a canonical value. The result of this function
   * can be used as the argument to <code>Float.intBitsToFloat(int)</code> to
   * obtain the original <code>float</code> value.
   *
   * @param value the <code>float</code> to convert
   * @return the bits of the <code>float</code>
   * @see #intBitsToFloat(int)
   */
  // GCJ LOCAL: We diverge from Classpath for efficiency.
  public static native int floatToRawIntBits(float value);
  // END GCJ LOCAL

  /**
   * Convert the argument in IEEE 754 floating-point "single format" bit
   * layout to the corresponding float. Bit 31 (the most significant) is the
   * sign bit, bits 30-23 (masked by 0x7f800000) represent the exponent, and
   * bits 22-0 (masked by 0x007fffff) are the mantissa. This function leaves
   * NaN alone, so that you can recover the bit pattern with
   * <code>Float.floatToRawIntBits(float)</code>.
   *
   * @param bits the bits to convert
   * @return the <code>float</code> represented by the bits
   * @see #floatToIntBits(float)
   * @see #floatToRawIntBits(float)
   */
  // GCJ LOCAL: We diverge from Classpath for efficiency.
  public static native float intBitsToFloat(int bits);
  // END GCJ LOCAL

  /**
   * Compare two Floats numerically by comparing their <code>float</code>
   * values. The result is positive if the first is greater, negative if the
   * second is greater, and 0 if the two are equal. However, this special
   * cases NaN and signed zero as follows: NaN is considered greater than
   * all other floats, including <code>POSITIVE_INFINITY</code>, and positive
   * zero is considered greater than negative zero.
   *
   * @param f the Float to compare
   * @return the comparison
   * @since 1.2
   */
  public int compareTo(Float f)
  {
    return compare(value, f.value);
  }

  /**
   * Behaves like <code>compareTo(Float)</code> unless the Object
   * is not an <code>Float</code>.
   *
   * @param o the object to compare
   * @return the comparison
   * @throws ClassCastException if the argument is not a <code>Float</code>
   * @see #compareTo(Float)
   * @see Comparable
   * @since 1.2
   */
  public int compareTo(Object o)
  {
    return compare(value, ((Float) o).value);
  }

  /**
   * Behaves like <code>new Float(x).compareTo(new Float(y))</code>; in
   * other words this compares two floats, special casing NaN and zero,
   * without the overhead of objects.
   *
   * @param x the first float to compare
   * @param y the second float to compare
   * @return the comparison
   * @since 1.4
   */
  public static int compare(float x, float y)
  {
    if (isNaN(x))
      return isNaN(y) ? 0 : 1;
    if (isNaN(y))
      return -1;
    // recall that 0.0 == -0.0, so we convert to infinities and try again
    if (x == 0 && y == 0)
      return (int) (1 / x - 1 / y);
    if (x == y)
      return 0;

    return x > y ? 1 : -1;
  }
}