constants.java

mysql集群

/*
 Copyright (C) 2002-2004 MySQL AB

 This program is free software; you can redistribute it and/or modify
 it under the terms of version 2 of the GNU General Public License as 
 published by the Free Software Foundation.

 There are special exceptions to the terms and conditions of the GPL 
 as it is applied to this software. View the full text of the 
 exception in file EXCEPTIONS-CONNECTOR-J in the directory of this 
 software distribution.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA



 */
/*
 * 	This program is free software; you can redistribute it and/or modify it under the terms of 
 * the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, 
 * or (at your option) any later version. 
 * 
 * 	This program is distributed in the hope that it will be useful, 
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  
 * See the GNU General Public License for more details. 
 * 	You should have received a copy of the GNU General Public License along with this program; 
 * if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */
package com.meidusa.amoeba.mysql.io;

/**
 * Represents various constants used in the driver.
 * 
 * @author Mark Matthews
 * 
 * @version $Id: Constants.java 6433 2007-05-18 18:38:56Z mmatthews $
 */
public class Constants {
	/**
	 * Avoids allocation of empty byte[] when representing 0-length strings.
	 */
	public final static byte[] EMPTY_BYTE_ARRAY = new byte[0];

	public final static byte[] SLASH_STAR_SPACE_AS_BYTES = new byte[] {
			(byte) '/', (byte) '*', (byte) ' ' };

	public final static byte[] SPACE_STAR_SLASH_SPACE_AS_BYTES = new byte[] {
			(byte) ' ', (byte) '*', (byte) '/', (byte) ' ' };

	/*
	 * We're still stuck on JDK-1.4.2, but want the Number.valueOf() methods
	 */
	private static final Character[] CHARACTER_CACHE = new Character[128];

	private static final int BYTE_CACHE_OFFSET = 128;

	private static final Byte[] BYTE_CACHE = new Byte[256];

	private static final int INTEGER_CACHE_OFFSET = 128;

	private static final Integer[] INTEGER_CACHE = new Integer[256];

	private static final int SHORT_CACHE_OFFSET = 128;

	private static final Short[] SHORT_CACHE = new Short[256];

	private static final Long[] LONG_CACHE = new Long[256];

	private static final int LONG_CACHE_OFFSET = 128;

	static {
		for (int i = 0; i < CHARACTER_CACHE.length; i++) {
			CHARACTER_CACHE[i] = new Character((char) i);
		}

		for (int i = 0; i < INTEGER_CACHE.length; i++) {
			INTEGER_CACHE[i] = new Integer(i - 128);
		}

		for (int i = 0; i < SHORT_CACHE.length; i++) {
			SHORT_CACHE[i] = new Short((short) (i - 128));
		}

		for (int i = 0; i < LONG_CACHE.length; i++) {
			LONG_CACHE[i] = new Long(i - 128);
		}

		for (int i = 0; i < BYTE_CACHE.length; i++)
			BYTE_CACHE[i] = new Byte((byte) (i - BYTE_CACHE_OFFSET));
	}

	/** Same behavior as JDK-1.5's Constants.characterValueOf(int) */
	
	public static Character characterValueOf(char c) {
		if (c <= 127) {
			return CHARACTER_CACHE[c];
		}

		return new Character(c);
	}

	/** Same behavior as JDK-1.5's Byte.valueOf(int) */

	public static final Byte byteValueOf(byte b) {
		return BYTE_CACHE[b + BYTE_CACHE_OFFSET];
	}

	/** Same behavior as JDK-1.5's Integer.valueOf(int) */

	public static final Integer integerValueOf(int i) {
		if (i >= -128 && i <= 127) {
			return INTEGER_CACHE[i + INTEGER_CACHE_OFFSET];
		}

		return new Integer(i);
	}

	/** Same behavior as JDK-1.5's Constants.shortValueOf(int) */
	
	public static Short shortValueOf(short s) {

		if (s >= -128 && s <= 127) {
			return SHORT_CACHE[s + SHORT_CACHE_OFFSET];
		}
		
		return new Short(s);
	}

	/** Same behavior as JDK-1.5's Long.valueOf(int) */
	
	public static final Long longValueOf(long l) {
		if (l >= -128 && l <= 127) {
			return LONG_CACHE[(int) l + LONG_CACHE_OFFSET];
		}

		return new Long(l);
	}

	/**
	 * Prevents instantiation
	 */
	private Constants() {
	}
}