/*
* This program is free software; you can redistribute it and/or modify it under the
* terms of the GNU Lesser General Public License, version 2.1 as published by the Free Software
* Foundation.
*
* You should have received a copy of the GNU Lesser General Public License along with this
* program; if not, you can obtain a copy at http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html
* or from the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
* 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 Lesser General Public License for more details.
*
* Copyright (c) 2001 - 2013 Object Refinery Ltd, Pentaho Corporation and Contributors.. All rights reserved.
*/
package org.pentaho.reporting.libraries.serializer;
import java.io.Serializable;
import java.util.Comparator;
/**
* The class comparator can be used to compare and sort classes and their superclasses. The comparator is not able to
* compare classes which have no relation...
*
* @author Thomas Morgner
*/
@SuppressWarnings( "unchecked" )
public class ClassComparator implements Comparator<Class>, Serializable {
/**
* For serialization.
*/
private static final long serialVersionUID = -5225335361837391120L;
/**
* Defaultconstructor.
*/
public ClassComparator() {
super();
}
/**
* Compares its two arguments for order. Returns a negative integer, zero, or a positive integer as the first
* argument is less than, equal to, or greater than the second.<p>
* <p/>
* Note: throws ClassCastException if the arguments' types prevent them from being compared by this Comparator. And
* IllegalArgumentException if the classes share no relation.
* <p/>
* The implementor must ensure that <tt>sgn(compare(x, y)) == -sgn(compare(y, x))</tt> for all <tt>x</tt> and
* <tt>y</tt>. (This implies that <tt>compare(x, y)</tt> must throw an exception if and only if <tt>compare(y,
* x)</tt> throws an exception.)<p>
* <p/>
* The implementor must also ensure that the relation is transitive: <tt>((compare(x, y)>0) &&
* (compare(y,
* z)>0))</tt> implies <tt>compare(x, z)>0</tt>.<p>
* <p/>
* Finally, the implementer must ensure that <tt>compare(x, y)==0</tt> implies that <tt>sgn(compare(x,
* z))==sgn(compare(y, z))</tt> for all <tt>z</tt>.<p>
* <p/>
* It is generally the case, but <i>not</i> strictly required that <tt>(compare(x, y)==0) == (x.equals(y))</tt>.
* Generally speaking, any comparator that violates this condition should clearly indicate this fact. The
* recommended
* language is "Note: this comparator imposes orderings that are inconsistent with equals."
*
* @param c1 the first object to be compared.
* @param c2 the second object to be compared.
* @return a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater
* than the second.
*/
public int compare( final Class c1, final Class c2 ) {
if ( c1.equals( c2 ) ) {
return 0;
}
if ( c1.isAssignableFrom( c2 ) ) {
return -1;
} else {
if ( !c2.isAssignableFrom( c2 ) ) {
throw new IllegalArgumentException(
"The classes share no relation"
);
}
return 1;
}
}
/**
* Checks, whether the given classes are comparable. This method will return true, if one of the classes is
* assignable
* from the other class.
*
* @param c1 the first class to compare
* @param c2 the second class to compare
* @return true, if the classes share a direct relation, false otherwise.
*/
public boolean isComparable( final Class c1, final Class c2 ) {
return ( c1.isAssignableFrom( c2 ) || c2.isAssignableFrom( c1 ) );
}
}