id.java

发布/订阅系统路由重配算法,可应用于ad hoc环境

/*
 * project: RebecaSim
 * package: util
 * file:    ID.java 
 * version: 0.1
 * date:    31.03.2005
 * 
 * This software is part of the diploma thesis "Ein adaptives Brokernetz 
 * für Publish/Subscribe Systeme".
 */
package util;

/**
 * The <code>ID</code> class provides identifier objects based on 
 * <code>long</code> values.
 * Assuming the same <code>IDGenerator</code> is used, each created 
 * <code>ID</code> object will be unique (unless the <code>long</code> 
 * value range is exhausted).
 * @version 0.1 31.03.2005
 * @author  Helge Parzyjegla
 */
public class ID implements Comparable{

	/** 
	 * The default <code>IDGenerator</code> providing the <code>long</code> 
	 * id-values for new <code>ID</code> objects.
	 */ 
	private static IDGenerator generator = new IDGenerator();
	
	/** The id value. */
	private long id;
	
	/**
	 * Creates a new ID using the default <code>IDGenerator</code>.
	 */
	public ID() {
		id = generator.getId();
	}
	
	/**
	 * Creates a new ID using the specified IDGenerator <code>generator</code>. 
	 * @param generator the <code>IDGenerator</code> to use.
	 */
	public ID(IDGenerator generator) {
		id = generator.getId();
	}
	
    /**
     * Compares this object to the specified object.  The result is
     * <code>true</code> if and only if the argument is not
     * <code>null</code> and is a <code>ID</code> object that
     * is based on the same <code>long</code> id-value as this object.
     * @param  o the object to compare with.
     * @return <code>true</code> if the objects are the same;
     *         <code>false</code> otherwise.
     */
	public boolean equals(Object o) {
		return ( (o instanceof ID) && (this.id == ((ID)o).id) ); 
	}

    /**
     * Returns a hash code for this <code>ID</code>.
     * The result is the exclusive OR of the two halves of the primitive
     * <code>long</code> value this <code>ID</code> object is based on.
     * So it is computed similarly to the hash code of a 
     * <code>Long</code> object.
     * @return a hash code value for this <code>ID</code> object.
     */
    public int hashCode() {
    	return (int)(id ^ (id >>> 32));
    }
	
    /**
     * Compares two <code>ID</code> objects by comparing the <code>long</code>
     * values numerically the <code>ID</code> objects are based on.
     * @param  id the <code>ID</code> object to compare to.
     * @return the value <code>0</code> if this <code>ID</code> is
     * 		   equal to the argument <code>ID</code>; 
     *         a value less than <code>0</code> if this <code>ID</code>
     *         is numerically less than the argument <code>ID</code>; 
     *         and a value greater than <code>0</code> if this <code>ID</code>
     *         is numerically greater than the argument <code>ID</code>.
     */
	public int compareTo(ID id) {
		return (this.id<id.id ? -1 : (this.id>id.id ? 1 : 0));
	}
	
    /**
     * Compares this <code>ID</code> object to another object.  If
     * the object is an <code>ID</code>, this function behaves like
     * <code>compareTo(ID id)</code>.  Otherwise, it throws a
     * <code>ClassCastException</code> (as <code>ID</code> objects
     * are comparable only to other <code>ID</code> objects).
     * @param  o the <code>Object</code> to compare to.
     * @return the value <code>0</code> if this <code>ID</code> is
     * 		   equal to the argument <code>ID</code>; 
     *         a value less than <code>0</code> if this <code>ID</code>
     *         is numerically less than the argument <code>ID</code>; 
     *         and a value greater than <code>0</code> if this <code>ID</code>
     *         is numerically greater than the argument <code>ID</code>.
     * @throws <code>ClassCastException</code> if the argument is not an
     *		   <code>ID</code>.
     * @see    java.lang.Comparable
     */
	public int compareTo(Object o) {
		return compareTo((ID)o);
	}

	/**
	 * Sets the default <code>IDGenerator</code> providing the 
	 * <code>long</code> id-values for new <code>ID</code> objects.
	 * @param  generator the <code>IDGenerator</code> to use.
	 * @throws <code>IllegalStateException</code> if the argument is 
	 *         <code>null</null>.
	 */
	public static void setIDGenerator(IDGenerator generator) {
		if (generator == null) {
			throw new NullPointerException("IDGenerator cannot be set to " +
											"null.");
		}
		ID.generator = generator;
	}
	
	/**
	 * Resets the default <code>IDGenerator</code> to <code>0</code>.
	 */
	public static void resetIDGenerator() {
		generator.reset();
	}
	
	/**
	 * Resets the default <code>IDGenerator</code> to <code>value</code>.
	 * @param  value <code>long</code> value to set the default
	 *         <code>IDGenerator</code> to.
	 */
	public static void resetIDGenerator(long value) {
		generator.reset(value);
	}
	
	public long getValue() {
		return id;
	}
}