import IncomparableException;

/**
 * Objects that can compare pairs of objects (for equality and
 * ordering).  Typically used to help with sorting.
 *
 * @author Chris Kern
 * @author Erin Nichols
 * @author Joe Simonson
 * @author Samuel A. Rebelsky
 * @version 1.1b5 of October 1999
 */
public interface Comparator {
    /** 
     * Determine if the first element is strictly smaller than the 
     * second.   Throws an exception if the two elements cannot
     * be compared.
     */
    public boolean lessThan(Object first, Object second)
        throws IncomparableException;
    
     /** 
     * Determine if the first element is strictly larger than the 
     * second.   Throws an exception if the two elements cannot
     * be compared.
     */
   
    public boolean greaterThan(Object first, Object second)
        throws IncomparableException;

    /** 
     * Determine if the first element is equal to the second.   Throws
     * an exception if the two elements cannot be compared.
     */
    public boolean equals(Object first, Object second)

        throws IncomparableException;


} // interface Comparator