1 package org.riverock.dbrevision.db; 2 3 import java.util.Comparator; 4 import java.io.Serializable; 5 6 import org.riverock.dbrevision.annotation.schema.db.DbForeignKeyColumn; 7 8 /** 9 * @author Sergei Maslyukov 10 * Date: 28.11.2006 11 * Time: 17:31:51 12 * <p/> 13 * $Id$ 14 */ 15 public class DbFkComparator implements Comparator<DbForeignKeyColumn>, Serializable { 16 private static final DbFkComparator DB_FK_COMPARATOR = new DbFkComparator(); 17 18 public static DbFkComparator getInstance() { 19 return DB_FK_COMPARATOR; 20 } 21 22 /** 23 * Compares its two arguments for order. Returns a negative integer, 24 * zero, or a positive integer as the first argument is less than, equal 25 * to, or greater than the second.<p> 26 * <p/> 27 * The implementor must ensure that <tt>sgn(compare(x, y)) == 28 * -sgn(compare(y, x))</tt> for all <tt>x</tt> and <tt>y</tt>. (This 29 * implies that <tt>compare(x, y)</tt> must throw an exception if and only 30 * if <tt>compare(y, x)</tt> throws an exception.)<p> 31 * <p/> 32 * The implementor must also ensure that the relation is transitive: 33 * <tt>((compare(x, y)>0) && (compare(y, z)>0))</tt> implies 34 * <tt>compare(x, z)>0</tt>.<p> 35 * <p/> 36 * Finally, the implementer must ensure that <tt>compare(x, y)==0</tt> 37 * implies that <tt>sgn(compare(x, z))==sgn(compare(y, z))</tt> for all 38 * <tt>z</tt>.<p> 39 * <p/> 40 * It is generally the case, but <i>not</i> strictly required that 41 * <tt>(compare(x, y)==0) == (x.equals(y))</tt>. Generally speaking, 42 * any comparator that violates this condition should clearly indicate 43 * this fact. The recommended language is "Note: this comparator 44 * imposes orderings that are inconsistent with equals." 45 * 46 * @param o1 the first object to be compared. 47 * @param o2 the second object to be compared. 48 * @return a negative integer, zero, or a positive integer as the 49 * first argument is less than, equal to, or greater than the 50 * second. 51 * @throws ClassCastException if the arguments' types prevent them from 52 * being compared by this Comparator. 53 */ 54 public int compare(DbForeignKeyColumn o1, DbForeignKeyColumn o2) { 55 if (o1.getKeySeq()<o2.getKeySeq()) { 56 return -1; 57 } 58 else if (o1.getKeySeq()==o2.getKeySeq()) { 59 return 0; 60 } 61 return 1; 62 } 63 }