string.java

gcc的组建

  {
    return toUpperCase(Locale.getDefault());
  }

  /**
   * Trims all characters less than or equal to <code>'\u0020'</code>
   * (<code>' '</code>) from the beginning and end of this String. This
   * includes many, but not all, ASCII control characters, and all
   * {@link Character#isWhitespace(char)}.
   *
   * @return new trimmed String, or this if nothing trimmed
   */
  public String trim()
  {
    int limit = count + offset;
    if (count == 0 || (value[offset] > '\u0020'
                       && value[limit - 1] > '\u0020'))
      return this;
    int begin = offset;
    do
      if (begin == limit)
        return "";
    while (value[begin++] <= '\u0020');
    int end = limit;
    while (value[--end] <= '\u0020');
    return substring(begin - offset - 1, end - offset + 1);
  }

  /**
   * Returns this, as it is already a String!
   *
   * @return this
   */
  public String toString()
  {
    return this;
  }

  /**
   * Copies the contents of this String into a character array. Subsequent
   * changes to the array do not affect the String.
   *
   * @return character array copying the String
   */
  public char[] toCharArray()
  {
    if (count == value.length)
      return (char[]) value.clone();

    char[] copy = new char[count];
    VMSystem.arraycopy(value, offset, copy, 0, count);
    return copy;
  }

  /**
   * Returns a String representation of an Object. This is "null" if the
   * object is null, otherwise it is <code>obj.toString()</code> (which
   * can be null).
   *
   * @param obj the Object
   * @return the string conversion of obj
   */
  public static String valueOf(Object obj)
  {
    return obj == null ? "null" : obj.toString();
  }

  /**
   * Returns a String representation of a character array. Subsequent
   * changes to the array do not affect the String.
   *
   * @param data the character array
   * @return a String containing the same character sequence as data
   * @throws NullPointerException if data is null
   * @see #valueOf(char[], int, int)
   * @see #String(char[])
   */
  public static String valueOf(char[] data)
  {
    return valueOf (data, 0, data.length);
  }

  /**
   * Returns a String representing the character sequence of the char array,
   * starting at the specified offset, and copying chars up to the specified
   * count. Subsequent changes to the array do not affect the String.
   *
   * @param data character array
   * @param offset position (base 0) to start copying out of data
   * @param count the number of characters from data to copy
   * @return String containing the chars from data[offset..offset+count]
   * @throws NullPointerException if data is null
   * @throws IndexOutOfBoundsException if (offset &lt; 0 || count &lt; 0
   *         || offset + count &lt; 0 (overflow)
   *         || offset + count &gt; data.length)
   *         (while unspecified, this is a StringIndexOutOfBoundsException)
   * @see #String(char[], int, int)
   */
  public static String valueOf(char[] data, int offset, int count)
  {
    return new String(data, offset, count, false);
  }

  /**
   * Returns a String representing the character sequence of the char array,
   * starting at the specified offset, and copying chars up to the specified
   * count. Subsequent changes to the array do not affect the String.
   *
   * @param data character array
   * @param offset position (base 0) to start copying out of data
   * @param count the number of characters from data to copy
   * @return String containing the chars from data[offset..offset+count]
   * @throws NullPointerException if data is null
   * @throws IndexOutOfBoundsException if (offset &lt; 0 || count &lt; 0
   *         || offset + count &lt; 0 (overflow)
   *         || offset + count &gt; data.length)
   *         (while unspecified, this is a StringIndexOutOfBoundsException)
   * @see #String(char[], int, int)
   */
  public static String copyValueOf(char[] data, int offset, int count)
  {
    return new String(data, offset, count, false);
  }

  /**
   * Returns a String representation of a character array. Subsequent
   * changes to the array do not affect the String.
   *
   * @param data the character array
   * @return a String containing the same character sequence as data
   * @throws NullPointerException if data is null
   * @see #copyValueOf(char[], int, int)
   * @see #String(char[])
   */
  public static String copyValueOf(char[] data)
  {
    return copyValueOf (data, 0, data.length);
  }

  /**
   * Returns a String representing a boolean.
   *
   * @param b the boolean
   * @return "true" if b is true, else "false"
   */
  public static String valueOf(boolean b)
  {
    return b ? "true" : "false";
  }

  /**
   * Returns a String representing a character.
   *
   * @param c the character
   * @return String containing the single character c
   */
  public static String valueOf(char c)
  {
    // Package constructor avoids an array copy.
    return new String(new char[] { c }, 0, 1, true);
  }

  /**
   * Returns a String representing an integer.
   *
   * @param i the integer
   * @return String containing the integer in base 10
   * @see Integer#toString(int)
   */
  public static String valueOf(int i)
  {
    // See Integer to understand why we call the two-arg variant.
    return Integer.toString(i, 10);
  }

  /**
   * Returns a String representing a long.
   *
   * @param l the long
   * @return String containing the long in base 10
   * @see Long#toString(long)
   */
  public static String valueOf(long l)
  {
    return Long.toString(l);
  }

  /**
   * Returns a String representing a float.
   *
   * @param f the float
   * @return String containing the float
   * @see Float#toString(float)
   */
  public static String valueOf(float f)
  {
    return Float.toString(f);
  }

  /**
   * Returns a String representing a double.
   *
   * @param d the double
   * @return String containing the double
   * @see Double#toString(double)
   */
  public static String valueOf(double d)
  {
    return Double.toString(d);
  }

  /**
   * If two Strings are considered equal, by the equals() method, 
   * then intern() will return the same String instance. ie. 
   * if (s1.equals(s2)) then (s1.intern() == s2.intern()). 
   * All string literals and string-valued constant expressions 
   * are already interned.
   *
   * @return the interned String
   */
  public String intern()
  {
    return VMString.intern(this);
  }

  /**
   * Return the number of code points between two indices in the
   * <code>StringBuffer</code>.  An unpaired surrogate counts as a
   * code point for this purpose.  Characters outside the indicated
   * range are not examined, even if the range ends in the middle of a
   * surrogate pair.
   *
   * @param start the starting index
   * @param end one past the ending index
   * @return the number of code points
   * @since 1.5
   */
  public synchronized int codePointCount(int start, int end)
  {
    if (start < 0 || end >= count || start > end)
      throw new StringIndexOutOfBoundsException();

    start += offset;
    end += offset;
    int count = 0;
    while (start < end)
      {
	char base = value[start];
	if (base < Character.MIN_HIGH_SURROGATE
	    || base > Character.MAX_HIGH_SURROGATE
	    || start == end
	    || start == count
	    || value[start + 1] < Character.MIN_LOW_SURROGATE
	    || value[start + 1] > Character.MAX_LOW_SURROGATE)
	  {
	    // Nothing.
	  }
	else
	  {
	    // Surrogate pair.
	    ++start;
	  }
	++start;
	++count;
      }
    return count;
  }

  /**
   * Helper function used to detect which characters have a multi-character
   * uppercase expansion. Note that this is only used in locations which
   * track one-to-many capitalization (java.lang.Character does not do this).
   * As of Unicode 3.0.0, the result is limited in the range 0 to 2, as the
   * longest uppercase expansion is three characters (a growth of 2 from the
   * lowercase character).
   *
   * @param ch the char to check
   * @return the number of characters to add when converting to uppercase
   * @see CharData#DIRECTION
   * @see CharData#UPPER_SPECIAL
   * @see #toUpperCase(Locale)
   */
  private static int upperCaseExpansion(char ch)
  {
    return Character.direction[Character.readChar(ch) >> 7] & 3;
  }

  /**
   * Helper function used to locate the offset in upperExpand given a
   * character with a multi-character expansion. The binary search is
   * optimized under the assumption that this method will only be called on
   * characters which exist in upperSpecial.
   *
   * @param ch the char to check
   * @return the index where its expansion begins
   * @see CharData#UPPER_SPECIAL
   * @see CharData#UPPER_EXPAND
   * @see #toUpperCase(Locale)
   */
  private static int upperCaseIndex(char ch)
  {
    // Simple binary search for the correct character.
    int low = 0;
    int hi = upperSpecial.length - 2;
    int mid = ((low + hi) >> 2) << 1;
    char c = upperSpecial[mid];
    while (ch != c)
      {
        if (ch < c)
          hi = mid - 2;
        else
          low = mid + 2;
        mid = ((low + hi) >> 2) << 1;
        c = upperSpecial[mid];
      }
    return upperSpecial[mid + 1];
  }

  /**
   * Returns the value array of the given string if it is zero based or a
   * copy of it that is zero based (stripping offset and making length equal
   * to count). Used for accessing the char[]s of gnu.java.lang.CharData.
   * Package private for use in Character.
   */
  static char[] zeroBasedStringValue(String s)
  {
    char[] value;

    if (s.offset == 0 && s.count == s.value.length)
      value = s.value;
    else
      {
	int count = s.count;
	value = new char[count];
	VMSystem.arraycopy(s.value, s.offset, value, 0, count);
      }

    return value;
  }
  
  /**
   * Returns true iff this String contains the sequence of Characters
   * described in s.
   * @param s the CharSequence
   * @return true iff this String contains s
   */
  public boolean contains (CharSequence s)
  {
    return this.indexOf(s.toString()) != -1;
  }
  
  /**
   * Returns a string that is this string with all instances of the sequence
   * represented by <code>target</code> replaced by the sequence in 
   * <code>replacement</code>.
   * @param target the sequence to be replaced
   * @param replacement the sequence used as the replacement
   * @return the string constructed as above
   */
  public String replace (CharSequence target, CharSequence replacement)
  {
    String targetString = target.toString();
    String replaceString = replacement.toString();
    int targetLength = target.length();
    int replaceLength = replacement.length();
    
    int startPos = this.indexOf(targetString);
    StringBuilder result = new StringBuilder(this);    
    while (startPos != -1)
      {
        // Replace the target with the replacement
        result.replace(startPos, startPos + targetLength, replaceString);

        // Search for a new occurrence of the target
        startPos = result.indexOf(targetString, startPos + replaceLength);
      }
    return result.toString();
  }
}