integer.java

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  public int intValue()
  {
    return value;
  }

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

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

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

  /**
   * Converts the <code>Integer</code> value to a <code>String</code> and
   * assumes a radix of 10.
   *
   * @return the <code>String</code> representation
   */
  public String toString()
  {
    return String.valueOf(value);
  }

  /**
   * Return a hashcode representing this Object. <code>Integer</code>'s hash
   * code is simply its value.
   *
   * @return this Object's hash code
   */
  public int hashCode()
  {
    return value;
  }

  /**
   * Returns <code>true</code> if <code>obj</code> is an instance of
   * <code>Integer</code> and represents the same int value.
   *
   * @param obj the object to compare
   * @return whether these Objects are semantically equal
   */
  public boolean equals(Object obj)
  {
    return obj instanceof Integer && value == ((Integer) obj).value;
  }

  /**
   * Get the specified system property as an <code>Integer</code>. The
   * <code>decode()</code> method will be used to interpret the value of
   * the property.
   *
   * @param nm the name of the system property
   * @return the system property as an <code>Integer</code>, or null if the
   *         property is not found or cannot be decoded
   * @throws SecurityException if accessing the system property is forbidden
   * @see System#getProperty(String)
   * @see #decode(String)
   */
  public static Integer getInteger(String nm)
  {
    return getInteger(nm, null);
  }

  /**
   * Get the specified system property as an <code>Integer</code>, or use a
   * default <code>int</code> value if the property is not found or is not
   * decodable. The <code>decode()</code> method will be used to interpret
   * the value of the property.
   *
   * @param nm the name of the system property
   * @param val the default value
   * @return the value of the system property, or the default
   * @throws SecurityException if accessing the system property is forbidden
   * @see System#getProperty(String)
   * @see #decode(String)
   */
  public static Integer getInteger(String nm, int val)
  {
    Integer result = getInteger(nm, null);
    return result == null ? new Integer(val) : result;
  }

  /**
   * Get the specified system property as an <code>Integer</code>, or use a
   * default <code>Integer</code> value if the property is not found or is
   * not decodable. The <code>decode()</code> method will be used to
   * interpret the value of the property.
   *
   * @param nm the name of the system property
   * @param val the default value
   * @return the value of the system property, or the default
   * @throws SecurityException if accessing the system property is forbidden
   * @see System#getProperty(String)
   * @see #decode(String)
   */
  public static Integer getInteger(String nm, Integer def)
  {
    if (nm == null || "".equals(nm))
      return def;
    nm = System.getProperty(nm);
    if (nm == null)
      return def;
    try
      {
        return decode(nm);
      }
    catch (NumberFormatException e)
      {
        return def;
      }
  }

  /**
   * Convert the specified <code>String</code> into an <code>Integer</code>.
   * The <code>String</code> may represent decimal, hexadecimal, or
   * octal numbers.
   *
   * <p>The extended BNF grammar is as follows:<br>
   * <pre>
   * <em>DecodableString</em>:
   *      ( [ <code>-</code> ] <em>DecimalNumber</em> )
   *    | ( [ <code>-</code> ] ( <code>0x</code> | <code>0X</code>
   *              | <code>#</code> ) <em>HexDigit</em> { <em>HexDigit</em> } )
   *    | ( [ <code>-</code> ] <code>0</code> { <em>OctalDigit</em> } )
   * <em>DecimalNumber</em>:
   *        <em>DecimalDigit except '0'</em> { <em>DecimalDigit</em> }
   * <em>DecimalDigit</em>:
   *        <em>Character.digit(d, 10) has value 0 to 9</em>
   * <em>OctalDigit</em>:
   *        <em>Character.digit(d, 8) has value 0 to 7</em>
   * <em>DecimalDigit</em>:
   *        <em>Character.digit(d, 16) has value 0 to 15</em>
   * </pre>
   * Finally, the value must be in the range <code>MIN_VALUE</code> to
   * <code>MAX_VALUE</code>, or an exception is thrown.
   *
   * @param s the <code>String</code> to interpret
   * @return the value of the String as an <code>Integer</code>
   * @throws NumberFormatException if <code>s</code> cannot be parsed as a
   *         <code>int</code>
   * @throws NullPointerException if <code>s</code> is null
   * @since 1.2
   */
  public static Integer decode(String str)
  {
    return new Integer(parseInt(str, 10, true));
  }

  /**
   * Compare two Integers numerically by comparing their <code>int</code>
   * values. The result is positive if the first is greater, negative if the
   * second is greater, and 0 if the two are equal.
   *
   * @param i the Integer to compare
   * @return the comparison
   * @since 1.2
   */
  public int compareTo(Integer i)
  {
    if (value == i.value)
      return 0;
    // Returns just -1 or 1 on inequality; doing math might overflow.
    return value > i.value ? 1 : -1;
  }

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

  /**
   * Helper for converting unsigned numbers to String.
   *
   * @param num the number
   * @param exp log2(digit) (ie. 1, 3, or 4 for binary, oct, hex)
   */
  // Package visible for use by Long.
  static String toUnsignedString(int num, int exp)
  {
    // Use an array large enough for a binary number.
    int mask = (1 << exp) - 1;
    char[] buffer = new char[32];
    int i = 32;
    do
      {
        buffer[--i] = digits[num & mask];
        num >>>= exp;
      }
    while (num != 0);

    // Package constructor avoids an array copy.
    return new String(buffer, i, 32 - i, true);
  }

  /**
   * Helper for parsing ints, used by Integer, Short, and Byte.
   *
   * @param str the string to parse
   * @param radix the radix to use, must be 10 if decode is true
   * @param decode if called from decode
   * @return the parsed int value
   * @throws NumberFormatException if there is an error
   * @throws NullPointerException if decode is true and str if null
   * @see #parseInt(String, int)
   * @see #decode(String)
   * @see Byte#parseInt(String, int)
   * @see Short#parseInt(String, int)
   */
  static int parseInt(String str, int radix, boolean decode)
  {
    if (! decode && str == null)
      throw new NumberFormatException();
    int index = 0;
    int len = str.length();
    boolean isNeg = false;
    if (len == 0)
      throw new NumberFormatException();
    int ch = str.charAt(index);
    if (ch == '-')
      {
        if (len == 1)
          throw new NumberFormatException();
        isNeg = true;
        ch = str.charAt(++index);
      }
    if (decode)
      {
        if (ch == '0')
          {
            if (++index == len)
              return 0;
            if ((str.charAt(index) & ~('x' ^ 'X')) == 'X')
              {
                radix = 16;
                index++;
              }
            else
              radix = 8;
          }
        else if (ch == '#')
          {
            radix = 16;
            index++;
          }
      }
    if (index == len)
      throw new NumberFormatException();

    int max = MAX_VALUE / radix;
    // We can't directly write `max = (MAX_VALUE + 1) / radix'.
    // So instead we fake it.
    if (isNeg && MAX_VALUE % radix == radix - 1)
      ++max;

    int val = 0;
    while (index < len)
      {
	if (val < 0 || val > max)
	  throw new NumberFormatException();

        ch = Character.digit(str.charAt(index++), radix);
        val = val * radix + ch;
        if (ch < 0 || (val < 0 && (! isNeg || val != MIN_VALUE)))
          throw new NumberFormatException();
      }
    return isNeg ? -val : val;
  }
}